Posthrvest Biology nd Tehnology 31 (24) 127 136 Intertions etween 1-MCP onentrtion, tretment intervl nd storge time for Brtlett pers J.H. Ekmn, M. Clyton 1, W.V. Bisi, E.J. Mithm Deprtment of Pomology, University of Cliforni, Dvis, CA 95616-8683, USA Reeived 4 June 22; epted 18 July 23 Astrt Storge trils were rried out over two sesons to determine suitle tretment protool for the use 1-methylylopropene (1-MCP) with Brtlett (Willims) pers. In the 2 seson, pers were exposed to,.1,.1,.5 or 1. ll 1 1-MCP t C, then stored t 1 C for up to 24 weeks efore ripening t 2 C. The effets of the lower onentrtions dissipted fter time, llowing fruit to reh eting ripeness. Superfiil sld development ws delyed, ut not prevented, in these fruit. Although 1. ll 1 effetively prevented sld, these fruit filed to soften. Overll, onentrtions of.1.5 ll 1 1-MCP ppered to hve the most potentil s storge tretments. In the 21 seson, fruit were exposed to,.2 or.4 ll 1 1-MCP t C. After 4 or 6 weeks t 1 C, hlf the fruit were re-treted t C nd stored t 1 C for further 4 or 6 weeks. Re-tretment fter 4 weeks hd greter effet on olor development nd softening fter storge thn did the initil 1-MCP pplition. In ontrst, fruit re-treted fter 6 weeks showed little response to the dditionl 1-MCP exposure. These results suggest tht green fruit reover ethylene sensitivity more slowly when re-treted with 1-MCP fter period of storge. However, if fruit hve strted to ripen they re reltively insensitive to dditionl 1-MCP. Tretment with 1-MCP redued fruit sensitivity to hndling dmge, even fter ripening. The results re disussed in terms of the prtil diffiulties with pplition of 1-MCP to Brtlett pers s well s potentil ommeril enefits. 23 Elsevier B.V. All rights reserved. Keywords: 1-Methylylopropene; Ethylene inhiitor; Europen pers; Internl rekdown; Ripening; Superfiil sld 1. Introdution Storge of Brtlett pers is typilly limited to 2 3 months in ir, even under idel storge onditions t Corresponding uthor. Present ddress: NSW Deprtment of Agriulture, Loked Bg 26, Gosford, NSW 225, Austrli. Tel.: +61-2-4348-19; fx: +61-2-4348-191. E-mil ddress: jenny.ekmn@gri.nsw.gov.u (J.H. Ekmn). 1 Present ddress: Deprtment of Pestiide Regultion, 1 I Street, Srmento, CA 95812, USA. 1 C. In most ses, the end of storge life is due to the onset of physiologil disorders, prtiulrly superfiil sld nd ore rekdown. Ethylene produed y the fruit n exerte these disorders, s well s use premture yellowing nd softening during storge. Lte hrvested fruit re prtiulrly suseptile to these disorders, whih my egin to pper within month of hrvest (Ju et l., 21). Methods used to extend the storge life of pers inlude tretment with ethoxyquin, fruit otings, nd low oxygen tmospheres. There re some 925-5214/$ see front mtter 23 Elsevier B.V. All rights reserved. doi:1.116/j.posthrvio.23.7.2
128 J.H. Ekmn et l. / Posthrvest Biology nd Tehnology 31 (24) 127 136 environmentl onerns with the use of ethoxyquin nd it is not registered for use on pers in Cliforni. While fruit otings hve een found to redue rtes of ripening nd sld development, they n result in uneven ripening nd lothy olor development (Meheriuk nd Lu, 1988). Storing pers in 1 1.5% O 2 n effetively redue the rte of ripening nd the inidene of physiologil disorders, therey extending storge life (Yoshid et l., 1986; Kder, 1989). However, umultion of CO 2 n inrese internl rowning, with suseptile fruit unle to tolerte >1% CO 2 during storge (Clypool, 1973). An lterntive method of slowing ripening is tretment with n inhiitor of ethylene tion. One suh ompound, 1 methylylopropene (1-MCP), is now registered for use on pples in the US, with pplitions pending for wider use on other fruit nd vegetles (Agrofresh, USA). 