MANGO (Mangifera indica L. cv. Apple) FRUIT RESPONSE TO PREHARVEST BAGGING AND POSTHARVEST TREATMENT WITH 1-METHYLCYCLOPROPENE

Transcription

1 MANGO (Mngifer indic L. cv. Apple) FRUIT RESPONSE TO PREHARVEST BAGGING AND POSTHARVEST TREATMENT WITH 1-METHYLCYCLOPROPENE JOSPHAT MUNG ATIA RUNKUA MASTER OF SCIENCE (Food Science nd Posthrvest Technology) JOMO KENYATTA UNIVERSITY OF AGRICULTURE AND TECHNOLOGY 2009

2 Mngo (Mngifer Indic L. cv. Apple) Fruit Response to Prehrvest Bgging nd Posthrvest Tretment with 1-Methylcyclopropene Jospht Mung ti Runku A Thesis Submitted in Prtil Fulfillment for the Degree of Mster of Science in Food Science nd Posthrvest Technology in the Jomo Kenytt University of Agriculture nd Technology 2009

3 DECLARATION This thesis is my originl work nd hs not been presented for degree in ny other university. Signture. Dte Jospht Mung ti Runku This thesis hs been submitted for exmintion with our pprovl s university supervisors. Signture. Dte Prof. Frncis M. Mthooko JKUAT, Keny. Signture. Dte Dr. Christine A. Onyngo JKUAT, Keny. Signture. Dte Dr. Willis O. Owino JKUAT, Keny. i

4 DEDICATION To Eric. ii

5 ACKNOWLEDGEMENTS I express my sincere thnks to my supervisors; Professor F.M. Mthooko, for his wise dvise, guidnce nd support, Dr. C.A. Onyngo nd Dr. W.O. Owino for their vluble cdemic counsel. I thnk Mr. P. Krnj nd Mr. D. Voth for their guidnce in lbortory nlyses. I cknowledge Jomo Kenytt University of Agriculture nd Technology for sponsoring the reserch work through reserch grnt to Prof. F.M Mthooko, Prof. E.M Khngi nd Dr. C.A. Onyngo. Thnks lot to the Mngus s, the proprietor s of Penim Investiments for their pprovl to use their mngo orchrd in Ytt s the experimentl field. Above ll, I thnk the Almighty God for the wholesome helth nd strength through out the project. iii

6 TABLE OF CONTENTS DECLARATION... i DEDICATION... ii ACKNOWLEDGEMENTS... iii TABLE OF CONTENTS... iv LIST OF TABLES... x LIST OF FIGURES... xi LIST OF APPENDICES... xv LIST OF ABBREVIATIONS AND ACRONYMS... xvi ABSTRACT... xvii CHAPTER ONE INTRODUCTION Bckground informtion Mngo fruit industry Prehrvest nd posthrvest mngo fruit qulity... 2 iv

7 1.4 Economic vlue of mngo fruit industry in Keny Prehrvest bgging nd posthrvest 1-MCP tretment of fruits Problem sttement Rtionle nd justifiction Objectives Hypothesis... 9 CHAPTER TWO REVIEW OF LITERATURE Mngo fruit production in Keny Problems in Keny s mngo fruit production Poor gronomicl prctices Pests nd diseses Poor posthrvest hndling Poor mrketing nd stringent qulity requirements Physiologicl disorders of fruits peel Effect of prehrvest bgging on fruit qulity Mngement of mngo fruit pests, diseses nd disorders in Keny Mngo fruit growth nd ripening v

8 2.5.1 Fruit development nd mturtion Fruit ripening Mngo fruit qulity Techniques used in mngo fruit storge Posthrvest ppliction of 1-methylcyclopropene in fruits CHAPTER THREE MATERIALS AND METHODS Experimentl design, plnt mterils nd tretment during fruit growth Prehrvest smpling Posthrvest 1-methylcyclopropene tretment nd smpling Mesurements of fruit physicl prmeters Weight nd dimeter Fruit firmness Colour Anlyses of fruit physiologicl prmeters Ethylene production nd respirtion rtes Posthrvest weight loss Anlyses of fruit chemicl prmeters vi

9 3.6.1 Strch content Sucrose, fructose nd glucose contents Totl soluble solids content nd totl titrtble cidity Determintion of β-crotene content Totl nthocynin content Chlorophyll content Ascorbic cid content Minerl contents Sensory evlution Sttisticl nlysis CHAPTER FOUR RESULTS AND DISCUSSION Physiologicl nd physico-chemicl chrcteristics of the fruit during growth nd development Visul ppernce of the fruit Chnges in fruit physicl prmeters Fruit weight nd dimeter Chnges in fruit firmness Chnges in fruit pulp nd peel colour Chnges in fruit biochemicl composition Fruit peel chlorophyll content vii

10 Pulp crotenoids nd peel nthocynins content Strch nd sugr contents Titrtble cidity nd totl soluble solids Fruit scorbic cid content Chnges in selected minerls content Chnges in fruit physiologicl prmeters Respirtion rte Ethylene production rte Sensory qulity of fruits t hrvest Fruit Posthrvest Behviour nd Response to 1-Methylcyclopropene Tretment Chnges in fruit physicl prmeters Fruit pulp nd peel colour Fruit firmness Fruit chemicl chnges Fruits strch nd sucrose content Fruit glucose nd fructose contents Totl titrtble cidity nd totl soluble solids content Chlorophyll content of fruit peel Fruit ß-crotene nd nthocynins content Fruit scorbic content Chnges in fruit minerls content Chnges in fruit physiologicl prmeters viii

11 Fruit weight loss Fruit respirtion nd ethylene production rtes Fruit sensory qulity on ripening CHAPTER FIVE CONCLUSION AND RECOMMENDATIONS REFERENCES APPENDICES ix

12 LIST OF TABLES Tble 1: Minerl content in the peel nd pulp during growth nd development of bgged nd control mngo fruits Tble 2: Clcium nd Mgnesium content in the peel nd pulp of both bgged nd unbgged fruits, ech with nd without 1-MCP during posthrvest storge t 25±1 o C, RH 60±5% Tble 3: Potssium nd phosphorous content in the peel nd pulp of both bgged nd unbgged fruits, ech with nd without 1-MCP during posthrvest storge t 25±1 o C, RH 60±5% x

13 LIST OF FIGURES Figure 1: Amount of mngo fruit exports ( )... 4 Figure 2: Chnges in fruit weight nd dimeter during growth nd development of bgged nd unbgged mngo fruits Figure 3: Chnges in fruit firmness during growth nd development of bgged nd unbgged mngo fruits Figure 4: Chnges in pulp nd peel L vlue during growth nd development of bgged nd unbgged mngo fruits Figure 5: Chnges in pulp nd peel hue ngle during growth nd development of bgged nd unbgged mngo fruits Figure 6: Chnges in chlorophyll nd chlorophyll b content obgged nd control mngo fruits during growth nd development Figure 7: Chnges in totl chlorophyll content of bgged nd unbgged mngo fruits during growth nd development Figure 8: Chnges in pulp ß-crotene nd peel nthocynins content of bgged nd unbgged mngo fruit during growth nd development Figure 9: Chnges in strch nd sucrose content of bgged nd unbgged mngo fruits during growth nd development Figure 10: Chnges in glucose nd fructose content of bgged nd control mngo fruits during growth nd development Figure 11: Totl titrtble cidity nd totl soluble solids of bgged nd control mngo fruits during growth nd development xi

14 Figure 12: Chnges in scorbic content of bgged nd control mngo fruits during growth nd development Figure 13: Respirtion rte of bgged nd unbgged mngo fruits during growth nd development Figure 14: Sensory qulity scores on peel ppernce nd colour, nd overll cceptnce for bgged nd control mngo fruits t hrvest Figure 15: Chnges in pulp nd peel L vlues of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5% Figure 16: Chnges in pulp nd peel hue ngle of both bgged nd unbgged mngo fruit, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5% Figure 17: Chnges in firmness of both bgged nd unbgged fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5% Figure 18: Strch nd sucrose content of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5% Figure 19: Chnges in glucose nd frucrose content of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5% Figure 20: Totl titrtble cidity nd totl soluble solids content of both bgged nd unbgged mngo fruits, ech with nd without 1- xii

15 MCP tretment during posthrvest storge t 25±1 o C, RH 60±5% Figure 21: Chnges in chlorophyll nd b content of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5% Figure 22: Totl chlorophyll content of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5% Figure 23: The ß-crotene nd nthocynins content of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5% Figure 24: Chnges in scorbic cid content of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5% Figure 25: Percentge weight loss in bgged nd unbgged mngo fruits during posthrvest storge t 25±1 o C, RH 60±5% Figure 26: Respirtion rte nd pek ethylene production of both bgged nd unbgged mngo fruits, ech with nd without with 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5% Figure 27: Sensory qulity scores of bgged nd unbgged mngo fruits on full ripening, seven DAH xiii

16 LIST OF PLATES Plte 1: Mture green Apple mngo with rust... 7 Plte 2: Bgged nd control mngo fruits Plte 3: Mture green bgged nd unbgged fruits t hrvest Plte 4: Visul ppernce of unbgged (A) nd bgged (B) fruits t 9 nd 15 DAH, respectively Plte 5: Visible colour chnges of bgged mngo fruits, with nd without posthrvest 1-MCP (20 ppm) tretment nd storge t 25±1 o C, RH 60±5% Plte 6: Visible effects of trnspirtion wter loss on bgged (A) nd unbgged (B) mngo fruits t 9 DAH Plte 7: Unbgged (A) nd bgged (B) peel, nd unbgged (C) nd bgged (D) pulp ppernce of mngo fruit on ripening, 7 DAH (Storge: 25±1 o C, RH 60±5%) xiv

17 LIST OF APPENDICES Appendix I: Tomtoes untreted (A) nd treted (B) with 1-MCP (20 ppm) 7 dys fter hrvest (DAH) Appendix II: Sensory evlution form Appendix III: The Hunter s CIE (Commission Interntionle de l Eclirge) L* * b* system colour spce xv

18 LIST OF ABBREVIATIONS AND ACRONYMS AOAC ANOVA DAB DAH FW HPLC nm RH TSS TTA 1-MCP Anlysis of Officil Anlyticl Chemistry Anlysis of vrince Dys fter bloom Dys fter hrvest Fresh weight High performnce liquid chromtogrphy Millimolr Reltive humidity Totl soluble solids Totl titrtble cidity 1- Methylcyclopropene xvi

19 ABSTRACT This study investigted the effectiveness of prehrvest fruit bgging s control of Apple mngo rust, nd its influence on fruit growth physiology nd qulity t hrvest nd on ripening. Response of Apple mngo fruit to posthrvest 1-methylcyclopropene tretment ws lso investigted. Mngo (Mngifer indic cv. Apple) fruit trees were rndomly selected nd tgged for subsequent smpling t commercil frm in Ytt District, semi-rid region of Estern Province, Keny. Smpling nd nlyses commenced 14 dys fter bloom (DAB), nd fortnightly therefter up to hrvest time t 168 DAB. On-tree fruit bgging ws done t 70 DAB, just before mnifesttion of Apple mngo rust. Bgged nd unbgged fruits were subjected to smpling nd nlyses for physicl, physiologicl nd chemicl prmeters. After hrvest, both bgged nd unbgged fruits were ech divided into two equl sets of fruits, with nd without 1-MCP tretment t 20 ppm, nd subjected to nlysis for chnges in physicl, physiologicl nd chemicl prmeters during storge t 25±1 o C, 60±5% RH. Sensory evlution for fruit ppernce, colour, tste, texture rom nd overll cceptnce ws done t hrvest nd on ripening on 9-point hedonic scle using 15 untrined pnelists. Unbgged fruits hd significntly (p<0.05) fructose, glucose nd sucrose, nthocynin, ß-crotene nd scorbic cid contents t hrvest. Bgged fruits were more green t hrvest, with significntly (p<0.05) higher chlorophyll (b nd totl) contents, peel L* vlue (mesure of colour brightness), peel hue ngle (mesure of colour) nd strch content. However, the difference in pulp xvii

20 L vlues, totl titrtble cidity, totl soluble solids, respirtion rte, firmness, fruit weight, fruit equtoril dimeter nd minerls (C, Mg, K nd P) content between bgged nd unbgged fruits were not significntly (p>0.05) different t hrvest. No ethylene ws detected up to hrvest. Bgged fruits hd significntly higher sensoril score in peel colour nd ppernce, with no visible blemishes t hrvest. The unbgged fruit hd visible blckish brown blemishes due to rust. Bgging nd 1-MCP tretments hd slight effect on respirtion nd ethylene production rtes, though control unbgged fruits hd higher respirtion nd ethylene peks of ml CO 2 /Kg/h nd nl/kg/h, respectively. Neither bgging nor 1-MCP retrded fruit ripening. Fruits in ll the tretments reched full ripeness nd eting qulity t 7 dys fter hrvest (DAH). Bgged ripe fruits hd higher sensoril score on peel colour, ppernce nd overll cceptnce. The differences in tste, flvour nd texture between ripe bgged nd unbgged fruits were not significnt (p>0.05). Unbgged fruits hd higher posthrvest weight loss, shriveled erlier nd consequently, shorter posthrvest life of nine dys compred to 15 dys for bgged fruits. Loss of totl titrtble cidity, scorbic cid nd initil firmness ws retrded by 1- MCP (20 ppm). Prehrvest bgging ws effective in controlling Apple mngo rust. However, posthrvest 1-MCP tretment ws not effective in improving the posthrvest shelflife of Apple mngo hrvested 168 DAB. xviii

21 CHAPTER ONE 1.0 INTRODUCTION 1.1 Bckground informtion Mngo (Mngifer indic L.) fruit hs n ttrctive colour, delicious tste nd excellent nutritionl properties, mking it world choice fruit (Mitr nd Bldwin, 1997). The ripe mngo fruit is good source of vitmins A, C, nd folte, ntioxidnts, clcium, mgnesium, phosphorus nd potssium (Klr et l., 1995). It is consumed s fruit nd s processed product like nectr, sqush, pulp, juice, jm, jellies nd cnned slices (Klr et l., 1995). Mngo tree belongs to the fmily Ancrdicee which hs 75 gener nd 700 species (Lizd, 1993). The genus Mngifer includes 25 species (Griesbch, 2003) with edible fruits such s Mngifer cesi, M. foetid, M. odort nd M. pjng, lthough M. indic, the mngo, is the only species tht is grown commercilly on lrge scle. Mngo tree is believed to hve originted in the Indo-Burmese region (Lizd, 1993), but cn now be found growing in more thn 87 other countries throughout the tropicl nd subtropicl world (Klr et l., 1995). There re more thn 1,100 vrieties of mngoes grown round the world (Griesbch, 2003). However, they re ll grouped into two rces; one from Indi nd the other from Southest Asi (Griesbch, 2003). The Indin rce is intolernt to humidity, hs flushes of bright red new growth tht is subject to powdery mildew nd nthrcnose nd bers fruit with regulr shpe. The Southest Asin rce is tolernt of excess moisture, hs ple green or red 1

22 new growth nd is resistnt to powdery mildew. Its polyembryonic fruit is ple green nd of n elongted kidney shpe. Kenyn mngo vrieties, Apple, Boribo nd Ngowe re of Indin rce (Griesbch, 2003). 1.2 Mngo fruit industry Mjor mngo producing countries in the world in descending order include Indi, Chin, Thilnd, Mexico, Pkistn, Indonesi Philippines, Brzil, Nigeri, Egypt (FAO, 2003). The world mngo fruit mrket is very competitive, with qulity nd price being the determinnts. The leding world producers hve low production costs nd better mrket penetrtion (FAO, 2003). Lrge scle production mkes these producers to benefit from economies of scle nd rech high levels of productivity. Severl countries, both lrge nd smll mngo exporters, re gered towrds incresing their exports of mngoes due to incresing world demnd (FAO, 2003). Kenyn producers should im t producing high qulity mngo fruits nd reduce posthrvest qulity so s to survive the competition. 1.3 Prehrvest nd posthrvest mngo fruit qulity Prehrvest culturl prctices nd environmentl conditions during fruit development profoundly influence posthrvest performnce nd finl qulity (Lechudel nd Jos, 2007). Mngo fruit skin, flesh nd stone hve specific compositions tht pper to ccumulte wter nd dry mtter t different rtes, depending on environmentl conditions (Lechudel nd Jos, 2007). Accumultion of wter results from the blnce between incoming fluxes such s phloem nd xylem, nd outgoing fluxes such s trnspirtion (Ge nrd et 2

23 l., 2007). The mount of crbohydrtes supplied to tree fruits depends on the mount produced by lef photosynthesis, on sink demnd nd on the vilbility of the reserve pool (Ho, 1996). It is essentil to understnd how prehrvest culturl prctice influence source-sink reltionships involved in fruit growth before its doption. Mngo fruit is hrvested t erly or lte mture green stge depending of the distnce to the mrket (Lizd, 1993). After hrvest, mngo fruit ripens by undergoing mny physicochemicl chnges tht determine the qulity of the fruit purchsed by the consumer. Appernce nd eting qulity re the mjor sensory ttributes tht determine consumer cceptnce of mngo fruit (Mtebe et l., 2006). Fruit ppernce is influenced by bsence/presence of physicl, pthologicl nd physiologicl disorders. These disorders re lso the min culprits in posthrvest loss of fruits nd vegetbles (Chege et l., 1995) due to their detrimentl effect on fruit physiologicl nd biochemicl chnges during posthrvest hndling. The disorders induce rotting nd erly senescence leding to poor flvor nd rom (Mtebe et l., 2006). Eting qulity is mostly determined by sugrs:cid rtio together with texture nd flvour (Mtebe et l., 2006). The sugrs nd secondry compounds content during fruit development re minly dependent on the metbolism of unloded sugrs in the phloem nd the ccumultion of their metbolites. The chrcteristic flvour of fresh mngo fruit is complex interction between lrge number of voltile nd non-voltile components (Lizd, 1993). The 3

24 non-voltile compounds, for exmple, sugrs nd cids, re responsible for the sweetness nd trtness of the fruit; the voltile compounds, for exmple, esters nd ldehydes, re centrl in producing the distinctive fruity flvour (Shirtke nd Mrtinoi, 2007). Also present in the mngo fruit re polyphenols or tnnins, which re responsible for stringency (Lizd, 1993) 1.4 Economic vlue of mngo fruit industry in Keny Horticulturl crops were Keny s leding foreign exchnge erner in the yer 2007, rking in KSh billion ( Fruits contributed only 2.8% of totl export vlue of horticulturl produce from Keny, wheres cut-flower nd vegetbles contributed 65% nd 32.2% respectively. Mngo fruit is in the third position fter vocdo nd pssion fruit s the most importnt export fruit in Keny. Mngo exports (tonnes) Yer Fig 1. Amount of mngo fruit exports ( ). Dt source: HCDA export sttistics ( 4

25 However, exports hve declined during the lst decde (Fig 1) nd comprise of smll proportion of ntionl production. This hs been ttributed to pests, diseses nd physiologicl disorders (Nymbo et l., 2006) nd posthrvest losses (FAO, 2003). However, demnd for fresh mngo fruits in Europe nd the Middle Est hs been expnding (FAO, 2003). Kenyn producers cn combine selection of high qulity vrieties, novel production prctices like orgnic frming, the ltest posthrvest hndling techniques nd successful imge-building, including setting stndrds, to conquer substntil shre of profitble high-end mrket niches. Promoting cultivtion nd mrketing of such high qulity vrieties such s Apple should be ccompnied by more reserch on their optimum requirements during growth, hrvesting nd posthrvest hndling. Environmentl concerns nd minimum chemicl residue requirements by the led export mrkets clls for doption of non-chemicl methods, like on-tree fruit bgging to control pthologicl nd physiologicl disorders in mngoes. It is ginst this bckdrop tht the cultivr Apple mngo, on-tree fruit bgging nd posthrvest 1-methylcyclopropene (1-MCP) tretment were selected for this study. However successful doption of these two technologies will require further reserch on fruit, cultivr nd climte specificity. This study ims t contributing towrds successful doption of these two technologies on Apple mngo fruit production in Keny, tropicl climte. 5

26 1.5 Prehrvest bgging nd posthrvest 1-MCP tretment of fruits Pre-hrvest bgging of fruit is used commercilly in countries like Jpn nd Austrli in order to optimize fruit qulity through reduced physiologicl nd pthologicl disorders (Joyce et l., 1997) leding to improved ppernce (Hofmn et l., 1997b). On-tree bgging of individul fruits cretes microclimte within the bg for the fruit. Bgging is reported to be effective in control of insect pests (Kitgw et l., 1992), posthrvest pthogens in lychee fruits (Kooriykul nd Srdsud, 1997), nthrcnose nd stem-end rot in mngo fruit (Hofmn et l., 1997b), skin blemishes (Kitgw et l., 1992), bird dmge, friction nd discolourtion in pers (Amrnte et l., 2002b). Reduced pthologicl disorders by bgging in combintion with posthrvest 1- MCP tretment my hve multiple effect of improving mngo fruit shelf life. 1-MCP binds irreversibly to ethylene receptors, delys ripening nd improves posthrvest qulity of climcteric fruits (Sisler nd Serek, 1997). Low concentrtion of 1-MCP slows effect of ethylene in brod rnge of fruits, vegetbles nd floriculture crops due to very low dissocition constnts for the 1-MCP-binding site complex (Blnkenship nd Dole, 2003). 1-MCP delyed ripening onset on fruits such s vocdo (Jeong et l., 2003), bnn (Pelyo et l., 2003), mngo (Jing nd Joyce, 2000), nectrine (Dong et l., 2001), plum (Dong et l., 2002) nd spoddil (Quipping et l., 2006). 6

27 1.6 Problem sttement Apple mngo is highly susceptible to russet-like physiologicl disorder tht ffects the fruit during mturtion, nd is severe in humid wether, rendering the fruit unfit for fresh mrket due to development of brown blemishes on the fruit peel (Plte 1). The resulting unttrctive ppernce disqulifies the fruit from the export mrket due to stringent qulity requirements. Producers get low returns from such blemished fruits s the fruits re sold in the locl lowend fresh mrket nd to locl juice processors. Due to lck of loclly vlidted informtion on best control options for Apple mngo russet (commonly known s rust by Kenyn mngo growers), gribusiness oriented mngo growers hve tried use of brod-spectrum synthetic pesticides for its control, without success. However, prehrvest fruit bgging my control rust. Plte 1: Mture green Apple mngo with rust. 7

28 Mngo fruit is lso perishble nd posthrvest losses in Keny re very high due to indequte posthrvest technologies, but use of posthrvest 1-MCP tretment my improve the posthrvest shelf life nd reduce the loss. 1.7 Rtionle nd justifiction Agriculture is the min occuption for 85% of Keny s popultion. Increse in Kenyn popultion hs resulted in less lnd tht is clssified s rble. However, there re huge trcts of unutilized lnd in rid nd semi-rid res of Keny where commercil production of drought resistnt crops like mngo crop cn be done. It is with this reliztion tht the Government of Keny creted the ministry of Development of Northern Keny nd other Arid Lnds, ccompnied by huge investments in improving rod infrstructure nd wter for irrigtion. Good returns on these investments will be relized by promoting commercil frming of high potentil crops tht grow well in these res. Mngo fruit, especilly Apple mngo, is such high potentil crop in terms of high demnd in the domestic nd export mrkets (Nymbo et l., 2006). 1.8 Objectives The min objective of this study ws to investigte the influence of pre-hrvest bgging on fruit qulity t hrvest nd response to 1-MCP. The specific objectives were to investigte the: 1. Effectiveness of on-tree fruit bgging in control of Apple mngo fruit rust. 2. Influence of on-tree bgging on chnges in physicl, physiologicl nd biochemicl prmeters nd sensory qulity during fruit growth nd posthrvest period. 8

29 3. Effect of 1-MCP on posthrvest fruit qulity. 1.9 Hypothesis 1. On-tree bgging of Apple mngo fruit (Mngifer indic L.) will control rust nd result in improved fruit qulity t hrvest nd on ripening without ffecting fruit response to posthrvest 1-MCP tretment. 2. Posthrvest 1-MCP tretment will improve mngo fruit posthrvest shelflife. 9

30 2.0 REVIEW OF LITERATURE CHAPTER TWO 2.1 Mngo fruit production in Keny During the lst yers, commercil mngo production in Keny hs been developed bsed on loclly dpted nd imported cultivrs (Griesbch, 2003). Depending on cultivrs nd environmentl conditions, it tkes 90 to 160 dys fter flowering for Kenyn mngo to rech mturity (Griesbch, 2003). Mngo production in Keny is predominntly smllholder crop in the semi-rid res, often produced t subsistence level with minimum inputs in terms of crop mngement (Nymbo et l., 2006). Mngo orchrds re normlly smll, not exceeding five hectres of lnd (Nymbo et l., 2006). The min production res re Cost, Estern nd Centrl provinces, though miniml production is lso done in Rift Vlley nd Western Provinces. Apple mngo hs emerged s preferred cultivr in Keny for both domestic nd export mrket, followed by Ngowe nd Tommy Atkins (Nymbo et l., 2006). Apple mngo fruits re medium to lrge in size, nerly round in shpe nd hve rich yellow/ornge colour when ripe. The verge longitudinl nd equtoril dimeters mesure 9.7 cm nd 11 cm respectively, nd the men weight is 397 gm (Griesbch, 1992). Normlly, if not disesed, the skin is smooth nd thin, nd the juicy yellow flesh is of excellent flvour nd melting texture virtully free from fiber. The seed is reltively smll. This ttribute hs mde Apple mngo the preferred cultivr in Keny. The trees re 10

31 lrge/vigorous nd of pyriform growth hbit. However, the cultivr is susceptible to rust, nthrcnose, powdery mildew nd lternte bering (Griesbch, 1992). 2.2 Problems in Keny s mngo fruit production Poor gronomicl prctices Poor gronomicl prctices chrcterize the industry (Nymbo et l., 2006). Mngo trees require intensive cre during flowering to hrvesting, but smllholder mngo fruit frmers in Keny llocte minimum inputs in the crop mngement (Nymbo et l., 2006), resulting in low qulity nd quntity. The chemicl sprys used in conventionl growing re expensive for the smllholder frmers. Orgnic mngo fruit production hs not tken root in Keny, in spite of the better prices nd ever incresing demnd for orgniclly grown fruits Pests nd diseses Pests, diseses nd physiologicl disorders re big chllenge to mngo growers. Mngo fruit is susceptible to wide rnge of prehrvest nd posthrvest pests nd diseses. Fruit flies nd mngo seed weevil, both qurntine pests re the most dmging pests of mngoes in Keny (Griesbch, 1992). Other insect pests include phids, scles, melybugs, coconut bugs, mosquito bugs (Helopeltis spp.) nd mngo gllflies (Griesbch, 1992). Powdery mildew nd nthrcnose, both fungl diseses re the mjor mngo fruit diseses in Keny (Griesbch, 1992). 11

32 2.2.3 Poor posthrvest hndling The smllholder frmers nd middlemen hve indequte technologicl knowledge nd fcilities for effective posthrvest hndling of fresh fruits nd vegetbles. Poor hrvesting, snittion, pcking, rod infrstructure nd lck of cold-chin infrstructure hve resulted in poor qulity mngo fruit due to mechnicl, biologicl nd physiologicl dmge. Mngo processing in Keny is not expnding t n pprecible rte, with only negligible shre of totl production being processed (FAO, 2003) Poor mrketing nd stringent qulity requirements Mrketing of mngo fruits in Keny is not well coordinted, like in coffee nd te sectors where mrketing societies nd coopertives ply key role in produce mrketing. The frmers typiclly sell to brokers, export gents or locl trders. These tend to be unrelible trding prtners becuse they offer low unstble prices nd tke n unpredictble mount of produce. The requirement for complince with the GLOBALGAP Control Points nd Complince Criteri for ll fruits nd vegetbles destined for the Europen mrket nd qurntine restrictions by mny other export mrkets hve hindered mrket penetrtion by Kenyn exporters. This is complicted by bckground of poor gronomicl prctices in the industry (Nymbo et l., 2006). 12

33 2.2.5 Physiologicl disorders of fruits peel Apple mngo rust is so fr the only physiologicl disorder with economic significnce in Keny mngo fruit industry (Nymbo et l., 2006). Fruits peel my develop some physiologicl disorders during mturtion, leding to poor externl ppernce t hrvest. These peel disorders re given different nmes descriptions depending on fruit type nd mode of formtion nd mnifesttion; like cuticle crcking in cherry fruit (Knoche nd Peschel, 2006), russeting in citrus fruit (Albrigo nd Achor, 2002) nd lenticel discolourtion (Bezuidenhout et l., 2005; Tmjind et l., 1992) or rust (Nymbo et l., 2006) in mngo fruit. Development of these disorders is specific to climte nd wether (Albrigo nd Achor, 2002), nd cultivr (Knoche nd Grimm, 2008; Bezuidenhout et l., 2005; Tmjind et l., 1992). Environmentl fctors like high reltive humidity nd wetness (Knoche nd Grimm, 2008) nd physicl (Knoche nd Peschel, 2006) nd chemicl (Bezuidenhout et l., 2005; Tmjind et l., 1992) properties of the fruit cuticle interct to result in mngo fruit peel discolourtion. The formtion nd development of the physiologicl peel disorders in different fruits is ntomiclly different. Russeting in pple fruit is cused by periderm formed in response to dmge of epiderml cells (Fust nd Sher, 1972). Some mngo fruit cultivrs hve been reported to develop peel disorders during mturtion due to discolourtion of lenticels found on the fruit peel (Bezuidenhout et l., 2005; Tmjind et l., 1992), cusing n unttrctive drk brown colourtion tht my be wrongly ssocited with 13

34 pthogenic infections (Bezuidenhout et l., 2005). Apple mngo in Keny is susceptible to russet cused by periderm formtion (Nymbo et l., 2006), wheres Keitt nd Tommy Atkins in South Afric (Bezuidenhout et l., 2005) nd Nmdokmi in Thilnd re susceptible to discolourtion of lenticels. Antomicl nd histochemicl investigtions hve been done on formtion, development nd mnifesttion of lenticel discolourtion in mngo fruit by Bezuidenhout et l. (2005) nd Tmjind et l. (1992). The two hve similr generl physiologicl ccount, but differ slightly on ntomicl detils, probbly due to cultivr, climte nd methodology differences. Mngo fruit lenticels develop from ruptured stomt nd enlrge s the fruit grows due to stretching of the fruit surfce. Lenticels of non susceptible cultivrs hve been found to be insulted with thicker phellogen contining cuticle, hence protected from the ction of terpenes in fruit peel resin. The terpenes re voltile nd re ble to move out of the resin ducts vi the sublenticelullr cells to the outside of the fruit through the lenticels (Bezuidenhout et l., 2005). Action of the terpenes on the tonoplsts of the sublenticellulr cells cuse vcuolr bound phenols to come out nd rect with polyphenol oxidse present in the cell wlls to form quinones. The quinones ccumulte on the cell wlls s brown deposits visible from the outside s drk brown rust. Other reserchers hve implicted phenols in browning of plnt tissues. Phenols cn become oxidized to form drk coloured pigments (Tucker, 1993) 14

35 tht pper s physiologicl disorders. Most plnt cells, especilly on fruit skin, undergo enzymtic browning when cell contents re exposed to tmospheric oxygen (Amrnte et l., 2002b). Injured epiderml cells relese phenolic compounds (minly o-dihydroxy phenols) tht re enzymticlly oxidised by polyphenol oxidse (diphenol oxygen oxidoreductse or ctechol oxidse) to form unstble quinone compounds (Myer 1987). Susceptibility of mngo cultivr to the disorder my depend on the presence or bsence of these compounds (Bezuidenhout et l., 2005), the degree of lenticel protection by endogenous wx (Amrnte et l., 2002b). Russeting in Apple mngo my be by similr phenomenon. However, exct biochemistry, physicl nd/or physiologicl interctions, either singulrly or in synergy, between ntomicl fetures of susceptible mngo cultivrs nd high humidity/low tempertures conditions is not yet cler. Use of chemicl sprys to control fruit peel russeting or crcking hs not been successful (Albrigo nd Achor, 2002). However, on-tree fruit bgging hs produced smooth, shiny nd ttrctive per (Amrnte et l., 2002b), grpes (Signes et l., 2007) nd Keitt mngo (Hofmn et l., 1997b) fruits. Bgging of pers resulted in higher fruit tempertures during the dy, resulting in more uniform cuticle cover of the epidermis, less crcks in the cuticle nd lrger deposition of wxes on the cuticle (Amrnte et l., 2002). Therefore, bgging my control Apple mngo rust or lenticel discolourtion by inducing deposition of lenticel protecting wxes nd/or preventing crcking of the cuticle. 15

36 2.3 Effect of prehrvest bgging on fruit qulity Pre-hrvest bgging of fruits (like most other pre-hrvest prctices) my ffect hrvest nd posthrvest qulity of the fruit (Hofmn, 1997). Bgging increse humidity nd temperture (Amrnte et l., 2002) nd decrese light intensity (Hofmn, 1997) on the fruit. It lso reduces fruit trnspirtion wter loss (Amrnte et l., 2002; Joyce et l., 1997) during growth. Fctors tht reduce evpotrnspirtion by plnt orgns my reduce clcium ccumultion (Hofmn, 1997) on these orgns. Therefore, fruit bgging my influence xylem nd phloem fluxes, fruit crbon supply nd eventully the fruit qulity (Genrd et l., 2007). Fctors tht reduce rdition interception by fruit or subtending leves result in reduced soluble solids, nd often higher cidity (Hofmn et l., 1997). Vrying results on the effect of bgging on fruit qulity hve been reported. The vrince my be due to fruit type, cultivr difference, timing nd durtion of bgging, nd type of bgging mteril. Bgging hd no effect on fruit size of Senstion nd Kensington mngoes (Joyce et l., 1997) nd pers (Amrnte et l., 2000). However, Johns nd Scotts (1989) reported incresed fruit size in polythene bgged bnns nd Estrd (2005) reported reduced weight on six mngo cultivrs bgged with nti-virus mesh. Litchi fruits bgged with white polyethylene bgs three dys before hrvest hd lower levels of totl soluble solids nd totl titrtble cidity t hrvest, but no differences were found fter six dys of storge (YueMing et l., 2005). Ann et l. (1998) reported higher sugr content in mngo fruit bgged with white pperbg thn in fruit bgged with drk 16

37 pperbg. Joyce et l. (1997) reported reduced blush on the skin nd pler flesh for mngos bgged during fruit growth with nonperforted white opque plstic bgs thn for unbgged fruit or fruit bgged with pper bgs. Effective nd beneficil ppliction of pre-hrvest bgging on mngo fruit for qulity improvement will require n in-depth investigtion on its effects on fruit physiology, qulity t hrvest nd posthrvest period. Fruit qulity ttributes re lrgely determined before hrvest, while posthrvest tretments, t best, mintin qulity during product storge nd distribution. Therefore, the reltionship between production conditions nd posthrvest qulity needs to be well understood if mximum nd consistent qulity for the consumer is to be chieved. 2.4 Mngement of mngo fruit pests, diseses nd disorders in Keny Most of the mngo fruit frmers in Keny use conventionl mens of cultivtion, in which the principl mesures in control of mngo fruit pests, diseses nd physiologicl disorders is by use of chemicl sprys, orchrd snittion, chemicl bits nd pruning (Nymbo et l., 2006). Keny Orgnic Assocition Network (KOAN) nd Keny Institute of Orgnic Frming (KIOF) hve been promoting orgnic production for the lst few yers. None of the current control mesures in conventionl nd orgnic mngo frming in Keny hs been effective in the control of rust in Apple mngo. Frmers in Mrgu district, Centrl Province of Keny, re reported to be sprying the 17