1-MCP is thought to t y inding irreversily to ethylene reeptors in the fruit, therey preventing the effets of ethylene in the plnt tissues (Sisler nd Serek, 1997). Exposure to 1-MCP n inhiit ripening of limteri fruit suh s pples, vodos, nns, kiwifruit, stonefruit nd mngos (Wtkins nd Miller, 23). Furthermore, treting pples with 1-MCP n redue the inidene of superfiil sld nd other physiologil disorders (Fn nd Mttheis, 1999; Wtkins et l., 2). Pers hve een shown to respond to 1-MCP, typil effets inlude delys in degreening nd softening nd redued respirtion nd ethylene prodution (DeWild et l., 1999; Britelle et l., 21). It seemed possile tht 1-MCP ould lso redue superfiil sld on pers. Unlike pples, Brtlett pers only reh full dessert qulity when they soften. As the effets of 1-MCP re not redily reversile y exposure to ethylene, tretments must e pplied in suh wy tht the fruit ripen normlly fter period of storge. The rte t whih fruit regins ethylene sensitivity is primrily dependent on the onentrtion of 1-MCP pplied nd the durtion of storge (Wtkins et l., 2). We onduted series of experiments during 2 nd 21 exmining the effets of different onentrtions of 1-MCP with different storge durtions. In the first experiment, Brtlett pers were exposed to 1 ll 1 of 1-MCP. From this work, we determined tht onentrtions etween.1 nd.5 ll 1 were likely to e the most suitle for per fruit, s pers ripened within resonle time fter removl from storge. However, suh low onentrtions re likely to lose their effetiveness within reltively short period. It ould e possile to extend the effets of 1-MCP s well s improve mrketing flexiility y pplying the gs more thn one during storge. Therefore, the seond seson s experimentl work used onentrtions of.2 nd.4 ll 1 1-MCP, nd repeted these pplitions fter 4 or 6 weeks of old storge. The results re disussed in terms of the potentil to implement ommeril tretment of 1-MCP for Brtlett per fruit. 2. Mterils nd methods 2.1. Fruit mteril Pers were hrvested from ommeril orhrd in the Srmento re on 2 August 2 nd 18 July 21. In the initil experiment, hrvested fruit were divided into six replite groups for tretment. The seond set of experiments used three replite groups omprising pers seleted from different hrvest ins. In oth sesons, the hrvested fruit were trnsported to UCDvis y ir-onditioned vehile. After sorting to otin undmged fruit of uniform size nd olor, the pers were ooled overnight to C. 2.2. Tretments The pers were pled into steel tnks for tretment. A smll eletri fn ws lso pled inside eh tnk to ensure even distriution of the 1-MCP gs round the fruit. The tnk lids were onstruted so s to fit into wter filled troughs, forming hermeti sel. Wrm wter ws injeted into seled flsk ontining mesured mount of the Ethyllo powder (.14%.i., Florlife In., Wlteroro, SC, USA) to generte 1-MCP gs. By ontinuing to injet wter until the flsk ws full, the gs ws fored out of the flsk nd into the tnk. The first set of experiments exmined the effets of different 1-MCP onentrtions on qulity nd ripening of pers fter vrious periods of old storge. Fruit were treted with,.1,.1,.5 or 1. ll 1 1-MCP for 12 h t C. Immeditely fter tretment, 18 fruit from eh group were exposed to 1 ll 1 ethylene for 42 h then pled t 2 C for up to 19 dys. The
J.H. Ekmn et l. / Posthrvest Biology nd Tehnology 31 (24) 127 136 129 remining fruit were stored t 1 C for 6, 12, 18 or 24 weeks efore ripening t 2 C for t lest 8 dys. The seond set of experiments used only low 1-MCP onentrtions, ut repeted the pplitions. Fruit ssigned to oth the 4 nd 6 week tretment shedules were given n initil exposure to,.2 or.4 ll 1 1-MCP for 12 h t C. Ten dditionl fruit from eh replition were ssessed immeditely fter tretment, with further 1 ssessed fter 1 week t 2 C. After either 4 or 6 weeks t 1 C, we removed hlf of the fruit from the pproprite shedule for ssessment. Mesurements were tken immeditely or following 1 week of ripening t 2 C. The remining fruit were re-treted with the sme 1-MCP onentrtion s hd een used previously (,.2 or.4 ll 1 ) for 12 h t C. The re-treted fruit were evluted fter seond storge period of the sme durtion s eh group hd lredy ompleted (4 or 6 weeks), oth efore nd fter 1 week of ripening t 2 C. 2.3. Qulity ssessment During initil experiments, we reorded per ttriutes on removl from old storge nd then every 2 dys during susequent ripening t 2 C. At eh ssessment, three fruit were destrutively evluted from eh of the six replite groups. Fruit in the seond set of experiments were ssessed on removl from storge nd gin fter week t 2 C. In this se, eh ssessment used 1 fruit from eh of three replite groups. 2.3.1. Color Skin olor ws mesured using Minolt Chrom Meter (Model CR3, Minolt Co., Jpn) in the L mode under stndrd CIE illuminnt C. Mesurements were tken on opposite sides of eh fruit, nd the men vlue lulted. Color hnges from green to yellow were indited y lulting the hue ngle (H ), from tn 1 /. 2.3.2. Flesh firmness Firmness ws mesured using n Ametek penetrometer (Ametek In., Htfield, PA USA) mounted in drill press stnd nd fitted with n 8 mm proe. Setions of per skin were removed t the equtor on either side of the fruit to llow two seprte redings of eh per. 2.3.3. Disorders We evluted the pers for inidene nd severity of sld, dey nd internl rekdown. Sld, dey nd internl rekdown were rnked sujetively s : none; 1: slight; 2: moderte; or 3: severe, nd the perentge of the fruit tht were ffeted ws lulted. In the se of sld, the perentge of eh fruit s surfe tht ws ffeted ( 1%) ws visully estimted. 2.4. Gs exhnge Mesurements of respirtion rte nd ethylene prodution were mde in oth sesons using three replite groups of six fruit per tretment. The fruit were seled into 3.75 l glss jrs, llowing CO 2 to umulte to.1.3%. This took from 1 min to 3 h, depending on the ripeness stge nd temperture. Conentrtions of CO 2 nd ethylene in the hedspe of eh jr were determined y rpid gs nlysis (VIA51, Hori, Jpn) or gs hromtogrphy (Model AGC Series 4, Hh-Crle Co., USA). In the first experiment, we lulted the rtes of CO 2 nd ethylene evolution dily for t lest 8 dys during ripening t 2 C. The following seson, mesurements were mde weekly while fruit were stored t 1 C. 2.5. Dt nlysis Chnges in olor nd firmness in the initil experiments were plotted s sigmoidl urves nd the numer of dys t 2 C efore eh ttriute rehed predetermined limit ws lulted (Sigm Plot sientifi softwre, Version 4, SPSS In., IL, USA). The limits used were H = 12 nd firmness = 18 N, s these vlues indited tht fruit were essentilly yellow nd fully softened, respetively. The numer of dys tken for fruit to reh these limits ws sujeted to nlysis of vrine (ANOVA). Dt ws nlyzed y time s well s y tretment. The perentge of the fruit tht were ffeted y sld nd/or internl rekdown ws lulted sed on dt from dy 8 of ripening only. The severity sores for oth disorders nd the perentge of the surfe re of eh fruit tht ws sld ffeted were ompred nd nlyzed y ANOVA. In the seond set of experiments, dt ws nlyzed y ANOVA ording to time of storge nd
13 J.H. Ekmn et l. / Posthrvest Biology nd Tehnology 31 (24) 127 136 tretment, nd ll time/tretment omintions were ompred. All ANOVAs were performed using SAS sttistil softwre (Version 7, SAS Institute In., USA) to ondut series of ftoril nlyses. Mens were seprted using the Student Newmn Keuls test to lulte the lest signifint differene. 3. Results 3.1. 