38 fruit using mixture of sop nd white minerl oil to control the rust but the spry is not effective enough (Nymbo et l., 2006). 2.5 Mngo fruit growth nd ripening Fruit development nd mturtion Antomiclly, fruits re swollen ovries tht my lso contin ssocited flower prts. Fruit development follows fertiliztion, nd occurs simultneously with seed mturtion. Fruits re well orgnized orgns composed of cells from different tissues. The mngo fruit is composed of one or two seeds, surrounded by pericrp, itself composed of three tissues: the endocrp which is lignified; the mesocrp, which is composed of lrge mss of cells constituting the min prt of the fruit nd the epicrp (peel). Complex chin of biologicl processes such s cell division, differentition, size increse, metbolic trnsformtions nd vcuolr storge determine importnt qulity trits such s fruit size, sweetness, cidity nd nutritionl qulity (Gènrd et l., 2007). These biologicl processes re influenced by environmentl fctors such s light, temperture, humidity, nutrient supply nd plnt fctors such s genetic mke-up. Fruit growth strts fter bloom, with intensive cell division. Cell division is phse of exponentil cell prolifertive ctivity, followed by progressive decrese of this ctivity s cell division proceeds, nd then mitosis stops nd the cell popultion enter stge of cell enlrgement (Bertin et l., 2003). After the first phse of cell division, cell DNA endoredupliction boosts the cell sink 18

39 strength. Endoredupliction is n incomplete cell cycle tht leds to DNA redupliction with no cell division, thus incresing the cell nucler DNA content (Bertin, 2005). The mount of cytoplsm cell cn mke nd sustin is proportionl to the mount of DNA in the nucleus (Bertin, 2005). Amplifying genome size by endoredupliction contributes to incresing cell size (Gènrd et l., 2007). Cell division nd endoredupliction re importnt components of sink strength (Ho, 1996), s they set the size limit of cell (Ho, 1996). The rte of crbohydrte uptke by fruit cells is proportionl to their level of endoredupliction (Genrd et l., 2007). Cell differentition is speciliztion of cells to serve distinct roles. It determines tissue ppernce nd the intensity of cell division nd endoredupliction (Genrd et l., 2007). Cell size increse involves the increse in totl cytoplsmic mcromoleculr mss nd cell expnsion. Cell expnsion involves irreversible increse in cell volume through vcuoliztion (Bertin, 2005), uptke of wter nd photossimilte, nd the plstic deformtion of the cell wll (Gènrd et l., 2007). Fruit development is controlled by environmentl, genetic, nd plnt fctors. Environmentl fctors include temperture, light, nd ir humidity. Such fctors influence importnt processes such s cell cycle durtion, endoredupliction, photosynthesis, respirtion, trnspirtion, phloemic trnsport, nd metbolism (Gènrd et l., 2007). The plnt fctors influence fruit qulity through resource nd hormonl controls. The complex source (leves for crbon nd roots for wter) nd sink (orgns such s fruits) reltionships in plnts influence fruit growth (Ho, 1996), metbolism nd 19

40 qulity (Gènrd et l., 2007). Crbon is llocted in plnt orgns ccording to orgn demnds nd priority rules. Mintennce respirtion costs hve first priority, with vegettive nd reproductive growth being second nd third in priorities respectively (Genrd et l., 2007). Crbon llocted to fruit flesh is prtitioned into four sugrs (sucrose, sorbitol, glucose, nd fructose), strch nd structurl crbohydrtes (Genrd et l., 2003). In generl, young developing fruits re extremely cidic s they ccumulte orgnic cids such s mlic, citric nd trtric cid nd their ph is often below 3 (Shirtke nd Mrtinoi, 2007). Fruit cidity is complex process tht includes metbolic processes nd vcuolr trnsport (Lobit et l., 2002). The proton pump pumps protons into the vcuole, resulting in drop of ph while synthesis nd ccumultion of orgnic cids within the vcuole serves s buffer to mintin the low ph. Some fruits such s mngo tht ccumulte high mounts of cids exhibit incresing ccumultion of very high mount of sugrs, minly glucose, fructose nd sucrose during growth nd mturtion (Ued et l., 2000). The ph of mture fruits generlly increses during mturtion. Fruits do not tste cidic becuse lrge mounts of sugrs ccumulte during mturtion (Tucker, 1993). Mny mture grpe berries hve ph of bout 3.5, but they tste sweet becuse of the high mount of sugr ccumultion (Shirtke nd Mrtinoi, 2007). Citrte is the predominnt cid in mngo fruit (Lizd, 1993), with mlte (Ued et l., 2000) nd succinte (Mitr nd Bldwin, 1997) lso found in significnt quntities. 20

41 Compounds from secondry metbolism such s vitmins nd crotenoids re essentil for the nutritionl nd esthetic qulity of fruits (Genrd et l., 2007). Secondry compounds re responsible for the typicl colour nd flvour of fruits. Crotenoids, chlorophyll, nthocynin nd betlin define fruit colour while in most cses, blend between mny phenolics, flvonoids, lkloids nd terpenoids define fruit flvour (Shirtke nd Mrtinoi, 2007). Most of these secondry compounds re present in fruit tissue t concentrtions in the mm rnge nd others in even lower concentrtions (Lizd, 1993). Anthocynins re responsible for most of the red-purple colour of fruits (Lizd, 1993). Anthocynins re wter-soluble phenolic glycosides tht cn be found in the cell vcoules of fruit nd vegetbles, but re often in the epiderml lyers. They produce strong colours, which often msk crotenoids nd chlorophyll (Tucker, 1993). Phenolic compounds contribute to the stringency properties ssocited with fruit qulity (Lizd, 1993), nd the defense of plnt tissue ginst invding pthogens (Lizd, 1993). They re lso substrtes in chin of biochemicl rections triggered by mechnicl nd/or physiologicl dmge of cell wlls to form discolouring precipittes, e.g. quinones on the fruit pee (Bezuidenhout et l., 2005) Fruit strch is hydrolyzed during mturtion nd ripening (Tucker, 1993). The timing of hrvest is criticl fctor in determining rom production nd flvour development prticulrly for climcteric fruits where ripening is regulted by ethylene (Lizd, 1993). Enormous chnges in production of voltile compounds tht contribute to rom nd flvour chnges occur s 21

42 ripening progresses. However, fruit hrvested t n immture stge produce mny of these compounds t rtes too low to chieve chrcteristic flvour (Tucker, 1993). Erly hrvest is dvntgeous commercilly s softening is reduced during hndling nd trnsport but it comes t the expense of flvour development (Tucker, 1993). Mngoes ccumulte their crbohydrte requirement prior to ripening nd cn be hrvested t the mture green stge nd still ttin cceptble tste nd flvour on ripening (Klr et l., 1995) Fruit ripening Mngoes re climcteric fruits tht exhibit n utoctlytic ethylene production nd incresed respirtory ctivity fter hrvesting. However, mturtion of mngo fruit is ccompnied by ripening ssocited chnges such s decrese in strch (Klr et l., 1995) nd rupture force (Lizd, 1993), nd development of yellow colour in the pulp (Mitr nd Bldwin, 1997), indicting possible ripening inducing ethylene production prior to detchment. After hrvest, ripening fruit undergo mny physicochemicl chnges tht determine the qulity of the fruit purchsed by the consumer. Fruit ripening is geneticlly progrmmed event tht is chrcterized by number of biochemicl nd physiologicl processes tht lter fruit colour, rom, flvour, texture nd its nutritionl vlue. These ltertions re due to enzymtic brekdown of the cell wll, strch hydrolysis, sugr ccumultion nd reduction of orgnic cids nd phenolic compounds, including tnnins (Lizd, 1993). Ethylene is the mjor phytohormone implicted in inducement of ripening in fruits. The response of hrvested fruit nd vegetbles to 22

43 endogenously produced nd exogenously pplied ethylene re numerous nd vried, nd they cn be beneficil or detrimentl (Mitr nd Bldwin, 1997) depending on stnding point long the mrket chin. The brekdown of crbohydrte polymers is the lrgest quntittive chnge ssocited with ripening of mngo fruits, especilly the ner totl conversion of strch to sugrs, ltering both the tste nd texture of the fruit (Lizd, 1993). Hydrolysis of mngo fruit strch to formtion of sugr is ssocited with the ripening process, with glucose, fructose nd sucrose constituting most of the monoscchrides (Ued et l., 2000). Totl titrtble cidity decreses with fruit ripening (Ued et l., 2000), possibly due to orgnic cids being used s respirtory substrtes (Tucker, 1993). Colour chnge in ripening fruit hs been ssocited by the consumer with the conversion of strch to sugr nd the development of other desirble ttributes, such tht the correct skin colour is often ll tht is required for decision to purchse the fruit (Li et l., 1997). The loss of green colour due to degrdtion of the chlorophyll structure (Lizd, 1993) is the most common visible chnge in climcteric fruits during ripening. The disppernce of chlorophyll is ssocited with the synthesis nd/or unmsking of other preexisting pigments (Tucker, 1993). Most of these pigments re crotenoids tht re synthesized during the development stges on the fruit but remin msked by the presence of chlorophyll (Lizd, 1993). The chloroplsts in the fruit peel re converted 23

44 into chromoplsts, which re red or yellow pigments, while others cultivrs my show reddish blush becuse of nthocynin. End of fruit ripening is followed by senescence whereby nbolic rections re suppressed by degrdtive chnges leding to deth nd decy of the fruit tissue (Mitr nd Bldwin, 1997). Senescence is ctlyzed by posthrvest disorders cused by pthogenic, physiologicl or mechnicl dmge. Mngo fruit is highly susceptible to posthrvest pthologicl disorders nd extremes of temperture nd thus, posthrvest technologies should be designed for their control (Lizd, 1993). Temperture is n importnt fctor tht influences the deteriortion rte of hrvested commodities (Burdon, 1997). Respirtion genertes het s sugrs nd orgnic cids get oxidized. The higher the storge temperture, the higher the respirtion rte (Crisosto nd Gner, 2001). In climcteric fruit, low temperture cn be used to chieve dely in the onset of ripening. Lowering the temperture reduces the production of ethylene nd the rte of response of the tissues to ethylene (Wtkins, 2006). However, exposure of mngo fruit to undesirble low temperture results in chilling injury (Lizd, 1993). Wter is mjor component of hrvested mngo fruit. Wter loss is one of the min cuses of physiologicl weight loss nd deteriortion tht reduces the mrketbility of fresh fruits due to shriveling fter losing only smll percentge of their originl weight (Lizd, 1993). Fruit skin composition nd 24

45 structure, reltive humidity, fruit nd surrounding tmosphere temperture nd ir velocity ffect the rte of wter loss from fresh fruit (Amrnte nd Bnks, 2002). 2.6 Mngo fruit qulity Appernce nd colour (Rthore et l., 2007) nd eting qulity (Pelyo et l., 2003) re the two most importnt fctors influencing consumer cceptnce of fruit. Appernce is visul ssessment tht cn be mde on the bsis of size, shpe, colour, wilting nd shriveling, cultivr properties, mechnicl dmge nd pthologicl nd physiologicl disorders (Amrnte et l., 2002b). Texture chrcteristics of fruit edible tissue include juiciness nd crispness (Rthore et l., 2007). The texture of fruit is ffected by cellulr orgnelles, biochemicl constituents, wter content or turgor nd cell wll composition. Thus, ny externl fctor ffecting these trits cn modify texture nd cn, therefore, led to chnges in finl fruit qulity (Genrd et l., 2007). Flvour is ffected by development stge t hrvest, physiologicl bnormlities, storge conditions, microbil infections nd storge with other commodities with strong rom (Kder et l., 1978). Arom plys n importnt prt in the development of optiml eting qulity in most fruits nd results from synthesis of mny voltile orgnic compounds during the ripening phse (Tucker, 1993). Flvour gents for most fruits contin mixture of voltile cids, ldehydes, lcohols, esters nd terpenoids (Lizd, 1993). 25

46 Mngo fruit eting qulity is bsed on the scrcity of fibers, sweetness nd miniml turpentine tste (Griesbch, 1992). The flesh of most of the improved cultivrs is pech-like nd juicy, of melting texture nd more or less free from fiber (Griesbch, 2003). Demnd is for juicy, melting fruit, but tste nd rom components re lso very importnt. Vrious cultivrs hve chrcteristic tste nd rom tht producer country cn cpitlize on to offer superior cultivrs nd distinguish itself from the competition. Fruit tste nd flvour re defined by the type (Tucker, 1993) nd rtios (Genrd et l., 2007) of orgnic compounds in the fruit. Cultivrs with high sugr levels nd well blnced sugr: cid rtios re preferred (Rthore et l., 2007). Severl minerls re known to influence qulity, the most notble of these being clcium. Clcium ppliction or high fruit clcium concentrtion is often ssocited with reduced weight loss, incresed firmness, less disese, reduced susceptibility to chilling injury, physiologicl disorders nd blemishes such s skin splitting, nd slower ripening (Hofmn, 1997). 2.7 Techniques used in mngo fruit storge Mngoes re highly perishble tropicl fruit, with shelf life of 2 to 3 weeks t mbient temperture (Klr et l., 1995). The trde of mngo hs been significntly limited due to their short shelf life nd highly perishble nture (Rthore et l., 2007). Time of hrvest, storge temperture nd tmospheric conditions re key fctors in posthrvest physiology of the fruit. Hrvesting mngoes premturely will prevent fruit from reching full ripeness. Hrvesting 26

47 fruit t stges beyond mture green will reduce their shelf stbility nd shorten their fresh mrket life (Klr et l., 1995). Posthrvest tretments on mngo fruit depend on the trget mrket nd re imed t complying with qurntine restrictions, retrding ripening or inititing ripening t consumer point. Time nd distnce required to rech export mrkets necessitte subjection of mngo fruit to vrious posthrvest tretments such s cold storge, modified tmosphere, controlled tmosphere, therml tretments nd fungicidl sprys intended to lengthen their shelf life. Therml qurntine tretments involve heting the mngo fruit t specific temperture-time regime to kill lrve nd eggs of qurntine pests. Prolonged posthrvest life is lso chieved. Three common therml qurntine tretments include; vpour het tretment, forced hot-ir tretment nd hot wter immersion tretment. Hot wter tretment is the most preferred qurntine tretment becuse it is esily dptble by growers nd fruit distributors, uses short tretment times, is relible nd ccurte in the monitoring of fruit tempertures, is efficient in killing surfce decy orgnisms, nd clenses fruit surfce during tretment. However, tempertures bove 46 C hve been reported to produce excessive fruit dmge (Klr et l., 1995) including skin sclding, bnorml errtic yellow ptches of colour development with ripening, ccelerted skin colour development (yellowing), dmged lenticels nd ccelerted respirtion rtes during pre-climcteric period (Jcobi et l., 2001). Most of the chemicl qurntine tretments hve been phsed out due to sfety nd environmentl concerns. Cold storge of mngo is used to 27

48 prolong shelf life by slowing the metbolic rte of fruit (Klr et l., 1995). However, cold storge of mngo is limited by its susceptibility to chilling injury t storge nd trnsport tempertures below 13 o C (Lizd, 1993). Therefore, there is need to look for chep, convenient nd relible posthrvest tretment. Vrious chemicl compounds tht inhibit ethylene ction hve been found to dely onset of ripening or to retrd its progression in vrious fruits. These include; CO 2 (Mthooko et l., 2001), dizocyclopentdiene (Mthooko et l., 1997), 1-methylcyclopropene, cyclopropene nd 3, 3-dimethylcyclopropene (Sisler nd Serek, 1997). 1-methylcycloprepene (1-MCP) is seemingly the most promising (Sisler nd Serek, 1997) nd of interest in this study. 2.8 Posthrvest ppliction of 1-methylcyclopropene in fruits Fruit response to 1-MCP depends on vribles like cultivr differences nd degree of mturity (Wtkins, 2006). Its effect my lso depend on tissue, orgn nd mode of ction of ethylene biosynthesis (Sisler nd Serek, 1997). In ddition, ppliction technique, the exposure environment, nd the storge environment (if different from the exposure environment) influence effectiveness of 1-MCP (Wtkins, 2006). Advnces in fruit ripening prior to 1- MCP ppliction my reduce its effectiveness due to elevted levels of ethylene found during ripening in some fruit cultivrs (Wtkins, 2006). 1- MCP my potentilly improve the posthrvest shelflife of Apple mngo fruits. 28

49 3.0 MATERIALS AND METHODS CHAPTER THREE 3.1 Experimentl design, plnt mterils nd tretment during fruit growth. Mngo (Mngifer indic L. cv. Apple) trees were rndomly selected nd tgged in commercil frm in Ytt District, semi-rid prt of Estern Province of Keny during the September, Februry, 2008 seson. Fruits of equl ge were rndomly selected nd one set of 500 fruits bgged using Stndrd Krft pper bgs t 70 dys fter bloom (DAB) (Plte. 2). The bgs were fstened on the fruit pedicel using wire. The bottom edge corners of the bgs were perforted for ventiltion nd dringe. Another equl set of fruits ws not bgged (control). A seprte set of bgged nd unbgged fruits ws tgged nd used for monitoring chnges in fruit equtoril dimeter. The experiment ws completely rndomized design (CRD). Plte 2: Bgged nd control mngo fruits. 29