1-MCP onentrtion nd storge time 3.1.1. Color nd firmness Applition of 1-MCP hd no effet on olor development during storge t 1 C. Untreted fruit were softer thn pers treted with.5 or 1. ll 1 1-MCP, ut this differene ws only pprent fter 24 weeks storge t 1 C (dt not shown). In ontrst, lrge differenes in olor nd firmness ourred during ripening t 2 C. As the fruit were mesured t 2 dy intervls, it ws possile to generte reltively ontinuous reltionship etween fruit ttriutes nd time. An exmple is shown in Fig. 1. Both mgnitude nd durtion of the effets of 1-MCP were relted to tretment onentrtion (Tle 1). Tretment with.1 ll 1 1-MCP did not ffet the rte of olor development or softening of per fruit. However, inresing the 1-MCP onentrtion hd progressively greter effets on softening nd yellowing, nd for longer periods. None of the fruit treted with 1. ll 1 1-MCP nd stored for up to 18 weeks t C fully softened to 18 N within 14 dys t 2 C(Tle 1). A numer Firmness (N) 8 6 4 2 Control.1µL L -1.1µL L -1.5µL L -1 1.µL L -1 2 4 6 8 1 12 Dys t 2 C Fig. 1. Chnges in firmness of pers during ripening t 2 C. Fruit were treted with,.1,.1,.5 or 1. ll 1 1-MCP nd stored for 6 weeks t 1 C efore ripening. Error rs indite the stndrd devition of eh men vlue (n = 6). of fruit treted with1. ll 1 1-MCP softened to ner 18 N when storge time ws inresed to 24 weeks t 1 C; however, others remined firm nd therefore the men vlue (33 N) remined greter thn the 18 N ripeness threshold. As the time in storge t 1 C inresed, olor development preeded softening to greter extent. Yellow olor development nd softening were synhronized when fruit were ripened immeditely fter hrvest. In ontrst, pers kept t 1 C for 18 or 24 weeks yellowed fully during storge yet still required 5 6 dys t 2 C to soften (Tle 1). Loss of synhroniztion in ripening prmeters ws gretest in the 1-MCP treted fruit, ut lso ourred in untreted ontrol fruit. The effet ws gretest in the Tle 1 Dys t 2 C to soften (men firmness = 18 N) nd for skin olor to eome yellow (men H = 12) for pers treted with 1-MCP t C then stored for up to 24 weeks t 1 C efore ripening t 2 C 1-MCP ( ll 1 ) Firmness (weeks) Color (weeks) 6 12 18 24 6 12 18 24 4.9 B 4. A 4.2 A 5.1 B 6.2 C 5.2 D 3.4 C 2.4 B.5 A A.1 4.8 A 4.2 A 4.1 A 6.4 C 5.9 B 5.2 D 3.6 C 2.1 B A A.1 5.9 B 4.4 A 4.3 A 6.6 B 6. B 6. D 3.8 C 1.9 B.4 A A.5 13.8 C 8.6 B 7.5 B 5.2 A 4.9 A 9.4 D 5.7 C 3. B.1 A A 1. >14. da >14. A >14. A >14. A >14. A 11.7 dd 8.6 C 5.1 B A A Vlues re mens from six replite groups lulted using sigmoidl regression of dt olleted t 2 dy intervls during ripening. Different letters indite signifint (P =.5) differenes etween tretment ( d) or etween evlution times (A D). Fruit treted with 1 ll 1 ethylene for 24 h prior to ripening t 2 C.
J.H. Ekmn et l. / Posthrvest Biology nd Tehnology 31 (24) 127 136 131 pers treted with 1. ll 1 1-MCP nd stored for 18 weeks, whih were yellow when trnsferred from 1 to 2 C yet remined hrd nd inedile. In this se, storge life ws ended not y softening, ut y disese. In generl, the time tken for fruit to soften fter trnsfer to 2 C deresed with length of storge t 1 C. However, when pers were stored for more thn 12 weeks, this ws reversed. On verge, fruit treted with,.1 or.1 ll 1 1-MCP took t lest 2 dys more to reh edile softness when they hd een stored for 18 weeks ompred to 12 weeks (Tle 1). However, this loss of pity to soften (P <.1) ws not found in fruit treted with.5 ll 1 1-MCP. In this se, the time tken for fruit to reh edile softness deresed signifintly etween 12 nd 18 weeks (P <.1), nd ws still deresing t the end of the experimentl period. 3.1.2. Physiologil disorders Tretment with 1-MCP redued the inidene nd severity of superfiil sld. All pers stored for 6 weeks remined free of sld fter ripening (Fig. 2). However, the inidene nd severity of sld in fruit treted with or.1 ll 1 1-MCP inresed onsiderly with storge time. After 24 weeks, symptoms of sld were lredy evident when the fruit were removed from storge. Tretment with.1 ll 1 1-MCP redued sld severity on ripe fruits for up to 18 weeks (P <.1) (dt not shown), ut hd less effet on sld inidene. Exposure to.5 ll 1 1-MCP redued oth sld severity nd numer of fruit ffeted (P <.1), while fruit treted with 1. ll 1 1-MCP remined free of sld for the durtion of the experiment. 1-MCP tretment lso redued internl rekdown (Fig. 2). After 18 weeks storge, internl rekdown ourred more frequently in the ontrols thn in pers treted with.1 ll 1 1-MCP, nd more frequently in these fruit ompred to pers treted with higher 1-MCP onentrtions (P <.1). After 24 weeks storge nd 8 dys t 2 C, 5% of the fruit treted with.5 ll 1 1-MCP hd symptoms of internl rekdown, nd the men grde ws 1: slight. However, internl rekdown ws more severe in fruit treted with lower 1-MCP onentrtions (P <.1), eing 2: moderte to 3: severe. No internl rekdown ws found in ny of the pers exposed to 1. ll 1 1-MCP. Sld (%) Internl Brekdown (%) 1 8 6 4 2 8 6 4 2 () () ontrol.1µl L -1.1µL L -1.5µL L -1 1.µL L -1 5 1 15 2 25 Weeks Stored t -1 o C (+ 8d t 2 C) Fig. 2. Perentge of fruit with superfiil sld () nd internl rekdown () following tretment with,.1,.1,.5 or 1. ll 1 1-MCP nd storge t 1 C for up to 24 weeks followed y 8 dys of ripening t 2 C. Error rs indite the stndrd devition of eh men (n = 6). 3.1.3. Gs exhnge The degree nd durtion of the effets of 1-MCP on CO 2 nd ethylene prodution t 2 C were relted to the tretment onentrtion (Fig. 3 nd ). Ethylene prodution during ripening ws inhiited y exposure to.1 ll 1 1-MCP ompred to untreted fruit when fruit were stored for 6 weeks t 1 C(P<.1), ut not when the fruit ws stored for longer periods. Similrly, tretment with.5 or 1. ll 1 1-MCP redued CO 2 nd ethylene prodution y ripening fruit stored for, 6 or 12 weeks (P <.1). However, fter 18 weeks of storge, men ethylene prodution ws no longer ffeted y 1-MCP pplition, nd only fruit treted with 1. ll 1 1-MCP respired more slowly thn the untreted ontrols during ripening. Interestingly, fruit treted with.5 ll 1 1-MCP nd stored for 24 weeks respired fster thn fruit from other tretments (P =.4), lthough ethylene prodution ws less ffeted (P =.2484).
132 J.H. Ekmn et l. / Posthrvest Biology nd Tehnology 31 (24) 127 136 CO 2 Prodution (mmol kg -1 h -1 ) 3. 2.5 2. 1.5 1. () The initil rte of ethylene prodution, mesured when the fruit were first removed from storge, inresed with storge time t 1 C(P<.1). For exmple, ethylene prodution y ontrol fruit stored for, 6, 12, 18 nd 24 weeks ws 3.5 1 5,.8,.16,.26 nd.33 lkg 1 h 1. These inreses in initil mesurements t 2 C were oserved for ll tretments. Ethylene Prodution (nmol kg -1 h -1 ).5. 5 4 3 2 1 () 6 12 18 24 Storge Time (weeks t 1 C) Fig. 3. Men rtes of CO 2 () nd ethylene () prodution during ripening t 2 C following tretment with,.1,.1,.5, or 1. ll 1 1-MCP nd storge for up to 24 weeks t 1 C. Error rs indite the stndrd devition of eh men (n = 3). When dt from ll the storge times were onsidered, tretment with.5 or 1. ll 1 1-MCP redued men CO 2 prodution ompred to untreted fruit (P <.1). However, men ethylene prodution during ripening ws not redued y exposure to 1-MCP. Autotlyti ethylene prodution during ripening ws oserved only in fruit stored for or 6 weeks (dt not shown). Ethylene prodution y fruit treted with,.1 or.1 ll 1 of 1-MCP nd then immeditely ripened (with 42 h exposure to ethylene) inresed from ner to.5.8 lkg 1 h 1 during 8 dys t 2 C. Fruit treted with these sme 1-MCP onentrtions nd stored for 6 weeks underwent pproximtely douling of ethylene prodution during ripening. However, when fruit were stored for longer thn 6 weeks, their rte of ethylene evolution deresed during ripening t 2 C. This effet ws oserved in ll fruit, inluding those treted with the highest 1-MCP onentrtion. 