50 3.2 Prehrvest smpling Smpling of the fruits commenced t 14 DAB nd continued t 14 dy intervls therefter. Eighteen smples for weight mesurement, 30 smples for mesurement of fruit dimeter nd nine smples for nlysis of the other prmeters were used. Those fruit tht were visully of equl size nd free from defects were hrvested from ech of the previously tgged trees. The fruits were immeditely trnsported, cold stored (15 o C) nd nlyzed for chnges in physicl, physiologicl nd chemicl prmeters in the lbortories of the Deprtment of Food Science nd Technology, Jomo Kenytt University of Agriculture nd Technology (JKUAT). 3.3 Posthrvest 1-methylcyclopropene tretment nd smpling Using fruit peel colour s mturity index, fruits were hrvested t 168 DAB. The bgged nd control fruits were ech divided into two equl sets. One set from bgged fruits nd nother one from control were ech enclosed in seprte 12 litre irtight continers fitted with self-seling rubber septum. 1- MCP gs ws generted from Smrtfresh TM powder (Rohm nd Hs Co., Jpn) with 3.3% w/w 1-MCP ccording to mnufcturer s instructions. An irtight syringe ws used to inject 20 ppm of the 1-MCP gs into the continers contining the fruits. The 20 ppm 1-MCP concentrtion is the verge effective concentrtion for vrious studies on mngo fruit (Blnkenship nd Dole, 2003). Six smples from ech tretment were used for the nlysis. Fruits were rrnged into two blocks of bgged nd unbgged fruits in rndomized complete block design (RCBD), nd then nlyzed for 30

51 chnges in physicl, physiologicl nd chemicl prmeters every three dy intervl during storge t mbient conditions (Temperture; 25±1 o C nd RH 60±5%) for 15 dys. A set of 1- MCP treted nd untreted tomto fruits (Appendix 1) were set longside the mngo fruits to scertin the efficcy of the 1-MCP. 3.4 Mesurements of fruit physicl prmeters Weight nd dimeter Fruit weight ws determined using scientific blnce (Model Libror AEG- 220, Shimdzu Corp. Kyoto, Jpn). The fruit dimeter ws determined using veneer cliper (Model N 8 P, Mitutoyo, Jpn) Fruit firmness Firmness ws mesured long the equtoril region of the fruit using penetrometer (Model CR-100D, Sun Scientific Co. Ltd, Jpn) fitted with n 8 mm probe. Firmness is expressed s Newton (N) (Jing et l., 1999) Colour Colour of both the pulp nd peel ws mesured for both the red nd green sides of ech fruit using Minolt color difference meter (Model CR-200, Osk, Jpn) tht ws clibrted with white nd blck stndrd tile. The L*, * nd b* coordintes were recorded nd, * nd b* vlues converted to hue ngle (H ) ccording to Mclelln et l. (1995); Hue ngle (H ) = rctn (b/) (for + nd +b vlues) = rctn (b/) (for - nd +b vlues) 31

52 = rctn (b/) (for - nd b vlues) = rctn (b/) (for + nd b vlues) 3.5 Anlyses of fruit physiologicl prmeters Ethylene production nd respirtion rtes Depending on the size, known weights of mngo fruits were plced in plstic jrs rnging in volume from 500ml to 3000 ml nd whose covers were fitted with self-seling rubber septum for gs smpling. The fruits were incubted for n hour t room temperture (22-26 o C). Gs smples from the hedspce gs were withdrwn using n irtight syringe nd injected into gs chromtogrphs (Models GC-8A nd GC-9A, Shimdzu Corp., Kyoto, Jpn for respirtion nd ethylene production rtes, respectively). The gs chromtogrph for crbon dioxide determintion ws fitted with therml conductivity detector nd Poropk N column nd tht for ethylene determintion ws fitted with n ctivted lumin column nd flme ioniztion detector. Rte of crbon dioxide production is expressed s ml per kg per hr t stndrd tmospheric pressure while ethylene production is expressed s nl per kg per hr Posthrvest weight loss Weights of nine fruits from ech tretment were tken on ech smpling dy using scientific blnce (Model Libror AEG-220, Shimdzu Corp. Kyoto, Jpn). The initil weight (W 1 ) of ech fruit t dy 0 nd the weight of the 32

53 sme fruit (W 2 ) on ech smpling dy were noted. The following formul ws used to clculte the % weight loss: % weight loss = 100 x (W 1 - W 2 )/W Anlyses of fruit chemicl prmeters Strch content This ws done by the strch stining method. A slice from the equtoril region of the fruit ws dipped in iodine solution (2g of I 2 into 100ml of 0.01M KI solution), immeditely removed nd left to stnd for three minutes. The percentge of drk blue colourtion on the cut surfce ws rted s percentge fruit strch content using Cornell Strch Chrt (Wtkins et l., 2004) Sucrose, fructose nd glucose contents. Sugrs were nlyzed using AOAC method (1996). Ten grms of the fruit pulp ws refluxed in ethnol for one hour. The extrct ws then concentrted by rotry evportion nd diluted with 75% cetonitrile. Stndrd solutions of concentrtions 0, 1, 2, 3, 4 mg of sucrose, fructose nd sucrose/ml were prepred by dissolving into 75% cetonitrile. The stndrd solutions nd the smple extrcts were injected into High Performnce Liquid Chromtogrph (HPLC) (Model LC-10AS, Shimdzu Corp., Kyoto, Jpn) fitted with refrctive index detector nd hving the following conditions: Oven temperture - 35 o C, Flow rte: ml/min, Injection volume - 20 ul, Column - NH 2 P-50 E. A stndrd curve ws drwn nd used to quntify the sugrs content of the smples. 33

54 3.6.3 Totl soluble solids content nd totl titrtble cidity Totl soluble solids (TSS) content ws determined using n Atgo hnd refrctometer (Model 500, Atgo, nd Tokyo, Jpn) nd expressed s o Brix. Totl titrtble cidity (TTA) ws determined by titrtion with 0.1N NOH in the presence of phenolphthlein indictor. The TTA is expressed s % citric cid, the predominnt orgnic cid in mngo fruit (Ued et l., 2000) Determintion of β-crotene content The β-crotene content of the fruit pulp ws determined by modified chromtogrphic procedure (Heionen, 1990). A smple of 20 gm ws crushed in pestle with mortr. A sptul of hydroflorosupercel ws dded nd then extrction done using 50ml cetone until the residue becme white. Prtitioning ws done using 25ml of petroleum ether in seprting funnel. Sponifiction ws crried out by dding n equl mount of extrct in to 3ml of 10% KOH in methnol, nd few drops of 0.1% butylted hydrotoluene in petroleum ether. The mixture ws kept in the drk for 16 hours followed by wshing with wter in seprting funnel until it becme cler. Sodium sulphte (nhydrous) ws dded to remove wter nd further concentrtion done using rotry evportor. The ß-crotene stndrd solutions of concentrtions 10, 20, 40, 60 nd 80 ppm were prepred by dissolving into petroleum ether. The ß-crotene extrcts from the smples nd stndrd solutions were injected into the HPLC (Model LC-10AS, Shimdzu Corp., Kyoto, Jpn), hving the following conditions: Mobile phse (cetonitrile: methnol: dichloromethne = 70: 10: 20), Flow rte ml/min, Column - 34

55 ODS 150, Injection volume - 10µL, Oven temperture - 35 o C. The stndrd curve derived from the stndrd solutions ws used to determine the ß- crotene content of the smples Totl nthocynin content Totl nthocynin ws determined in the peel using modified ph differentil method (Meyers et l., 2003). Three grms of the smple ws ground nd diluted with 100ml of distilled wter nd sediment removed by centrifugtion. Two sets of the sme smple were diluted with equl volume of buffers of ph 1.0 nd ph 4.5 nd the bsorbnce mesured t 510nm nd 700nm using UV-Vis spectrophotometer (Model UV mini 1240, Shimdzu Corp. Kyoto, Jpn). Smples diluted with the ph 1.0 buffer were left to rest for 15 minutes before mesurements, wheres the smples diluted with the ph 4.5 buffer were redy for mesurement fter 5 minutes. The blnk consisted of the corresponding pure buffer solution. To correct for turbidity (hze) the bsorbnce t 700nm ws subtrcted from the bsorbnce t 510nm (the wvelength of mximum bsorption). To clculte the difference in bsorbnce between the smples the following formul ws used: ΔAbsorbnce = (A 510nm ph 1.0 A 700nm ph 1.0 ) (A 510nm ph A 700nm ph 4.5 ) Determintion of nthocynin content ws bsed on Lmbert- Beer s Lw: A = εcl A is the bsorbnce, which is mesured with spectrophotometer. L is the pth length in cm of the spectrophotometer cell. Most spectrometer cells hve pth length of 1cm. 35

56 ε is the molr bsorbnce or molr extinction coefficient., physicl constnt for moleculr species in given solvent system t given wvelength. C is the molr concentrtion. Rerrnging the Lmbert- Beer s Lw eqution nd multiplying by the moleculr weight (M) of the pigment, the concentrtion in milligrms per liter is determined s: C (mg/l) = ΔA/εL x M x 10 3 x D Where D is the dilution fctor, nd ΔA is the difference in bsorbnce of the smple t mximum bsorption (510nm) in the ph 1.0 nd ph 4.5 buffers Chlorophyll content The chlorophyll content ws determined by UV-Vis spectrophotometer (Model UV mini 1240, Shimdzu Corportion, Kyoto, Jpn) using the method of Arnon (1949). The chlorophyll ws extrcted with 80% cetone, nd totl chlorophyll, chlorophyll nd b contents clculted using the following McKinney s coefficients (McKinney, 1941) s follows: Totl chlorophyll content (μg/g) = 20.2A A 663 Chlorophyll content (μg/g) = 12.7A A 645 nd Chlorophyll b content (μg/g) = 22.9A A Ascorbic cid content The scorbic cid ws determined using the AOAC (1996) method. Five grms of the pulp ws ground nd diluted with 10% trichlorocetic cid (TCA) to 100 mrk of 100ml volumetric flsk. 2, 6-dichlophenolindophenol ws titrted to 10ml of the fruit pulp filtrte. Ascorbic cid ws clculted s: 36

57 Ascorbic cid, (mg/100g) = (A-B) X C X 100/S X (100/10) Where A = volume in ml of indophenol solution used in the smple. B = Volume in ml of indophenol solution used for the blnk. C = Mss in mg of scorbic cid equivlent to 1 ml of stndrd indophenol solution. S = Weight of the smple tken (g) 100/10 = totl extrction volume/volume of titrted smple Minerl contents Minerls were nlyzed using AOAC (1996) method. Three grms of the pulp nd peel were seprtely dried in the oven, shed in the muffle furnce nd diluted with 1% HCl. Mg, K nd C were nlyzed by Atomic Absorption Spectrophotometry (AOAC, 1996) method using n tomic bsorption spectrophotometer (Model AA-6200, Shimdzu Corp., Kyoto, Jpn). Phosphorus content ws determined using scorbic cid method with the UV- Vis spectrophotometer (Model UV mini 1240, Shimdzu Corp., Kyoto, Jpn). 3.7 Sensory evlution The sensory evlution of the bgged nd unbgged fruits t hrvest nd on ripening seven dys fter hrvest (DAH) ws done using 9 point hedonic scle (Appendix 2) nd pnel of 15 untrined judges. The ttributes evluted t hrvest were peel colour, ppernce nd totl cceptnce. Peel ppernce nd colour, pulp colour nd texture, rom, tste nd totl cceptnce were evluted for the ripe fruits. Mngo slices were t room 37

58 temperture, plced into 3-digit coded pltes nd presented in rndom order (Mtebe et l., 2006). 3.8 Sttisticl nlysis Dt ws presented s mens + stndrd devitions. Comprison of mens using t-test for prehrvest dt nd ANOVA for posthrvest dt, nd Lest Significnce Difference (LSD) for men seprtion ws done t p=0.05 using Genstt -Third Edition. 38

59 4.0 RESULTS AND DISCUSSION CHAPTER FOUR 4.1 Physiologicl nd physico-chemicl chrcteristics of the fruit during growth nd development Visul ppernce of the fruit Both bgged nd unbgged fruits ttined mturity t the sme time, nd were hrvested t 168 DAB. The peel of control fruits hd rust lesions, visible whitish colonies of fungl infection nd spots of reddish blush (Plte 3). Bgged fruits hd n unblemished peel with light green colour nd no reddish blush. Plte 3: Mture green bgged nd unbgged fruits t hrvest Chnges in fruit physicl prmeters Fruit weight nd dimeter Fruit weights nd dimeters for both bgged nd unbgged fruits displyed growth on single sigmoid curve (Fig. 2), with chnges in fruit weight showing four distinct stges of growth. 39

60 Unbgged fruits Bgged fruits (A) Fruit weight (g) Fruit dimeter (mm) Unbgged fruits Bgged fruits Dys fter bloom (B) Fig. 2: Chnges in fruit weight (A) nd dimeter (B) during growth nd development of bgged nd unbgged mngo fruits. The verticl brs represent SE of the men of 18 nd 30 replictes for fruit weight nd dimeter respectively. When bsent, the SE fll within the dimensions of the symbol. The rrow indictes when bgging tretment commenced. denotes period of no significnt difference between bgged nd unbgged fruits. 40

61 Mngo fruit growth follows single sigmoid pttern (Klr et l., 1995). Miniml increses in fruit weight chrcterized stge I, 0 to 28 DAB. The gin in fruit weight nd dimeter t this stge is due to cell division nd incresed cell mss (Bertin et l., 2003). A slow rte of gin in weight nd dimeter t stge I ws observed in bredfruit (Worrel et l., 1998). Incresed rte of weight gin chrcterized stge II, 28 to 56 DAB, possibly due to cell enlrgement nd formtion of intercellulr spces (Bertin et l., 2003). This stge represents period of mesocrp cell enlrgement (Worrell et l., 1998). After cell division ceses, fruit growth continues mostly by cell expnsion (Bertin et l., 2003). Fruit growth strts fter bloom, with intensive cell division, but the prolifertive ctivity of the cells slows s development proceeds (Ho, 1996). Then mitosis stops nd the cell popultion enter stge of cell enlrgement (Bertin et l., 2003). Stge III, 56 to 112 DAB, ws chrcterized by rpid gin in fruit weight nd dimeter. This my hve been due to mssive strch deposition (Ued et l., 2000). Incresed strch storge ws responsible for rpid weight gin of bredfruit during development (Worrell et l., 1998). Stge IV strted 112 DAB nd represents cestion of growth nd strt of mturtion (Klr et l., 1995). Bgging of fruit hd no significnt effect on both fruit weight nd dimeter. This could be due to bgging hving been done fter sink strength hd lredy been determined during the erly stges of fruit growth. Bgging hd no effect lso on weight nd of Kensington mngo (Joyce et l., 1997) nd per (Amrnte et l., 2002) fruits. 41

62 Chnges in fruit firmness Fruit firmness is n importnt qulity index during loding nd shipping. Bgged nd control fruits hd similr pttern of chnges in firmness (Fig. 3) Unbgged fruits Bgged fruits b Firmness (N) (C) Dys fter bloom Fig. 3: Chnges in fruit firmness during growth nd development of bgged nd unbgged mngo fruits. The verticl brs represent SE of the men of 9 replictes. When bsent, the SE fll within the dimensions of the symbol. The rrow indictes when bgging tretment commenced. nd b denotes period of non-significnt nd significnt difference, respectively between bgged nd unbgged fruits (p=0.05). There ws n increse in fruit firmness during growth nd development up to 112 DAB, followed by decline in the erly stges of mturtion up to 140 DAB, nd then n increse prior to hrvest. Increse in fruit firmness is due to synthesis nd deposition of structurl crbohydrtes such s pectin nd hemicelluloses in the cell wlls of the fruit epicrp (Genrd et l., 2003), while 42

63 decline in fruit firmness during mturtion is due to synergistic degrdtion ction of cell wll hydrolses (Chin et l., 1999) in concert with expnsins (Sne et l., 2005) on cell wll structurl crbohydrtes. Totl pectin content in Irwin mngo decresed during mturtion with concomitnt decrese in its flesh firmness (Ued et l., 2000). Increse in fruit firmness immeditely before hrvest ws contrry to observtions on mny mngo cultivrs. Tommy Atkins (Mdigu, 2007) nd Chiin Hwng No. 1 (Ued et l., 2001) mngo fruits firmness remined lmost constnt during mturtion up to hrvest. This my be due to vrietl differences in cell wll ultrstructure, pericrp structure nd culticulr lyer formtion (Lizd, 1993). Mssive wx deposits occur in some cultivrs during development of cuticle lyer on the peel s mngo fruit mtures (Petti et l., 2007). The cuticulr lyer in the fully mture Crbo mngo is well defined nd its ultrstructure cnnot be ltered even by overnight soking or rubbing with methnol or chloroform (Lizd, 1993). Chiin Hwng No. 1 mngoes were found to decline in pulp rupture force during mturtion (Ued et l., 2001). Bgged mngo fruit hd non-significntly (p>0.05) lower firmness t hrvest. This reflected possible differences in peel composition nd/or structure between the tretments. These results re t vrince with those found on pers (Amrnte et l., 2002). This indictes tht bgged mngo 43