3.2. Repeted 1-MCP pplition 3.2.1. Color nd firmness Results from fruit treted with.2 or.4 ll 1 1-MCP were intermedite etween results otined the previous seson for fruit treted with.1 or.5 ll 1 1-MCP fter the sme storge time. This indited tht fruit were onsistent etween sesons. Color nd firmness hnged from their vlues t hrvest during storge t 1 C. In prtiulr, ll fruit yellowed during storge t 1 C. Even 4 weeks fter hrvest, the men H vlues of stored fruit hd deresed from initil vlues of 115.1 113. (P <.1). Yellowing of stored fruit ontinued for the durtion of the experiment (Fig. 4), ll fruit stored for totl of 12 weeks eing yellower thn those removed from storge erlier (P <.1). Softening t 1 C ourred more slowly thn olor hnge. After derese (P <.1) of pproximtely 17.4 N etween weeks nd 6, fruit did not soften during storge t 1 C(Fig. 5). Overll, oth yellowing nd loss of firmness during storge t 1 C were unffeted y 1-MCP tretment for the onentrtions nd storge times used. However, signifint vritions were found mong the tretments when the fruit were ripened t 2 C. All of the 1-MCP treted fruit ripened fter 4 or 6 weeks t 1 C remined greener nd firmer thn the untreted ontrols (P <.1) (Figs. 4 nd 5). Exposure to.4 ll 1 hd more effet thn did.2 ll 1 1-MCP (P <.1). Pers treted with either onentrtion nd stored for 4 weeks t 1 C did not eome fully yellow or soft fter 6 dys of ripening. After 6 weeks storge, most of the fruit rehed eting ripeness fter the sme period t 2 C, lthough the.4 ll 1 treted fruit remined firmer thn idel for eting qulity (22 N). The timing of re-pplition of 1-MCP ffeted per olor nd firmness during susequent ripening. Yellow
J.H. Ekmn et l. / Posthrvest Biology nd Tehnology 31 (24) 127 136 133 115 11 15 Dy 1 8 6 Dy 1 4 Color (H o ) 95 9 115 11 15 1 95 9 ontrol.2µl L -1.4µL L -1 4 6 4+4 6+6 Storge Time (weeks t 1 C) 6 Dy Fig. 4. Color (H ) of pers treted with,.2 or.4 ll 1 1-MCP nd stored for 4 or 6 weeks t 1 C. Pers were either evluted t 4 or 6 weeks, or re-treted with the sme 1-MCP onentrtion s previously nd stored for n dditionl 4 or 6 weeks. Mesurements were tken immeditely fter removl from storge (Dy ) nd following 6 dys ripening t 2 C (Dy 6). Different letters indite signifint differenes etween the tretments t eh ssessment time. Color (H ) t hrvest ws 115.. Firmness (N) 2 8 6 4 2 ontrol.2µl L -1.4µL L -1 4 6 4+4 6+6 Storge Time (weeks) 6 Dy Fig. 5. Firmness (N) of pers treted with,.2 or.4 ll 1 1-MCP nd stored for 4 or 6 weeks t 1 C. Pers were either evluted t 4 or 6 weeks, or re-treted with the sme 1-MCP onentrtion s previously nd stored for n dditionl 4 or 6 weeks. Mesurements were tken immeditely fter removl from storge (Dy ) nd following 6 dys ripening t 2 C (Dy 6). Different letters indite signifint differenes etween the tretments t eh ssessment time. Firmness t hrvest ws 84.4 N. olor development nd softening were strongly inhiited when fruit were re-treted fter 4 weeks nd stored for further 4 weeks (4 + 4) (Figs. 4 nd 5). These fruit remined green nd hrd fter 6 dys t 2 C. However, pplition of 1-MCP hd less effet when re-tretment ws fter 6 weeks. These fruit eme fully yellow nd soft during the ripening period. Differenes in ripening hrteristis etween the two re-tretment times were highly signifint. For exmple, the fruit re-treted with.2 or.4 ll 1 1-MCP fter 4 weeks remined firmer fter totl of 8 weeks storge nd 6 dys ripening thn those treted one t hrvest nd ripened fter 4 weeks, even though the totl storge time ws douled (P <.1). In ontrst, firmness of fruit re-treted with 1-MCP fter 6 weeks then stored for n extr 6 weeks efore ripening ws not different from fruit treted one nd ripened fter 6 weeks. Control fruit softened nd yellowed more thn the fruit re-treted with 1-MCP in oth tretment shedules (P <.1). Fruit re-treted with.4 ll 1 1-MCP fter 4 weeks remined firmer during ripening thn those re-treted with.2 ll 1 1-MCP (P <.1), lthough olor development ws unffeted. 1-MCP onentrtion did not ffet hnges during ripening when the fruit were re-treted fter 6 weeks. All of these fruit ttined full yellow olor fter 6 dys of ripening. As in previous experiments, ontrol fruit took longer to soften when stored for 12 weeks ompred to pers stored for shorter periods.