64 fruits my be more susceptible to mechnicl dmge during loding nd shipping, nd led to dverse effects on mrketbility Chnges in fruit pulp nd peel colour Fruit colour is n importnt qulity ttribute. Colour my influence flvour recognition nd consumer perception. Chnges in fruit pulp nd peel brightness, s indicted by L* vlues, re shown in Fig. 4. Pulp L* vlues incresed up to mximum of nd 84.7 for bgged nd control fruits, respectively t 140 DAB, nd then declined until hrvest t 168 DAB. This decline coincided with colour chnge from white to whitish-yellow. A decline in pulp L* vlue from mturtion to ripening ws observed in Chiin Hwng No. 1 mngo fruit (Ued et l., 2001). There were no significnt difference (p>0.05) in pulp L* vlue between bgged nd unbgged fruits. Peel L* vlue for bgged fruit remined lmost constnt between 140 DAB nd 168 DAB while those for control declined to significnt (p<0.05) lower vlues t 154 nd 168 DAB. The * nd b* vlues were reported s hue ngle (H o ) s per the Hunter s colour system (Appendix III), nd not lone s they re not independent vribles (McGuire, 1992). A 90 o hue ngle represents yellow, 180 o represents bluish/green, 270 o represents blue, nd 0 o (360 o ) represents red/purple (McGuire, 1992). The pulp hue ngle for both bgged nd unbgged fruits declined throughout growth, development nd mturtion (Fig. 5 A), with no 44

65 89 87 Unbgged fruits Bgged fruits (A) Pulp L vlue Peel L vlue Unbgged fruits Bgged fruits b b (B) b Dys fter bloom Fig. 4: Chnges in pulp (A) nd peel (B) L vlue during growth nd development of bgged nd unbgged mngo fruits. The verticl brs represent SE of the men of 9 replictes. The rrow indictes when bgging tretment commenced. nd b denotes periods of non-significnt nd significnt differences, respectively between bgged nd unbgged fruits (p=0.05). 45

66 significnt differences (p>0.05) in ll the smpling dys. The declining hue ngle vlues during mturtion corresponded with colour shift from white to yellow. The pulp hue ngle vlue t 168 DAB for bgged nd control fruits were 99.8 o nd 98.8 o respectively, with visible whitish-yellow due to synthesis nd ccumultion of ß-crotenes. Peel hue ngle for bgged fruits incresed in nerly liner mnner up to 140 DAB, nd then declined slightly up to hrvest (Fig. 5 B). Peel hue ngle for control fruit incresed up to 140 DAB, but in n intermittent mnner with periods of slight decline t 84 nd 112 DAB. Results on fruit nthocynin content showed 112 DAB with the highest nthocynin content (Fig. 7B). Therefore, the decline in peel hue ngle in unbgged fruits (towrds or more red) t 112 DAB my hve been due to high levels of nthocynins (Signes et l., 2007) nd incresed redness (< hue ngle). Reduced redness (>hue ngle) in bgged grpes my hve been due to modifiction of the internl tmosphere (Signes et l., 2007) nd/or elevted temperture inside the bg (Amrnte et l., 2002), which retrded mturity nd reduced nthocynin ccumultion (Hofmn et l., 1997b). Results on fruit chlorophyll content indicte 84 DAB with reduced chlorophyll levels (Fig. 6) tht my hve been effectively msked by the ccumulting nthocynins to cuse colour shift towrd red (< hue ngle). A colour shift from green (-*) towrds red (+*) in grpe fruit led to decline in hue ngle (Signes et l., 2007). Loss of green colour (-* towrds +*) cused decrese in peel hue ngle during mturtion of Chiin Hwng No. 1 mngo fruit (Ued et l., 2001). 46

67 160 Unbgged fruits (A) Pulp hue ngle (H o ) Bgged fruits Peel hue ngle (H o ) Unbgged fruits Bgged fruits b b (B) b Dys fter bloom Fig. 5: Chnges in pulp (A) nd peel (B) hue ngle during growth nd development of bgged nd unbgged mngo fruits. The verticl brs represent SE of the men of 9 replictes. The rrow indictes when bgging tretment commenced. nd b denotes period of non-significnt nd significnt difference, respectively between bgged nd unbgged fruits (p=0.05). 47

68 Unbgged fruit exhibited bigger decline in peel hue ngle (degreening) during mturtion resulting in significnt (p<0.05) lower vlues t 154 nd 168 DAB, probbly due to more exposure to ctlyst of oxidtive degreening. These results conform to the results on chlorophyll content. Therefore, bgging (reduced light) incresed L* vlue nd hue ngle of mngo fruit peel t hrvest. Similr results were reported on pech fruit (Lewllen, 2000) who reported tht s one moves from the outside to the inside of the cnopy (reduced light), L* vlues, chromticity, nd hue ngles of pech fruit peel incresed. Cellulose bgged grpes presented higher vlues of lightness nd hue ngle, but lower vlues of redness, yellowness nd chrom, while the nonbgged grpes were slightly drker (<L*), more red (>*), with higher intensity of color (>C*) but were less blue (<b*) thn bgged smples (Signes et l., 2007) Chnges in fruit biochemicl composition Fruit peel chlorophyll content Chnges in chlorophylls nd b fruit contents re illustrted in Fig. 6. Bgged nd control fruits hd similr pttern of chnges in chlorophyll content with significnt differences (p<0.05) only t 98, 112 nd 140 DAB. A higher content of chlorophyll b ws observed in bgged fruits, with significnt differences (p<0.05) t 98, 112, 154 nd 168 DAB. Chlorophyll content ws higher thn chlorophyll b in the erly dys of growth in both bgged nd control fruits, wheres chlorophyll b content ws higher thn chlorophyll t hrvest. This implied tht chlorophyll degrded fster thn chlorophyll b 48

69 16 14 Unbgged fruits Bgged fruits b b (A) Chlorophyll content (mg/100g FW) b Unbgged fruits Bgged fruits b (B) Chlorophyll b content (mg/100g FW) b b b Dys fter bloom Fig. 6: Chnges in chlorophyll (A) nd chlorophyll b (B) content of bgged nd control mngo fruits during growth nd development. The verticl brs represent SE of the men of 9 replictes. When bsent, the SE fll within the dimensions of the symbol. The rrow indictes when bgging tretment commenced. nd b denotes period of non-significnt nd significnt difference, respectively between bgged nd unbgged fruits (p=0.05). 49

70 during mturtion. Chlorophyll ws preferentilly degrded reltive to chlorophyll b in Tommy Atkins mngo (Medlicott et l., 1986). Bgged fruits hd significntly (p<0.05) higher totl chlorophyll content t hrvest (Fig 7). Indeed, bgged fruits hd higher peel hue ngle (Fig. 5 B) nd visully greener (Plte 3) t hrvest. Decrese in chlorophyll content prior to hrvest is due to enzymtic degrdtion, resulting in unmsking of betcrotenes nd nthocynins (Tucker, 1993). This implies tht reduced rdition by bgging reduced the rte of chlorophyll degrdtion, nd limited the unmsking of the nthocynins leding to lck of the chrcteristic reddish-purple colourtion of Apple mngo. This my complicte use of bgged mngo fruit peel colour s mturity index nd consumer perception. However, improved ppernce by bgging (Plte 3) my counter the negtive effect on peel colour Once solubilised, chlorophyll cn be oxidized to the colourless purin nd chlorin products (Lizd, 1993). Bgging resulted in greener fruit lso in BC-2 Fuji pples (Fllhi et l., 2001), pers (Amrnte et l., 2002) nd grpes (Signes et l., 2007) Pulp crotenoids nd peel nthocynins content The β-crotene content ws initilly low, nd then incresed shrply from 98 DAB up to hrvest for both bgged nd unbgged fruits (Fig. 8 A). nthocynin content incresed up to mturity (112 DAB), the decresed up to hrvest (Fig. 8 B). Crotenoids re terpenoid compounds derived from cetyl vi the mevlonic cid pthwy. The β-crotene is synthesized in green nd 50

71 35 30 Unbgged fruits Bgged fruits b Totl chlorophyll content (mg/100 g FW) b b Dys fter bloom Fig. 7: Chnges in totl chlorophyll content of bgged nd unbgged mngo fruits during growth nd development. The verticl brs represent SE of the men of 9 replictes. When bsent, the SE fll within the dimensions of the symbol. The rrow indictes when bgging tretment commenced. nd b denotes period of non-significnt nd significnt difference, respectively between bgged nd unbgged fruits (p=0.05). ripening fruit (Lizd, 1993). The β-crotene content incresed from the mture green to the ripe stge for Tommy Atkins mngoes, (Mdigu, 2007). Unbgged fruits hd significntly (p<0.001) higher β-crotene levels thn bgged fruits. Reduced light exposure in bgged fruits my hve reduced β- crotene biosynthesis. Elevted temperture nd greter exposure to sunlight increse crotenogenesis (Dutt et l., 2005). Prehrvest bgging reduced nthocynins in Apple mngo, s lso reported in Keitt mngo (Hofmn et l., 1997b) nd Fuji pple (Fn nd Mttheis, 1998) 51

72 3 2.5 Unbgged fruits Bgged fruits b (A) Bet-crotene content (ug/g FW) b b Anthocynins content (mg/100g FW) Unbgged fruits Bgged fruits b (B) b Dys fter bloom Fig. 8: Chnges in pulp ß-crotene (A) nd peel nthocynins (B) content of bgged nd unbgged mngo fruit during growth nd development. The verticl brs represent SE of the men of 9 replictes. When bsent, the SE fll within the dimensions of the symbol. The rrow indictes when bgging tretment commenced. nd b denotes period of non-significnt nd significnt difference, respectively between bgged nd unbgged fruits (p=0.05). 52

73 fruits. Reduced red blush in bgged fruits my be due to modifiction of the internl tmosphere (Hofmn et l., 1997b) nd/or elevted temperture inside the bg (Amrnte et l., 2002), which retrds mturity nd reduces nthocynin ccumultion (Fn nd Mttheis, 1998). Prehrvest bgging of mngo fruits with perforted Krft pper bgs in this study might hve cused substntil modifiction of light bsorption by the fruit to cuse reduction in nthocynin synthesis nd/or ccumultion Strch nd sugr contents Fruit strch content incresed during growth nd development, but decresed during mturtion (Fig. 9 A). Sucrose content incresed up to hrvest in both bgged nd unbgged fruits (Fig. 9 B). There ws rpid increse in strch content between 42 nd 56 DAB, indicting rpid strch deposition, probbly due to high ctivity of sucrose synthse (Mrini et l., 1991). Strch ccumultion is slow initilly, but increses remrkbly during growth nd then decreses strikingly during mturtion of Chiin Hwng No. 1 (Ued et l., 2001) nd Irwin (Ued et l., 2000) mngo fruits. The decrese in strch levels during mturtion is due to hydrolysis by mylse (Ued et l., 2000). A similr pttern of chnges in strch content ws found on Tommy Atkins (Mdigu, 2007). At 140 DAB, bgged nd unbgged mngo fruits hd similr strch contents. However, t 168 DAB when fruits were hrvested, bgged mngoes hd significntly higher levels of strch (p<0.05). This implied tht the rte of strch hydrolysis ws lower in bgged fruits. 53

74 unbgged fruits bgged fruits Strch content (%) b 20 (A) Sucrose content (mg/100gm FW Unbgged fruits Bgged fruits b (B) Dys fter bloom Fig. 9: Chnges in strch (A) nd sucrose (B) content of bgged nd unbgged mngo fruits during growth nd development. The verticl brs represent SE of the men of 9 replictes. When bsent, the SE fll within the dimensions of the symbol. The rrow indictes when bgging tretment commenced. nd b denotes period of non-significnt nd significnt difference, respectively between bgged nd unbgged fruits (p=0.05). 54

75 Sucrose content for both bgged nd unbgged fruit incresed stedily initilly, then rpidly fter 84 DAB to become the predominnt sugr up to hrvest. Sucrose ccumultion prior to mturtion of fruits is due to direct phloem unloding (Genrd et l., 2007) wheres strch hydrolysis ws responsible for rpid increse in sucrose during mturtion (Lechudel et l., 2005; Ued et l., 2000; Lizd, 1993). Bgged fruits hd consistently lower sucrose levels tht were significnt (p<0.05) only t hrvest, possibly due to lower rte of strch hdrolysis. Fruit glucose levels declined up to the lowest level t 84 DAB, but incresed therefter up to 168 DAB (Fig. 10 A), wheres fructose content incresed continully 168 up to hrvest(fig. 10 B). The initil predominnce of glucose my reflect its preferentil synthesis from ssimilte due to its high requirement for metbolism in the young fruit (Worell et l., 1998). The lower levels of glucose in the ltter phse of fruit growth my be ttributed to reduced metbolism nd preferentil chnneling of ssimilte to sucrose (Genrd et l., 2007) nd strch (Worrell et l., 1998). Similr trends were observed in Tommy Atkins (Mdigu, 2007), Irwin (Ued et l., 2000) nd Dshehri (Klr et l., 1995) mngo fruits. The differences in fruit glucose levels were significnt (p<0.001) during mturtion nd t hrvest wheres fructose content ws significnt only t hrvest. 55

76 Unbgged fruits Bgged fruits b (A) 300 Glucose content (mg/100g FW) b b b Fructose content (mg/100g FW) Unbgged fruits Bgged fruits Dys fter bloom b (B) Fig. 10: Chnges in glucose (A) nd fructose (B) content of bgged nd control mngo fruits during growth nd development. The verticl brs represent SE of the men of 9 replictes. When bsent, the SE fll within the dimensions of the symbol. The rrow indictes when bgging tretment commenced. nd b denotes period of non-significnt nd significnt difference, respectively between bgged nd unbgged fruits (p=0.05). 56

77 The sum totl of ech of the three sugrs t hrvest were mg/100g FW (2.4%) nd mg/100g FW (2.1%) for unbgged nd bgged fruits, respectively. Lrge vritions in mngo fruit sugrs content hve been reported, probbly due to vrietl nd climtic differences. Mture green Lirf mngo fruit hd low totl sugr level of bout 85mg/100g FW (0.085%) (Lechudel et l., 2005) wheres Chiin Hwng No. 1 (Ued et l., 2001), Irwin (Ued et l., 2000) nd Dshehri (Klr et l., 1995) mngo fruits hd fr much higher levels of 6.3, 14 nd 9%, respectively Titrtble cidity nd totl soluble solids Totl titrtble cidity (TTA) decresed grdully from 70 to 168 DAB in both bgged nd control fruits (Fig. 11). This could hve been due to decrese in citric cid (Lechudel et l., 2005; Ued et l., 2000) s it got used up s respirtory substrte (Lizd, 1993) or trnsformed to other metbolites (Lobit et l., 2002). Totl titrtble cidity declined during mturtion of Irwin (Ued et l., 2000) nd Chiin Hwng No. 1 (Ued et l., 2001) mngo fruits, probbly due to n increse in citrte lyse ctivity (Ued et l., 2001). Citrte concentrtion incresed t the beginning of pech fruit growth minly due to its metbolism (Lobit et l., 2002). However, the concentrtion decresed fter mid-growth due to dilution effect of increse in fruit size (Lobit et l., 2002). Citrte metbolism, fruit growth nd hence citrte dilution slows during mturtion (Wu et l., 2007). Therefore, decrese in citrte content during mturtion my indicte degrdtion (Lobit et l., 2003). There ws no significnt difference (p>0.05) in TTA between bgged nd unbgged fruits 57

78 up to hrvest. Likewise, bgging hd no effect on totl titrtble cidity in pers (Amrnte et l., 2002) nd Keitt mngo fruits (Hofmn et l., 1997b), but cused significnt reduction of TTA in litchi fruit (Yueming et l., 2005). There ws stedy increse in totl soluble solids (TSS) for both bgged nd unbgged fruits, lthough slight decline ws observed between 84 nd 98 DAB. The decline could hve been cused by the dilution effect of high rinfll in the field round the time. Incresed wter supply reduced Breburn pple fruit sugrs by dilution effect (Mills et l., 1996). Continuous increse in TSS ws observed during growth of Irwin mngo fruit (Ued et l., 2000).Totl soluble solids in Tommy Atkins mngo fruits decresed during mid-growth, but incresed prior to hrvest (Mdigu, 2007). Increse in TSS is due to incresed ccumultion of reducing sugrs nd prtil brekdown of pectin nd celluloses (Worrell et l., 1998). Bgged fruits hd consistently lower TSS levels. Bgged pples hd lower TSS levels (Signes et l., 2007). However, studies hve shown tht bgging hs no effect on TSS in lychee (Tys et l., 1998), pers (Amrnte et l., 2002) nd Keitt mngo (Hofmn et l., 1997b). 58

79 Totl titrtble cidity (% citric cid) Unbgged fruits Bgged fruits (A) Totl soluble solids ( o Brix) Unbgged fruits Bgged fruits (B) Dys fter bloom Fig. 11: Chnges in totl titrtble cidity (A) nd totl soluble solids (B) of bgged nd control mngo fruits during growth nd development. The verticl brs represent SE of the men of 9 replictes. When bsent, the SE fll within the dimensions of the symbol. The rrow indictes when bgging tretment commenced. denotes period of no significnt difference between bgged nd control fruits. 59

80 Fruit scorbic cid content Ascorbic cid content of both bgged nd control fruits decresed rpidly prior to mturtion (Fig. 12). Bgged fruit hd stedy decrese in scorbic cid content during mturtion wheres tht of control fruit incresed slightly before finl decrese fter 154 DAB. Decrese in scorbic cid content my be due to oxidtive processes (Lee nd Kder, 2000). Indeed, unbgged fruits tht were more prone to oxidtive processes due to greter exposure hd more rpid decline in scorbic contents prior to mturtion nd hrvest. Ascorbic cid decresed in ripening pples nd mngoes but incresed in ripening pricots, peches, nd ppys (Lee nd Kder, 2000). Bgged fruits hd significntly (p<0.001) higher levels of scorbic cid prior to mturtion nd significntly (p<0.001) lower levels prior to hrvest. The mount nd intensity of light during the growing seson hs definite influence on the mount of scorbic cid formed in fruits (Lee nd Kder, 2000). Ascorbic cid is synthesized from sugrs supplied through photosynthesis in plnts. Outside fruit exposed to mximum sunlight contin higher mount of vitmin C thn inside nd shded fruit on the sme plnt (Lee nd Kder, 2000). In generl, the higher the light intensity during growth, the higher the scorbic cid content of plnt tissues (Lee nd Kder, 2000). Slight increses in scorbic content during mturtion of unbgged fruits my hve been due to net ccumultion resulting from incresed synthesis, possibly fvoured by incresing sugrs ccumultion nd mximum light exposure. 60

81 500 Unbgged fruits Bgged fruits 400 Ascorbic cid content (mg/100 g FW) b b b b Dys fter bloom Fig. 12: Chnges in scorbic content of bgged nd control mngo fruits during growth nd development. The verticl brs represent SE of the men of 9 replictes. When bsent, the SE fll within the dimensions of the symbol. The rrow indictes when bgging tretment commenced. nd b denotes period of non-significnt nd significnt difference, respectively between bgged nd unbgged fruits (p=0.05) Chnges in selected minerls content Clcium, mgnesium, potssium nd phosphorus contents of the pulp nd peel for both bgged nd non-bgged fruits during growth nd development re shown in Tble 1. Clcium content in the peel nd pulp of both bgged nd non-bgged fruits decresed during growth nd development. However, the peel hd higher clcium content thn the pulp. Declining levels my be due to dilution effect of increse in fruit size (Ding et l., 1995). Clcium content of 61

82 Tble 1: Minerl content in the peel nd pulp during growth nd development of bgged nd control mngo fruits. Minerl content (mg/100 g FW) Peel Pulp DAB Minerl Bgged Control Bgged Control 56 Clcium ND b 11.9 ±0.10 ND 12±0.19 Mgnesium ND 9.4±0.33 ND 8.9±1.09 Potssium ND 95.6±10.11 ND 89.6±9.64 Phosphorus ND 13.5±2.15 ND 16.7± Clcium ND 10.2 ±0.29 ND 2.2±0.50 Mgnesium ND 9.3±0.27 ND 8.3±0.50 Potssium ND 85.3±5.25 ND 76.5±10.5 Phosphorus ND 16.8±2.21 ND 18.1± Clcium 4.7±0.07 c 4.7 ±0.05 NS g 2.2± ±0.54 NS Mgnesium 9.0± ±0.05 NS 8.4± ±0.61 NS Potssium 65.3± ±2.05 NS 80.4± ±6.58 NS Phosphorus 15.7± ±0.25 NS 18.0± ±1.51 NS 98 Clcium 5.7 ± ±0.03 *** f 1.3± ±0.52*** Mgnesium 9.0± ±0.03 NS 6.3± ±0.44NS Potssium 50.4± ±2.08 NS 264.6± ±6.87 * d Phosphorus 18.2 ± ±0.90 NS 23.3± ±1.55 NS 112 Clcium 4.4 ± ±0.07 NS f 1.9± ±0.59* Mgnesium 14.3± ±0.07*** 9.2± ±0.07 NS Potssium 70.6± ±7.07 NS 462.6± ±9.14*** Phosphorus 20.9± ±1.16 NS 28.6± ±2.05 NS 140 Clcium 2.2 ± ±0.07 NS 1± ±0.01 NS Mgnesium 14.3± ±0.07*** 8.1± ±0.01** e Potssium 60.7± ±5.14 NS 110.0± ±9.54 NS Phosphorus 19.1± ±0.97 NS 23.5± ±1.74 NS 154 Clcium 2.2± ±0.03* d 1±0.02 1±0.02 NS Mgnesium 18.7± ±0.03*** 4.6± ±0.01 NS Potssium 59.5± ±4.46* 91.6± ±6.43 NS Phosphorus 17.7± ±1.03 NS 32.7± ±1.38 NS 168 Clcium 2.2± ±0.04 NS 1± ±0.01 NS Mgnesium 12.2± ±0.04* 2.1± ±0.02 NS Potssium 65.0± ±5.40 NS 79.3± ±4.18 NS Phosphorous 22.2± ±1.04 NS 26.0± ±1.45 NS Bgging tretment ws done t 70 DAB b ND denotes not determined. c Dt vlues re mens ± SE of nine replictes d * denotes significntly different, p<0.05. e ** denotes significntly different, p<0.01 f *** denotes significntly different, p< g NS denotes not significnt, p >

83 Lirf (Lechudel et l., 2005) nd Tommy Atkins (Mdigu, 2007) mngoes decresed during fruit development. Clcium is considered n immobile nutrient tht is supplied to the fruit minly during the period of cell division nd erly dys of growth (Slisbury nd Ross, 1992). The differences in clcium contents between bgged nd unbgged fruits were not significnt (p>0.05) for both peel nd pulp, probbly becuse bgging ws done fter the criticl period of clcium supply to the fruit (Joyce et l., 1997). The clcium content of fruit is of generl importnce in terms of posthrvest qulity (Hofmn, 1997). Fruit with higher clcium contents tend to hve higher mechnicl strength, longer shelf life, enhnced resistnce to disese nd lower incidence of physiologicl disorders (Joyce et l., 1997). Mgnesium content ws higher in the peel thn in pulp for both bgged nd control fruits. The differences in mgnesium content of the peel, but not tht of the pulp, between bgged nd unbgged fruits were significnt (p<0.05) during mturtion. Potssium is n importnt component of the buffer system in the vcuole (Lechudel et l., 2005). The potssium content of the peels decresed prior to mturtion, but remined nerly constnt from mturtion to hrvest in both bgged nd unbgged fruits. Potssium content in peel nd pulp ws higher thn mgnesium nd clcium contents. Lechudel et l (2005) reported tht K + represented more thn 80% of the ction pool in Lirf mngo fruit flesh, followed by C 2+ nd Mg 2+. Potssium contents of bgged nd unbgged fruits were significntly different (p<0.05) only t 154 nd 112 DAB for peel nd pulp, respectively. 63

84 Phosphorous is n importnt component of mny plnt compounds, including DNA, cell membrnes, nd energy-yielding intermedites of photosynthesis nd respirtion. Peel nd pulp phosphorous content incresed prior to mturtion of both bgged nd control fruits, but remined nerly constnt during mturtion. Phosphorous content of green house cucumber incresed slowly during erly stges of growth but incresed rpidly with incresing mturity (Ding et l., 1995). The phosphorous contents of both peel nd pulp between bgged nd unbgged fruits were not significnt (p>0.05). The potssium, mgnesium nd phosphorous re redily re-distributed within the plnt cnopy (Slisbury nd Ross 1992), nd their fruit contents my hve not been ffected by bgging. Generlly, bgging hd no effect on Apple mngo fruit minerl content. Similrly, bgging of per fruit hd no effect on minerls content (Amrnte et l., 2002). Fruit bgging is likely to offer resistnce to wter vpour movement, reduce the trnspirtionl flux of wter nd, therefore, of minerls to developing fruit (Amrnte et l., 2002) Chnges in fruit physiologicl prmeters Respirtion rte As shown in Fig. 13, the respirtion rte ws very high immeditely fter full bloom with vlue of ml CO 2 /Kg/hr t 14 DAB, nd then declined shrply to ml CO 2 /Kg/hr t 28 DAB. The differences in respirtion rte between bgged nd unbgged mngo fruits were not significnt (p>0.05). This compres well with studies on pers (Amrnte et l., 2002) tht gve 64

85 Unbgged fruits Bgged fruits Respirtion rte (ml CO 2/Kg/h) Dys fter bloom Fig. 13: Chnges in respirtion rte of bgged nd unbgged mngo fruits during growth nd development. The verticl brs represent SE of the men of 9 replictes. When bsent, the SE fll within the dimensions of the symbol. The rrow indictes when bgging tretment commenced. denotes period of no significnt difference between bgged nd unbgged fruits. similr results. The initil high respirtion rte ws probbly due to high cellulr ctivity s result of cell division nd differentition. The rte declined grdully to ml CO 2 /Kg/hr t 56 DAB, possibly due to endoredupliction, nd then remined lmost stedy therefter for both bgged nd control fruits. Similr observtions were found on Irwin mngo fruits (Ued et l., 2000). This implied reduction of the high energy needs of the fruit fter mitosis hd stopped Ethylene production rte No ethylene ws detected in both bgged nd control fruits up to hrvest. It is possible tht the ethylene produced ws too low for detection or production of 65

86 detectble levels ws for short period tht coincided with none of the smpling dys. Vrying observtions on ethylene production by growing mngo fruit hve been reported. Ethylene ws not detected in Tommy Atkins mngo fruits (Mdigu, 2007). Crbo mngoes hd detectble levels prior to full mturity but not t full mturity (Lizd nd Cu, 1990). Ethylene production my decrese s mngo fruit mtures, become undetectble prior to mturity nd repper upon ripening (Lizd, 1993). Mngo fruits produce very low levels of ethylene, though it is mong the most ethylene sensitive fruits (Mitr nd Bldwin, 1997) Sensory qulity of fruits t hrvest Sensory scores nd visul ppernce of bgged nd unbgged fruits re shown in Fig. 14 nd Plte 3, respectively. The bgged mngoes were rted significntly (P<0.05) superior in terms of ppernce, colour nd overll cceptbility. The peel of bgged fruits hd smooth texture nd blemish free light green colour, nd could hve been the reson for its higher rting on colour nd ppernce by the pnelists. Similr results were reported on pers (Amrnte et l., 2002). However, portions of unbgged fruit peel hd chrcteristic ornge colourtion tht probbly, could hve resulted in higher colour nd ppernce scores were it not for the presence of drk brown rust lesions. 66

87 6 5 b Unbgged fruits Bgged fruits b Score (9-point hedonic scle) b 1 0 Appernce Colour Acceptnce Sensory ttribute Fig. 14: Sensory qulity scores on peel ppernce nd colour, nd overll cceptnce for bgged nd control mngo fruits t hrvest. Rting ws done on 9-point hedonic scle (1-like extremely nd 9-dislike extremely). The verticl brs represent SE of the men of 15 replictes of pnelists. b denotes period of significnt difference (p=0.05) between bgged nd unbgged fruits. 67

88 4.2 Fruit Posthrvest Behviour nd Response to 1-Methylcyclopropene Tretment Ripening mngo fruits exhibited profound physicochemicl chnges tht re chrcteristic of climcteric fruits, though these chnges occurred before the climcteric pek nd pek ethylene production. Senescence of unbgged nd bgged fruits strted t 9 nd 15 DAH, respectively (Plte 4). Therefore, bgging improved posthrvest shelflife of Apple mngo fruit. A B Plte 4: Visul ppernce of unbgged (A) nd bgged (B) fruits t 9 nd 15 DAH, respectively. (Storge: 25±1 o C nd 60±5% RH. DAH = Dys fter hrvest) Chnges in fruit physicl prmeters Fruit pulp nd peel colour Intense colour chnges occurred immeditely fter hrvest in ll the tretments for both pulp nd the peel. The peel colour chnged from light green to full yellow by 8 DAH. However, bgged fruits hd more uniform yellowing (Plte 5). Therefore, bgging nd 1-MCP tretments did not hve ny visible effect 68

89 0 DAH 0 DAH 4 DAH 4 DAB Bgged fruits Bgged fruits Bgged fruit Bgged fruit Without 1-MCP with 1-MCP without 1-MCP with 1-MCP 6 DAH 6 DAH 8 DAH 8DAH Bgged fruits Bgged fruits Bgged fruits Bgged fruits Without 1-MCP with 1-MCP without 1-MCP with 1-MCP Plte 5: Visible colour chnges of bgged mngo fruits, with nd without posthrvest 1-MCP (20 ppm) tretment nd storge t 25±1 o C, RH 60±5%. DAH = Dys fter hrvest. 69

90 on fruit degreening. Nevertheless, 1-MCP treted fruit hd more uniform ripening. However, 1-MCP retrds degreening in guvs (Azzolini et l., 2005), bnns (Jing et l., 1999) nd spodill (Quiping et l., 2006) fruits. Pulp L vlues declined rpidly fter hrvest in ll the tretments, then followed by inconsistent chnges from 3 DAH (Fig. 15 A). Therefore, both bgging nd 1-MCP did not hve cler effects on the chnges in pulp L vlue during ripening of Apple mngo fruit. However, Azzolini et l., (2005) reported less intense pulp colour nd retrded degreening in Pedro Sto guv fruits treted with 1-MCP (300 nl/l). The fruit peel brightness (L* vlues) chnged slightly in ll tretments during storge (Fig. 15 B). The peel L vlue of Chiin Hwng No. 1 mngo fruit remined nerly constnt during ripening (Ued et l., 2001). However, bgged fruits with nd without 1-MCP tretment mintined their significntly (p<0.05) higher vlues, except t 9 nd 12 DAH. Pulp nd peel hue ngle decresed with storge time in ll the tretments (Fig. 16), nd colour chnged from whitish yellow to intense yellow, indicting incresed synthesis nd ccumultion of bet-crotene (Azzolini et l., 2005). There were no significnt differences (p>0.05) in pulp hue ngle vlues between ll the tretments. 70

91 Pulp L vlue Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP c bd c bc d (A) d Peel L vlue Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP bc bc bc c c bc (B) Dys fter hrvest Fig. 15: Chnges in pulp (A) nd peel (B) L vlues of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5%. The verticl brs represent SE of the men of six replictes. nd c denotes period of no significnt difference for bgging nd 1-MCP tretments, respectively, while b nd d denotes period of significnt difference for bgging nd 1-MCP tretments, respectively. 71

92 Pulp Hue ngle ( H o ) Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP c c c c c (A) c Peel Hue ngle (H o ) Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP bc c bd c bc (B) bc Dys fter hrvest Fig. 16: Chnges in pulp (A) nd peel (B) hue ngle of both bgged nd unbgged mngo fruit, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5%. The verticl brs represent SE of the men of six replictes. When bsent, the SE fll within the dimensions of the symbol. nd c denotes period of no significnt difference for bgging nd 1-MCP tretments respectively. b nd d denotes period of significnt difference for bgging nd 1-MCP tretments respectively. 72

93 Fruit firmness There ws rpid decrese in fruit firmness immeditely fter hrvest, but with significntly (p<0.05) more decrese in both bgged nd unbgged fruits without 1-MCP tretment (Fig. 17). Firmness of the fruits decresed grdully therefter. Fruits in ll the tretments reched eting softness on 6 DAH. Decrese in fruit firmness is due to the ction of cell wll hydrolses (Lohni et l., 2004) nd expnsins (Sne et l., 2005). Intense loss of firmness indicted high sensitivity of fruit softening to ethylene nd limited inhibition of this loss by 1-MCP. Bgging nd 1-MCP tretment significntly (p<0.05) reduced fruit softening up to 3 DAH, but not therefter. Filure by 1-MCP to inhibit firmness loss fter 3 DAH could be ttributed to rpid regenertion of more ethylene receptors. Plotto et l. (2003) reported inhibition of firmness loss in 1-MCP treted Tommy Atkins but not in Kent mngo fruits, nd suggested tht this my be ttributed to vriety difference or tht mngoes were subjected to tretment t n dvnced stge of mturity. 1-MCP reduced softening of Dshehri mngo (Sne et l., 2005), pech (Mthooko et l., 2001) nd bnns (Lohni et l., 2004) during the first 2-3 dys of storge, but not therefter. Bgging hd n effect on fruit response to 1-MCP t 3 DAH. The 1- MCP treted unbgged fruits hd significntly (p<0.001) higher firmness thn 1- MCP treted bgged fruits. 73

94 bc d Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP Firmness (N) c c c c Dys fter hrvest Fig. 17: Chnges in firmness of both bgged nd unbgged fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5%. The verticl brs represent SE of the men of six replictes. When bsent, the SE fll within the dimensions of the symbol. nd c denotes period of no significnt difference for bgging nd 1-MCP tretments respectively. b nd d denotes period of significnt difference for bgging nd 1-MCP tretments respectively. Unbgged fruits could hve hd better skin penetrtion by 1-MCP. Bgged per fruits stored t 20 o C lso hd lrger decrese in firmness (Amrnte et l., 2002). There ws no correltion between firmness nd weight loss. Thus, fruit softening ws due to cell wll disssembly nd not loss of turgor pressure, view expressed by Lizd (1993). 74

95 4.2.2 Fruit chemicl chnges Fruits strch nd sucrose content There ws rpid decrese in strch content nd rpid increse in sucrose content in ll the tretments during the first nine dys of storge (Fig. 18). Strch content reduced to zero percent t 9 nd 12 DAH for unbgged nd bgged fruits, respectively. This decrese in strch content is due to its hydrolysis by mylses leding to complete disppernce of strch grnules (Lizd, 1993). The decrese in fruit percent strch ws mtched by rpid increse in sucrose content, which ws the predominnt sugr. Sucrose contributed 57% of totl sugrs in ripe Keitt mngoes, with fructose nd glucose mking up 28 nd 15%, respectively (Medlicott nd Thompson, 1985). The sucrose content of Hden, Irwin, Kent nd Keitt mngo fruits incresed spectculrly during ripening, nd contributed to most to the increse in sweetness (Vzquez-slins nd Lkshminryn, 1985). Sucrose metbolism during mngo ripening is ccompnied by increse in sucrose synthetse nd invertse ctivities (Lim et l., 1999). The difference in percentge strch nd sucrose contents between bgged nd unbgged fruits, nd between 1-MCP treted nd untreted fruits were not significnt (p<0.05) during storge. However, 1-MCP slowed strch hydrolysis in Tommy Atkins mngo fruit (Plotto et l., 2003) nd Spodill fruits (Quipping et l., 2006). 75