134 J.H. Ekmn et l. / Posthrvest Biology nd Tehnology 31 (24) 127 136 3.2.2. Physiologil disorders None of the fruit in these experiments developed storge sld, internl rowning or signifint dey. The fruit used were erly seson pers, whih re generlly less suseptile to suh disorders, nd the storge times used were reltively short. However, it ws oserved tht fruit treted with 1-MCP were less suseptile to skin rowning fter ripening thn were the ontrol fruit. This ws not evident when the fruit were first exmined. However, hndling during mesurements of olor ws enough to use notiele skin rowning in ripe, untreted fruit. The sme hndling used less dmge in the 1-MCP treted pers. This differene ws still evident on fruit stored for 12 weeks, even though the effet of 1-MCP on ripening ws miniml. 3.2.3. Gs exhnge Ethylene nd CO 2 prodution t 1 C were signifintly higher in the ontrol fruit thn the 1-MCP CO 2 Prodution ( mol kg -1 h -1 ) Ethylene Prodution (nmol kg -1 h -1 ) 12 1 8 6 4 1 1 1 1.1 ontrol.2µl L -1, 4wk re-tret.4µl L -1, 4wk re-tret.2µl L -1, 6wk re-tret.4µl L -1, 6wk re-tret 2 4 6 8 1 12 Weeks in Storge t 1 C Fig. 6. CO 2 nd ethylene prodution during storge t 1 Cy pers treted with,.2 or.4 ll 1 of 1-MCP. Fruit were treted with 1-MCP fter hrvest nd following 4 or 6 weeks storge t 1 C. Error rs indite the stndrd devition of eh men (n = 3). treted fruit (Fig. 6 nd )(P<.1). The untreted fruit underwent limteri rise in ethylene prodution during storge t 1 C. Ethylene prodution y these fruit inresed 1-fold etween weeks 4 nd 8, then susequently deresed. Although tretment with 1-MCP suppressed ethylene prodution, rtes ontinued to inrese grdully while fruit were stored t 1 C. During the first 6 weeks of storge, no differenes in rtes of gs exhnge were oserved etween fruit treted with.2 or.4 ll 1 1-MCP. However, fter 6 weeks t 1 C, ethylene prodution nd respirtion rtes hd inresed in fruit treted with.2 ll 1 1-MCP ompred with those treted with.4 ll 1 1-MCP (P =.3). 4. Disussion Tretment with 1-MCP hd little or no effet on yellowing nd softening of Brtlett per fruit during storge t 1 C. However, exposure to 1-MCP slowed hnges during ripening. Respirtion nd ethylene prodution efore nd during ripening were lso inhiited, nd the inidene nd severity of superfiil sld nd internl rekdown were redued. However, the response of fruit to tretment ws highly dependent on the 1-MCP onentrtion pplied nd the period tht fruit were stored prior to ripening. In initil experiments, we treted fruit with etween.1 nd 1. ll 1 1-MCP. Although exposure to 1. ll 1 ompletely inhiited the development of sld nd internl rekdown, these fruit filed to soften normlly even fter 24 weeks in storge. Fruit treted with.5 ll 1 1-MCP did ripen during the experimentl period, lthough softening nd olor development were delyed. Tretment with.1 ll 1 hd some enefit in terms of reduing sld nd the rte of ripening in pers stored for up to 6 weeks. However, the effets were slight nd lost reltively quikly. Exposure to.1 ll 1 1-MCP hd no effet ompred with untreted fruit. From these results, we onluded tht 1-MCP tretment of etween.1 nd.5 ll 1 would e most likely to provide enefits in terms of mintining firmness nd reduing sld in storge, while still llowing pers to ripen in similr period of time s untreted fruit for mrketing nd onsumption.