96 % Strch content bc c (A) c bc Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP 10 0 c c Sucrose content (mg/100g FW) c (B) c Unbgged, control Unbgged, 1-MCP Bgged,control Bgged, 1-MCP c c c bc Dys fter hrvest Fig. 18: Chnges in strch (A) nd sucrose (B) content of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5%. The verticl brs represent SE of the men of six replictes. When bsent, the SE fll within the dimensions of the symbol. nd c denotes period of no significnt difference for bgging nd 1-MCP tretments respectively. b nd d denotes period of significnt difference for bgging nd 1-MCP tretments respectively. 76

97 Fruit glucose nd fructose contents Glucose nd fructose contents incresed with increse in DAH in ll the tretments, but decresed during senescence (12 nd 15 DAH) (Fig.19). Depending on cultivr, glucose nd fructose contents my increse simultneously with the increse in sucrose content or my hve grdul decline during mngo fruit ripening (Mitr nd Bldwin, 1997). Chiin Hwng No. 1 mngo fruit sucrose, fructose nd glucose contents incresed on ripening (Ued et l., 2001). The differences in fruit sugrs content between bgged nd unbgged fruits, nd lso between 1-MCP treted nd untreted fruits were not significnt (p<0.05) during ripening. The posthrvest fruit sugrs content levels (Fig. 18 B nd 19) were higher thn the prehrvest levels (Fig 8 B nd 9), with the four tretments reching levels of between 11.0 nd 12.5% t 9 DAH. Higher sugr levels hve been reported in ripe Amrpdi, Mllik nd Bishwnth mngo fruits (Hossin et l., 2001) with 26.85, nd 18.70% totl sugrs, respectively. The verge of totl free sugr content in Chiin Hwng No. 1 mngo fruit (Ued et l., 2001) ws bout 6.3% t hrvest nd 16.5% on ripening. The big vritions could be ttributed to vrietl difference. Signes et l. (2007) lso reported such high totl sugr levels in Blck Tble grpes, with nd 18.54% in bgged nd unbgged fruits, respectively. 77

98 Unbgged, control Unbgged,1-MCP Bgged,control Bgged,1-MCP c c (A) Glucose content (mg/100g FW) bc c c c Fructose content (mg/100g FW) Unbgged, control Unbgged, 1-MCP Bgged,control Bgged, 1-MCP c bc c d (B) bc c Dys fter hrvest Fig. 19: Chnges in glucose (A) nd frucrose (B) content of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5%. The verticl brs represent SE of the men of six replictes. When bsent, the SE fll within the dimensions of the symbol. nd c denotes period of no significnt difference for bgging nd 1-MCP tretments respectively. b nd d denotes period of significnt difference for bgging nd 1-MCP tretments respectively. 78

99 Totl titrtble cidity nd totl soluble solids content The percent TTA for ll the tretments decresed rpidly up to 6 DAH, then grdully therefter (Fig. 20 A). Totl soluble solids content incresed up to 12 DAH in ll the tretments (Fig. 20 B). A rpid decrese in TSS content ws observed t 12 DAH except for the 1-MCP treted bgged fruits. Increse in TSS in mngo fruit is due to brekdown of complex crbohydrtes into simple sugrs (Srnwong et l., 2003) nd solubilistion of cell wll pectins (Rthore et l., 2007). Bgging nd 1-MCP tretment did not hve ny effect on fruits TSS during ripening. Bgging did not ffect TSS content of Keitt mngo fruit (Hofmn et l., 1997b) but 1-MCP treted Tommy Atkin mngo fruits showed lower TSS due to reduced strch degrdtion (Plotto et l., 2003). Mngoes exhibit continuous decrese in cidity during ripening (Lizd, 1993) due citric cid, the predominnt cid being used s respirtory substrte (Rthore et l., 2007). Effect of prehrvest bgging on totl titrtble cidity during mngo fruit ripening ws not significnt (p>0.05). Similrly, bgging lychee fruit (Tys et l., 1998) did no ffect TTA during ripening. Bgged nd unbgged fruits treted with 1-MCP hd significntly (p<0.05) higher TTA compred to fruits not treted with 1-MCP (Fig. 19 A). 1-MCP tretment prevented ethylene-induced cidity loss in spodill (Quipping et l., 2006), tomtoes (Wills nd Ku, 2001) nd plums (Dong et l., 2002). However, Dong et l. (2002) found tht ppliction of 1-MCP did not ffect the content of TTA in pricot. Effects of 1-MCP on TTA my depend on fruit cultivr nd storge conditions (Blnkenship nd Dole, 2003). 79

100 Totl tirtble cidity (% citric cid) c d d d Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP d (A) c TSS content ( o Brix) c Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP bd c c c c (B) Dys fter hrvest Fig. 20: Chnges in totl titrtble cidity (A) nd totl soluble solids (B) content of both bgged nd unbgged mngo fruits, ech with nd without 1- MCP tretment during posthrvest storge t 25±1 o C, RH 60±5%. The verticl brs represent SE of the men of six replictes. When bsent, the SE fll within the dimensions of the symbol. nd c denotes period of no significnt difference for bgging nd 1-MCP tretments respectively. b nd d denotes period of significnt difference for bgging nd 1-MCP tretments respectively. 80

101 Chlorophyll content of fruit peel The chlorophylls nd b (Fig. 21 A nd B) nd totl chlorophyll (Fig. 22) contents of fruit peel decresed with storge time in ll the tretments. The decrese in chlorophyll content of ripening fruits is due to physico-chemicl degrdtion of chloroplsts in which the grnl membrne is lost (Lizd, 1993). A rpid loss of chlorophylls ws observed between 3 nd 6 DAH for chlorophyll nd during the first 3 DAH for chlorophyll b. Bgging nd 1- MCP tretment hd no significnt (p>0.05) effect on degrdtion of chlorophyll. However, their effects on chlorophyll b were significnt (p<0.05), with bgged nd 1-MCP-treted fruits hving higher contents up to 9 nd 6 DAH, respectively. Bgging nd 1-MCP tretment resulted in significntly (p<0.05) higher totl chlorophyll content up to 6 DAH (Fig. 21). However, these differences were not expressed physiclly s there were no visul differences in the yellowing process in ll the tretments (Plte 5). Contrry to these results, 1-MCP ws found to be n excellent inhibitor of degreening in bnns (Jing et l., 1999; Li et l., 1997), spodill (Quiping et l., 2006), vocdo (Hershkovitz et l., 2005; Jeong et l., 2003) nd tomtoes (Mostofi et l., 2003). 81

102 Chlorophyll content (mg/100g FW) bc c c Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP bd c (A) c bc Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP (B) Chlorophyll b content (mg/100g FW) bd bd bc c c Dys fter hrvest Fig. 21: Chnges in chlorophyll (A) nd b (B) content of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5%. The verticl brs represent SE of the men of six replictes. When bsent, the SE fll within the dimensions of the symbol. nd c denotes period of no significnt difference for bgging nd 1-MCP tretments respectively. b nd d denotes period of significnt difference for bgging nd 1-MCP tretments respectively. 82

103 8 7 6 bc Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP Totl chlorophyll content (mg/100g FW) bd bd c c c Dys fter hrvest Fig. 22: Chnges in totl chlorophyll content of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5%. The verticl brs represent SE of the men of six replictes. When bsent, the SE fll within the dimensions of the symbol. nd c denotes period of no significnt difference for bgging nd 1- MCP tretments respectively. b nd d denotes period of significnt difference for bgging nd 1-MCP tretments respectively Fruit ß-crotene nd nthocynins content The ß-crotene content of the fruit pulp incresed, wheres nthocynin content decresed with increse in storge time for ll the tretments (Fig. 23). Increse in ß-crotene content ws reported in ripening of Dosehri (Rthore et l., 2007) nd Tommy Atkins (Mdigu, 2007) mngoes. The decrese in ß - crotene content fter 12 DAH could hve been due to oxidtion. ß-crotene is highly unsturted nd susceptible to oxidtion (Rodriguez-Amy, 1999) when exposed to light. 83

104 B-crotene content (ug/100 g FW) c c Unbgged, control Unbgged,1-MCP Bgged,control Bgged,1-MCP c c c (A) 5 bc 0 Anthocynins content (mg/100g FW) bc bc bc Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP bc bc Dys fter hrvest c (B) Fig. 23: Chnges in ß-crotene (A) nd nthocynins (B) content of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5%. The verticl brs represent SE of the men of six replictes. When bsent, the SE fll within the dimensions of the symbol. nd c denotes period of no significnt difference for bgging nd 1-MCP tretments respectively wheres b denotes period of significnt difference for bgging tretment. 84

105 There ws no significnt difference (p>0.05) in ß-crotene content between bgged nd unbgged fruits, nd lso between fruits with nd without 1-MCP tretment. Similr observtions were mde on 1-MCP Pedro Sto guvs nd ttributed to lycopene biosynthesis being independent of ethylene production (Azzolini et l., 2005). In mny fruits dditionl ß-crotene nd lycopene is synthesized during ripening. The pthwy for ß-crotene biosynthesis shows lycopene s the precursor of ß-crotene (Lizd, 1993). Therefore, ß-crotene biosynthesis in mngo fruit in this study could lso hve been independent of ethylene nd 1-MCP. Anthocynins content of the fruit peel decresed with increse in storge time in ll the four tretments. Decrese in peel nthocynin content during storge ws lso reported in Tommy Atkins mngo fruit (Mdigu, 2007). Unbgged fruits hd significntly (p<0.05) higher nthocynin content t hrvest nd mintined the reltively higher contents throughout storge period. Tretment with 1-MCP hd no significnt (p>0.05) effect on nthocynin contents of the peel Fruit scorbic content Fruit scorbic decresed with increse in storge time for ll the tretments (Fig. 24), s lso reported in Hden, Irwin nd Keitt (Vzquez-Slins nd Lkshminryn, 1985) nd Tommy Atkins (Mdigu, 2007) mngo fruits. This decrese could hve been due to oxidtive degrdtion. Tretment with 1- MCP retrded degrdtion of scorbic cid in both bgged nd unbgged 85

106 bc bd Unbgged control Unbgged 1-mcp Bgged control Bgged 1-mcp Ascorbic cid content (mg/100g FW) bd d d d Dys fter hrvest Fig. 24: Chnges in scorbic cid content of both bgged nd unbgged mngo fruits, ech with nd without 1-MCP tretment during posthrvest storge t 25±1 o C, RH 60±5%. The verticl brs represent SE of the men of six replictes. When bsent, the SE fll within the dimensions of the symbol. nd c denotes period of no significnt difference for bgging nd 1-MCP tretments respectively. b nd d denotes period of significnt difference for bgging nd 1-MCP tretments respectively. fruits. Similr observtions were mde on spodill fruits (Quiping et l., 2006). However, unbgged fruits hd significntly (p<0.05) higher retention of scorbic cid when treted with 1-MCP. Bgging hd significnt effect (p<0.05) on mngo fruits scorbic cid content during ripening. Unbgged fruits without 1-MCP tretment hd significntly (p<0.05) lower scorbic cid content up to 9 DAH. Higher rtes of trnspirtionl wter loss nd respirtion 86

107 could hve exposed the unbgged fruits to higher rtes of oxidtive processes leding to higher loss of scorbic cid. Ascorbte oxidse hs been proposed to be the mjor enzyme responsible for enzymtic degrdtion of scorbic cid (Lee nd Kder, 2000). Adverse physicl, pthologicl nd chemicl stress increse scorbte oxidse leding to incresed degrdtion of scorbic cid (Loewus nd Loewus, 1987). Ascorbic cid is more stble in cidic conditions (Ngy, 1980) nd fruits with higher titrtble cidity will hve slower scorbic cid degrdtion. Tretment with 1-MCP cused fruits to hve higher cidity, nd my hve been the reson of their higher scorbic cid content Chnges in fruit minerls content Chnges in clcium, mgnesium, potssium nd phosphorous fruit pulp nd peel contents during posthrvest storge re shown in tbles 2 nd 3. There were no significnt chnges in fruit peel nd pulp clcium contents with increse in DAH. Bgging nd 1-MCP tretments did not hve significnt effects on fruit peel nd pulp clcium contents. The clcium content of plntin showed smll nd inconsistent increses during ripening (Ahenkor et l., 1996). Fruit peel nd pulp mgnesium content incresed slightly during ripening, nd bgging nd 1-MCP tretments did not hve significnt effect on its fruit levels. Chnges in potssium nd phosphorous fruit peel nd pulp content due to ripening were insignificnt nd the trends were inconsistent. Potssium content of flse horn plntin decresed by 1% with ripening, though significnt but inconsistent increses were observed for iron, copper nd zinc (Ahenkor et l., 1996). 87

108 Tble 2: Clcium nd Mgnesium content in the peel nd pulp of both bgged nd unbgged fruits, ech with nd without 1-MCP during posthrvest storge t 25±1 o C, RH 60±5%. Clcium nd Mgnesuim content (mg/100 g FW) Peel Pulp DAB Minerl Unbgged Unbgged Bgged Bgged Unbgged Unbgged Bgged Bgged Control 1-MCP control 1-MCP b Control 1-MCP control MCP 0 Clcium 2.3±0.04 c 2.3± ± ±0.01 c 1.1± ± ± ±0.02 c Mgnesium 10.3±0.04 c 10.3± ± ±0.02 bc 2.4± ± ± ±0.01 c 3 Clcium 2.3± ± ± ±0.01 c 2.3± ± ± ±0.02 c Mgnesium 11.8± ± ± ±0.14 c 2.5± ± ± ±0.28 c 6 Clcium 2.4± ± ± ±0.01 c 2.3± ± ± ±0.01 c Mgnesium 13.6± ± ± ±0.71 c 2.7± ± ± ±0.06 bc 9 Clcium 2.3± ± ± ±0.03 c 2.3± ± ± ±0.02 c Mgnesium 15.3± ± ± ±0.55 c 2.8± ± ± ±0.02 bc 12 Clcium 2.3± ± ± ±0.02 c 2.2± ± ± ±0.01 c Mgnesium 14.9± ± ± ±0.26 c 2.7± ± ± ±0.02 c 15 Clcium 2.4± ± ± ±0.02 c 2.4± ± ± ±0.01 c Mgnesium 15.9± ± ± ±0.28 c 2.7± ± ± ±0.04 c Bgging tretment ws done t 70 DAB. b 1-MCP tretment t 20 ppm ws done immeditely fter hrvest. c Dt vlues re mens ±SE of six replictes. nd c denotes not significntly different t p 0.05 for bgging nd 1-MCP tretments respectively while b denotes significntly different t p 0.05 for bgging tretment. 88

109 Tble 3: Potssium nd phosphorous content in the peel nd pulp of both bgged nd unbgged fruits, ech with nd without 1-MCP during posthrvest storge t 25±1 o C, RH 60±5%. Potssium nd phosphorous content (mg/100 g FW) Peel Pulp DAB Minerl Unbgged Unbgged Bgged Bgged Unbgged Unbgged Bgged Bgged Control 1-MCP control 1-MCP b Control 1-MCP control 1-MCP 0 Potssium 63.3±5.40 c 63.3± ± ±7.10 c 63.4± ± ± ±2.02 bc Phosphorous 22.4±1.04 c 22.4± ± ±1.41 c 25.4± ± ± ±1.88 c 3 Potssium 70.7± ± ± ±3.14 c 92.1± ± ± ±3.02 c Phosphorous 24.7± ± ± ±2.01 c 29.7± ± ± ±2.02 c 6 Potssium 80.9± ± ± ±4.09 c 85.7± ± ± ±6.94 c Phosphorous 27.4± ± ± ±1.81 c 28.7± ± ± ±2.14 c 9 Potssium 84.8± ± ± ±6.21 c 94.0± ± ± ±8.87 c Phosphorous 37.1± ± ± ±1.73 c 35.3± ± ± ±3.25 c 12 Potssium 83.0± ± ± ±2.92 c 96.2± ± ± ±6.80 c Phosphorous 26.4± ± ± ±2.22 c 33.9± ± ± ±2.01 c 15 Potssium 79.1± ± ± ±6.62 c 100.2± ± ± ±11.42 c Phosphorous 25.3± ± ± ±1.52 c 35.1± ± ± ±3.53 c Bgging tretment ws done t 70 DAB. b 1-MCP tretment t 20 ppm ws done immeditely fter hrvest. c Dt vlues re mens ±SE of six replictes. nd c denotes not significntly different t p 0.05 for bgging nd 1-MCP tretments respectively while b denotes significntly different t p 0.05 for bgging tretment. 89

110 Generlly, the minerls content of the fruits were low, nd this could hve reflected lck of fertilizer ppliction on the mngo trees. Low clcium levels in both pulp nd peel could hve been the cuse of fster softening of the fruits Chnges in fruit physiologicl prmeters Fruit weight loss Percentge fruit weight loss incresed with dys of storge in ll the tretments (Fig. 25). Posthrvest weight loss in mngo fruit is ttributed to physiologicl weight loss due to respirtion, trnspirtion nd other biologicl chnges tking plce in the fruit (Rthore et l., 2007). Rte of weight loss in both bgged nd control fruits ws not significntly different up to 6 DAH, but significntly higher (p<0.05) losses were observed in control fruits therefter. Unbgged fruits hd shriveled by 9 DAH (Plte 6) s opposed to 15 DAH for bgged fruits, indicting higher wter loss in control fruits. Cuticle covers fruits surfce nd one of its functions is to restrict trnspirtion wter loss. Bgged nd unbgged fruits my hve hd different cuticle structures (Amrnte et l., 2002) tht could hve led to differences in trnspirtion wter loss. Unbgged fruits with low nturl gloss nd irregulr lyer of lignified epiderml cells hve higher skin permebility to gses (Amrnte nd Bnks, 2002). However, no difference in skin permebility to wter, nd therefore weight loss, ws observed between bgged nd unbgged pers during four weeks of cold storge (Amrnte et l., 2002). 90

111 25 20 Unbgged control Bgged control b % weight loss b b Dys fter hrvest Fig. 25: Chnges in percentge weight loss in bgged nd unbgged mngo fruits during posthrvest storge t 25±1 o C, RH 60±5%. The verticl brs represent SE of the men of 9 replictes. When bsent, the SE fll within the dimensions of the symbol. denotes period of no significnt difference while b is period of significnt difference between bgged nd control fruits. (A) (B) Plte 6: Visible effects of trnspirtion wter loss on bgged (A) nd unbgged (B) mngo fruits t 9 DAH. 91

112 Fruit respirtion nd ethylene production rtes Fruit respirtion rte incresed with storge time up to the climcteric pek t 12 DAH in ll the tretments (Fig. 26 A) wheres ethylene production ws detected 9 DAH only, nd ssumed to be the pek ethylene production (Fig. 26 B). The increse in respirtion rte exhibited true climcteric pttern. In typicl climcteric fruit, low respirtion rte is observed before the onset of ripening, nd then surge in respirtory ctivity (Azzolini et l., 2005). This pek my correspond, precede or proceed optimum eting ripeness (Tucker, 1993). Optimum eting ripeness preceded respirtory climcteric nd pek ethylene production in Apple mngo fruit in this study. This indictes tht once strted, ripening ssocited chnges in Apple mngo my require very low ethylene levels tht were not detectble in this study. Smll mount of ethylene present in mngo fruit t hrvest is sufficient to initite ripening (Mitr nd Bldwin, 1997). Ripening mngo fruit hs low level of climcteric pek (3 μl/l) of internl ethylene (Tucker, 1993). Bender et l. (1995) reported mximum levels of bout 800 nl C 2 H 4 in ripe Tommy Atkins mngo fruit stored in ir t 20 o C. Tommy Atkins mngo fruit hd ethylene detected only once during storge, though respirtory pek preceded pek ethylene production (Mdigu, 2007). Pek ethylene production in mngo fruit cn occur before or fter the climcteric pek (Mitr nd Bldwin, 1997). This could be due to vrietl differences. 92

113 Respirtion rte (ml CO 2/Kg/h) c Unbgged control Unbgged 1-MCP Bgged control Bgged 1-MCP c c Dys fter hrvest bc bd (A) c (B) Ethylene production (nl/kg/h) Unbgged control Unbgged 1-MCP Bgged control Bgged 1- MCP Fig. 26: Respirtion rte (A) nd pek ethylene production (B) of both bgged nd unbgged mngo fruits, ech with nd without with 1-MCP tretment during posthrvest storge t 25± o C, RH 60±5%. The verticl brs represent SE of the men of six replictes. When bsent, the SE fll within the dimensions of the symbol. nd c denotes period of no significnt difference for bgging nd 1-MCP tretments respectively. b nd d denotes period of significnt difference for bgging nd 1-MCP tretments respectively. 93

114 The ptterns of respirtion nd ethylene production, nd consequently ripening behviour of mngo fruit vry mong vrieties, climtic conditions nd hrvesting dte (Mitr nd Bldwin, 1997). Lte hrvested mngo fruits do not hve pre-climcteric phse (Mitr nd Bldwin, 1997). This my hve occurred in this study s the fruits were hrvested t 168 DAB when ripening processes like loss of firmness, yellowing of the pulp nd strch degrdtion hd lredy commenced. Lte hrvested fruits hve higher numbers (Trewvs, 1982) nd more sensitive (Bron nd Jcomino, 2006) ethylene receptors. It seemed tht bsl level of ethylene nd respirtory ctivity ws sufficient to stimulte biochemicl chnges ssocited with mngo fruit ripening. Bgging hd significnt effect on fruit respirtion rte only t 9 nd 12 (respirtory pek) DAH. This could hve been due to more stress s consequence of higher trnspirtion wter loss during the period. Increse in respirtion rtes during ripening of climcteric fruits is considered to be homeosttic response of the mitochondri cused by detrimentl physicl nd chemicl chnges during ripening (Romni, 1984). Bgged mngo fruit hd reduced respirtion rte probbly due to lower O 2 nd higher CO 2 internl prtil pressure s reported in bgged pers (Amrnte et l., 2002), lthough, in their cse respirtion rte ws not ffected. Tretment with 1-MCP hd no significnt (p>0.05) effect on respirtion nd ethylene production rtes, though control unbgged fruits hd higher 94

115 respirtion nd ethylene peks of ml CO 2 /Kg/h nd nl/kg/h, respectively. However, dely of on-set time nd rtes of respirtion nd ethylene production by 1-MCP hs been reported for most of climcteric fruits. These include; bnns (Lohni et l., 2004), vocdo (Hershkovitz et l., 2005), tomtoes (Mostofi et l., 2003), strwberries (Bower et l., 2002), guv (Azzolini et l., 2005) nd pples (DeEll et l., 2001). Limited effect of 1-MCP on physico-chemicl chnges during ripening my hve been due to lte hrvesting when the ripening process hd lredy commenced. Yellowing of the fruit pulp nd brekdown of strch nd chlorophyll of Apple mngo in this study hd been initited by the time of hrvest, 168 DAB. Lte hrvested Kent mngo fruit ws too ripe to respond to the 1-MCP tretment (Plotto et l., 2003). A single dose of 1-MCP tretment of pech fruit hd little effect on ethylene biosynthesis, but multiple tretment delyed significntly the induction of ethylene biosynthesis (Mthooko et l., 2001). Limited fruit response to single tretment with 1-MCP with respect to ethylene biosynthesis could hve been due to ethylene receptor sites generted within short time (Mthooko et l., 2001). Tretment of strwberry fruits with 1.0 µl 1-MCP hd little effect on fruits stored in ir, though it protected the fruits from effect of externl ethylene (Bower et l., 2002). The decrese in respirtion rtes during post-climcteric represents the loss of homeosttic bility of mitochondri, with the predominnce of senescence during this period (Azzolini et l., 2005). 95

116 4.2.4 Fruit sensory qulity on ripening Bgged nd unbgged fruits were fully ripe (peel completely turned yellow nd pulp ttined eting softness) t 7 DAH (Plte 7). Bgged fruits were rted superior in terms of generl ppernce, pulp nd peel colour, nd overll cceptnce (Fig. 27). This could be ttributed to bgged fruits being brighter s indicted by higher L vlues nd lck of blemishes. The differences in rom, tste nd texture between bgged nd unbgged fruits were not significnt (p>0.05) though bgged fruits hd higher scores Thus, there ws no significnt difference (p>0.05) between bgged nd unbgged fruits in terms of eting qulity. It is the sugrs/cids rtio tht determines mngo fruit eting qulity (Rthore et l., 2007). Indeed, there were no significnt differences (p>0.05) in TSS nd TTA contents between bgged nd unbgged fruits during storge. Totl soluble solids nd totl titrtble cidity, nd hence eting qulity of Keitt mngo fruit ws lso not ffected by bgging (Hofmn, 1997). Improved overll cceptnce of bgged fruits could, therefore, be ttributed to better visul ppernce nd not eting qulity. 96

117 (A) (B) (C) (D) Plte 7: Unbgged (A) nd bgged (B) peel, nd unbgged (C) nd bgged (D) pulp ppernce of mngo fruit on ripening, 7 DAH (Storge: 25±1 o C, RH 60±5%). 97

118 4.5 Unbgged fruits 4 Bgged fruits 3.5 Score (9-point hedonic scle) b b b b Generl ppernce Peel colour Pulp colour Texture Arom Tste Overll cceptnce Sensory ttribute Fig. 27: Sensory qulity scores of bgged nd unbgged mngo fruits on full ripening, seven DAH. Rting ws done on 9-point hedonic scle (1-like extremely nd 9-dislike extremely). The verticl brs represent SE of the men of 15 replictes. denotes period of no significnt difference while b is period of significnt difference between bgged nd control fruits. 98

119 CHAPTER FIVE 5.0 CONCLUSION AND RECOMMENDATIONS The min purpose of fruit bgging is to prevent mechnicl dmge nd, physiologicl nd pthologicl disorders. This study showed tht bgging controlled development of rust lesions on Apple mngo fruit peel, nd lso improved the posthrvest shelflife by six dys. In ddition, bgging did not ffect the eting qulity of the fruit, but improved visul ppernce nd cceptnce. Therefore, prehrvest bgging cn be pplied for production of high qulity Apple mngo fruits for export mrket. Posthrvest 1-MCP (20 ppm) tretment did not retrd ripening of Apple mngo fruit hrvested t 168 DAB. In ddtion, its effect on chnges in fruit qulity prmeters during ripening ws miniml. Cold storge of mngo fruit is highly limited by its susceptibility to chilling injury, nd filure by 1-MCP to slow Apple mngo ripening presents nother big setbck in the ttempt of improving its posthrvest shelflife. However, retrded loss of firmness by 1-MCP tretment, though for short durtion, could be useful in minimizing mechnicl dmge during loding nd shipping. Prehrvest bgging is however lborious, though sfe nd esy to pply. The vibility of its ppliction will depend on frm lbour, which is chep nd vilble in Keny. However, its economic vibility in Keny should be scertined by investigtions on cost-benefit nlysis nd prcticbility. Stkeholders in fruits industry should link with pper mnufcturing industry so s to come up with suitble bgging mterils nd user friendly bgs for 99

120 vrious fruits. Moreover, impct of prehrvest bgging on fruit qulity my be ffected by durtion of bgging nd climtic conditions. More studies should be done on these two fctors so s to find out the optimum bgging period for mximum results. Investigtions on light penetrting bgging mterils or unbgging the bgged fruits prior to hrvest should be done s n ttempt to mitigting the negtive impct of bgging on the chrcteristic fruit peel colourtion. The obvious benefits tht cn be ccrued from successful use of 1-MCP on mngo fruit wrrnts further investigtions on fctors such s mturity stge nd mode of ppliction s these my hve n effect on fruit response. Therefore, investigtions on the effect of different mturity stges without significntly compromising on fruit eting qulity) nd intermittent 1- MCP ppliction during posthrvest period on mngo fruit response should be done. 100

121 REFERENCES Ahenkor, K., Kyei., M.A., Mrfo, E.K. nd Bnful, B Nutritionl composition of flse horn Apntu p plntin during ripening nd processing. Africn Crop Science Journl, 2: Albrigo, L. G. nd Anchor, D.S Ultrstructurl development nd other chrcteristics of stylr-end russeting of Nvel ornges in Florid. Proceedings of Florid Stte Horticulturl Society, 115: Amrnte, C. nd Bnks, N.H Ripening behviour, posthrvest qulity nd physiologicl disorders of coted pers (Pyrus communis). New Zelnd Journl of Crop nd Horticulturl Science, 30: Amrnte, C., Bnks, N.H. nd Mx, S Effects of prehrvest bgging on fruit qulity nd posthrvest physiology of pers (Prunus communis). New Zelnd Journl of crop nd Horticulturl Science, 30: Amrnte, C., Bnks, N.H. nd Mx, S. 2002b. Prehrvest bgging improves pckout nd fruit qulity of pers (Pyrus communis). New Zelnd Journl of crop nd Horticulturl Science, 30: Ann, P.J., Lu, L.S., Chung, T.Y. nd Ko, C.W Effect of fruit bgging nd mulching on control of mngo fruit nthrcnose disese. Plnt Pthology Bulletin, 7: AOAC (Assocition of Officil Anlyticl Chemists) Officil Methods of Anlysis., Wshington. D.C. Arnon, D Copper enzymes in isolted chloroplsts: Polyphenoloxidse in Bet vulgris. Plnt Physiology, 24:

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132 Mitr, S.K. nd Bldwin, E.A Mngo. In: Mitr, S.K. (ed). Posthrvest Physiology nd Storge of Tropicl nd Subtropicl Fruits. CAB Interntionl, New York, pp Mostofi, Y., Toivonen, P.M.A., Lessni, H., Bblr, M. nd Lu, C Effects of 1-methylcyclopropene on ripening greenhouse tomtoes t three storge tempertures. Posthrvest Biology nd Technology, 27: Mtebe, K., Mmiro, P. nd Fwej, L Sensory ttributes, microbil qulity nd rom profiles of off vine ripened mngo (Mngifer indic L.) fruit. Africn journl of biotechnology, 5: Ngy, S Vitmin C content of citrus fruits nd their products: review. Journl of Agriculture nd Food Chemistry, 28: Nymbo, B., Vrel, A.M. nd Seif, A.A A modified Frmer Field School on Integrted Pest Mngement of Mngo Production in Smllholder Systems in Keny. ICIPE (Interntionl Centre of Insect Physiology nd Ecology), pp1-25. Pelyo, C., Ebeler, S.E. nd Kder, A.A Posthrvest life nd flvour qulity of three strwberry cultivrs kept t 5 o C in ir or ir + 20 kp CO 2. Posthrvest Biology nd Technology, 27: Petti, D., Gonzlez, A., Gonzlez, G., Sotelo, R. nd Bez-Snudo, R Ultrstructure nd permebility of cuticle during the ontogeny of fruits mngos (Mngifer indic L.). (Accessed on 5/7/2008). 112

133 Plotto, A., Bi, J., Bldwin, A. nd Brecht, J.K Effect of pretretment of intct Kent nd Tommy Atkins mngoes with ethnol vpour, het, or 1-methylcyclopropene on qulity nd shelf-life of fresh-cut slices. Proceedings of Florid Stte Horticulturl Society, 116: Qiuping, Z., Wenshui, X. nd Jing, Y Effects of 1- Methylcyclopropene Tretments on Ripening nd Qulity of Hrvested Spodill Fruit. Posthrvest Biology nd Technology, 44: Rthore, H.A., Msud, T., Smmi, S. nd Soomro, H.A Effects of storge on physico-chemicl composition nd sensory properties of mngo (Mngifer indic L.) vr. Dosehri. Pkistn Journl of Nutrition, 6: Rodriguez-Amy, D.B Chnges in crotenoids during processing nd storge of foods, Pudmed, 49: Romni R.J Respirtion, ethylene, senescence, nd homeostsis in n integrted view of posthrvest life. Cndin Journl of Botny, 62: Slisbury, F. B. nd Ross, C. W Plnt physiology. Wdsworth Publishing Co., Cliforni. Sne, V.A., Choursi, A. nd Nth, P Softening in mngo (Mngifer indic cv. Dshehri) is correlted with the expression of n erly ethylene response, ripening relted expnsin gene, MiExpA1. Posthrvest Biology nd Technology, 38:

134 Srnwong, S., Sornsrivichi, J. nd Kwno, S Performnce of portble NIR instrument for Brix vlue determintion of intct mngo fruit. Journl of Ner Infrred Spectroscopy, 11: Shirtke, K. nd Mrtinoi, E Trnsporters in fruit vcuoles. Plnt Biotechnology, 24: Signes, A.J., Burlo, F., Mrtinez-Snchez nd Crbonell-Brrchin effects of prehrvest bgging on qulity on qulity of blck tble grpes. World Journl of Agriculturl Sciences, 3: Sisler, E.C. nd Serek, M Inhibitors of ethylene responses in plnts t the receptor level: recent developments. Physiology of Plnts, 100: Tmjind, B., Siriphrich, J., Nobuchi, T Antomy of lenticels nd the occurrence of their discolourtion in mngo (Mngifer indic cv. Nmdokmi). Ksetsrt, J. (Nt. Sci. Suppl.), 26: Trewvs, A.J Growth substnce sensitivity; the limiting fctor in plnt development. Physiology of plnts, 55: Tucker, G.A Introduction. In: Seymour, G. B., Tylor, J. E. nd Tucker, G. A. (eds). Biochemistry of fruit ripening. Chpmn nd Hll, London, pp Tys, J. A., Hofmn, P. J., Underhill, S. J. R. nd Bell, K.L Fruit cnopy position nd pnicle bgging ffects yield nd qulity of Ti So lychee. Scienti Horticulture, 72: Ued, M., Sski, K., Utsunomiy, N. nd Shimbyshi, Y Chnges in properties during mturtion nd ripening of Chiin Hwng No

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137 APPENDICES Appendix I: Tomtoes untreted (A) nd treted (B) with 1-MCP (20 ppm) 7 dys fter hrvest (DAH) A B 117

138 Appendix II: Sensory evlution form Sheet No Dte:.. Pnelist nme: Phone number.. Test the provided two smples either by tsting or visully, nd using the 9- point hedonic scle provided, indicte the score of the stted ttribute. 9-point hedonic scle 1. Like extremely 6. Dislike slightly 2. Like very much 7. Dislike modertely 3. Like modertely 8. Dislike very much 4. Like slightly 9. Dislike extremely 5. Neither like nor dislike Smple code At hrvest Peel ppernce 2. Peel colour 3. Overll cceptnce On ripening 1. Generl ppernce 2. Peel colour 3. Pulp colour 4. Texture 5. Arom 6. Tste 7. Overll cceptnce Comments: 118

139 Appendix III: The Hunter s CIE (Commission Interntionle de l Eclirge) L* * b* system colour spce. The Hunter L* (whiteness/drkness), * (redness/greenness) nd b* (yellowness/blueness) CIE (Commission Interntionle de l Eclirge) system colour spce. Hue describes visul senstion ccording to which n re ppers to be similr to one or proportions of two of the perceived colours, red, yellow, green nd blue. The hue ngle is thus the ctul colour. An ngle of 0 C = red-purple hue, 90 C =yellow hue, 180 C= bluish green, 270 C=blue. Totl colour chnge mesures the chnges in the three colour components: Lightness L*, red-green * nd yellow-blue b*. On horizontl xis, positive * indictes hue of red-purple, negtive * indictes bluish green, positive b* indictes yellow nd negtive b* indictes blue. 119