J.H. Ekmn et l. / Posthrvest Biology nd Tehnology 31 (24) 127 136 135 In the susequent set of experiments, we treted pers with.2 or.4 ll 1 1-MCP. However, it ws pprent tht the effets of suh low onentrtions were likely to wer off within reltively short time. To oth ountert this prolem nd inrese mrketing flexiility, fruit were re-treted fter either 4 or 6 weeks, then stored for n dditionl 4 or 6 weeks. Re-treting fruit fter 4 weeks hd greter effet on the susequent rte of ripening thn did the initil 1-MCP pplition; yellowing nd softening were slower fter totl of 8 weeks storge t 1 C thn fter 4 weeks. It would seem possile tht regenertion of ethylene reeptors ws fster in freshly hrvested fruit ompred to pers stored for 4 weeks t 1 C. This ould explin why reovery of sensitivity to ethylene ws slower fter seond exposure to 1-MCP. In ontrst, re-treting fruit fter 6 weeks hd little dditionl effet on susequent ripening. It hs een found previously tht 1-MCP hs less effet when pplied to pers tht re lredy strting to ripen (Mttheis, 21). In this se, ethylene prodution hd inresed from rte of 1 3 nmol kg 1 h 1 fter 4 weeks storge to 9 13 nmol kg 1 h 1 fter 6 weeks storge. This suggests tht ripening proesses my hve lredy een initited in the fruit. The results support the onlusions of Hrris et l. (2), who found tht fruit mturity n hve lrge influene on the effets of exposure to 1-MCP. Some ommeril uyers of pers use skin olor s n inditor of the remining post-hrvest life of stored fruit. For pers to e mrketed suessfully to these uyers, they need to e predominntly green when removed from storge, with ripening ourring fterwrd. Even 1. ll 1 1-MCP filed to prevent yellow olor development when pers were stored for more thn 12 weeks. These results suggest tht storge of Brtlett pers for longer thn 3 months my e limited, irrespetive of 1-MCP tretment. However, this uyer is ginst yellow pers my e hnging s more ripe fruit re mrketed. Use of 1-MCP ould prove enefiil for Europen pers. Reduing the rte of ripening t mient tempertures my inrese the mrketle life of the fruit, prtiulrly in mrkets where the old hin is interrupted. Also, lthough the erly seson fruit used in the seond set of tretments did not develop superfiil sld within the experimentl period, it would seem likely from previous results tht even.4 ll 1 1-MCP ould redue the inidene of this disorder. Finlly, the oserved redution in skin rowning during hndling of ripe pers wrrnts further investigtion. Ripe pers re extremely sensitive to hndling, whih is the primry reson why fruit re usully sold prtilly green. However, in this se, 1-MCP onsiderly redued skin dmge without ffeting norml ripening. This ould prove of onsiderle enefit to the industry y reduing losses nd improving the pperne of mrketed pers. 5. Conlusion Brtlett pers re extremely sensitive to exposure to 1-MCP. However, the effets of 1-MCP re oth time nd onentrtion dependent. Further reserh is needed to understnd the ftors ffeting the responses of pers to re-tretment with 1-MCP. However, exposure to.2.4 ll 1 1-MCP ould prove enefiil y reduing physiologil disorders nd skin rowning, nd slowing the rte of ripening t room temperture. Referenes Britelle, A.L., Hyde, G.M., Fellmn, J.K., Vrith, J., 21. Using 1-MCP to inhiit the influene of ripening on impt properties of per nd pple tissue. Posthrvest Biol. Tehnol. 23, 153 16. Clypool, L.L., 1973. Further studies on ontrolled tmosphere storge of Brtlett pers. J. Am. So. Horti. Si. 98, 289 293. DeWild, H.P.J., Woltering, E.J., Peppelenos, H.W., 1999. Cron dioxide nd 1-MCP inhiit ethylene prodution nd respirtion of per fruit y different mehnisms. J. Exp. Bot. 5, 837 844. Fn, X., Mttheis, J.P., 1999. Development of pple superfiil sld, soft sld, ore flush, nd gresiness is redued y 1-MCP. J. Agri. Food Chem. 47, 363 368. Hrris, D.R., Seerry, J.A., Wills, R.B.H., Spohr, L.J., 2. Effet of fruit mturity on effiieny of 1-methylylopropene to dely the ripening of nns. Posthrvest Biol. Tehnol. 2, 33 38. Ju, Z., Cury, E.A., Dun, Y., Ju, Y., Guo, A., 21. Plnt oil emulsions prevent senesent sld nd ore rekdown nd redue fungl dey in Brtlett pers. J. Am. So. Horti. Si. 126, 358 363.
136 J.H. Ekmn et l. / Posthrvest Biology nd Tehnology 31 (24) 127 136 Kder, A.A., 1989. Mode of tion of oxygen nd ron dioxide on posthrvest physiology of Brtlett pers. At Horti. 258, 161 167. Meheriuk, M., Lu, O.L., 1988. Effet of two polymeri otings on fruit qulity of Brtlett nd d Anjou pers. J. Am. So. Horti. Si. 113, 222 226. Sisler, E.C., Serek, M., 1997. Inhiitors of ethylene responses in plnts t the reeptor level: reent developments. Physiol. Plnt. 1, 577 582. Wtkins, C.B., Nok, J.F., Whitker, B.D., 2. Responses of erly, mid nd lte seson pple ultivrs to posthrvest pplition of 1-methylylopropene (1-MCP) under ir nd ontrolled tmosphere onditions. Posthrvest Biol. Tehnol. 19, 17 32. Yoshid, T., Borgi, D.M., Chen, P.M., Mielke, E.A., 1986. Chnges in ethylene, ids, nd rown-ore development of Brtlett pers in low-oxygen storge. HortSiene 21, 472 474.