RESEARCH EFFECT OF HARVEST TIME AND L-CYSTEINE AS AN ANTIOXIDANT ON FLESH BROWNING OF FRESH-CUT CHERIMOYA (Annon cherimol Mill.) Reinldo Cmpos-Vrgs 1,*, Bruno G. Defilippi 1,, Pul Romero Q. 2, Héctor Vldés G. 3, Pul Roledo M. 4, nd Humerto Prieto E. 1 A B S T R A C T Browning development is the most importnt fctor limiting the qulity of fresh-cut cherimoy (Annon cherimol Mill.). However, there is little informtion ville out its cuses nd methods of control. The effectiveness of L-cysteine (0.125, 0.25 nd 0.5%) in fresh-cut cherimoy hrvested on two occsions (Octoer nd Novemer) nd stored for 6 nd 12 dys t 0 C ws studied. In order to understnd the iologicl sis of rowning, polyphenol oxidse (PPO) enzyme ctivity nd totl phenolic content in fresh-cut pieces were mesured. Qulity mesurements nd sensory nlysis indicted tht 0.5% L-cysteine ws somewht effective in reducing rowning development, without ffecting other qulity ttriutes. In terms of physiologicl prmeters, PPO ctivity did not show differences etween mture (t hrvest) nd ripe fruit (t processing) in oth hrvest times, ut cherimoy fruits picked in Novemer presented lower PPO ctivity thn fruit from Octoer. In generl, PPO ctivity nd totl phenolic content of L-cysteine treted fruits did not show consistent differences with untreted fruit t 6 or 12 dys t 0 C. PPO ctivity nlyses demonstrted tht PPO ctivity ws higher in the outer prt of cherimoy flesh compred to the middle or inner sector. These results would support the possiility of using L-cysteine s posthrvest tretment to reduce rowning development in fresh-cut cherimoy. Keywords: ntioxidnts, Annon cherimol, polyphenol oxidse, phenolics, sensoril evlution. INTRODUCTION The cherimoy is n exotic su-tropicl fruit with relevnt sensoril chrcteristics. Chile is one of the southern plces where cherimoys re grown commercilly in South Americ. Among cherimoy cultivrs present in Chile, Conch Lis is the most importnt nd hs een descried s more tolernt to low tempertures (Lhoz et l., 1993). This vriety hs een considered pproprite for export mrkets. However, fresh cherimoy export is restrictive ecuse of the fruit s high perishility nd susceptiility to chilling, forcing producers to use expensive irfreight (Plm et l., 1993). This sitution hs cused reduction in the numer of cherimoy orchrds, with the consequent replcement with more profitle fruit species. Minimlly processed fruits re emerging s new consumer trend sed on their convenience (Wills et l., 1998). Cherimoy fruit is suitle for fresh-cut processing, especilly considering its high numer of seeds, lrge size nd inedile peel, resulting in significnt non-edile proportion when consumed s whole fresh fruit. Therefore, the fresh cut modlity could e new nd more convenient wy to offer fresh cherimoy fruit to consumers. However, the informtion ville on cherimoy fruit is insufficient to estimte the chnges resulting from miniml processing. It is known tht the ehvior of fresh cut product could e different from tht of the sme product without processing (Wtd et l., 1996; Gorny, 1997). Therefore, the production of fresh-cut cherimoy implies the study of the effects of miniml processing (such s peeling, cutting, nd chunking) nd the chnges in ehvior of the cherimoy pieces s result of wounding. Cherimoy fruit is 1 Instituto de Investigciones Agropecuris, Centro Regionl de Investigción L Pltin, Csill 439/3, Sntigo, Chile. E-mil: rcmpos@ini.cl *Corresponding uthor. 2 Universidd de Ls Américs, Escuel de Agronomí, Mnuel Montt 948, Sntigo, Chile. 3 Universidd de L Seren, Fcultd de Ciencis, Cisterns 1200, L Seren, Chile. 4 Universidd de Chile, Fcultd de Ciencis Agronómics, Snt Ros 11315, Sntigo, Chile. Received: 21 June 2007. Accepted: 21 August 2007. CHILEAN JOURNAL OF AGRICULTURAL RESEARCH 68(3):217-227 (JULY-SEPTEMBER 2008)
218 CHILEAN J. AGRIC. RES. - VOL. 68 - N o 3-2008 prone to rowning (Mrtinez et l., 1993), which is considered one the most importnt oxidtive rections leding to loss of sensoril nd nutritionl qulity (Amiot et l., 1997). Studies hve reported cysteine s n inhiitor of enzymtic rowning in fruits (Amiot et l., 1997). Experiments with processed fruit including L-cysteine hve shown promising results in reducing the rowning prolem (Gorny et l., 2002; Melo nd Vils-Bos, 2006). Therefore, the ojective of this work ws to evlute the fruit hrvest time nd L-cysteine s strtegy for rowning reduction of minimlly processed cherimoy. MATERIALS AND METHODS Plnt mteril nd processing Fruit ws hrvested from Conch Lis cherimoy trees grown in commercil orchrd locted in Quillot Vlley, Chile (32 52 S, 71 15 W) in Octoer nd Novemer, 2005. The chnge in fruit ckground color from drk to light green ws considered s hrvesting index following technicl orchrd protocols. In generl, lrge to medium size fruits were selected nd trnsported to the posthrvest lortory fcilities t the Agriculturl Reserch Institute (INIA), Sntigo, for ripening nd preprtion. Preliminry studies showed tht fruit must e processed when cherimoy is fully ripe, with firmness vlues close to 1 kilogrm force (kgf), since pieces from mture (unripe) firm cherimoy did not follow norml ripening process during cold storge (dt not shown). Before processing, fruit ws wshed with 100 mg L -1 NOCl wter solution t room temperture to eliminte surfce contmintion. Then, fruit ws hnd-peeled with shrp knife, deseeded nd the pieces were immersed 2 min in solution contining n ntioxidnt compound, L-cysteine, nd then drined for 1 min. The L-cysteine solutions studied were 0.125, 0.25 nd 0.5% w/w. Fruit pieces from control tretment were immersed in wter nd drined for similr time. Fresh-cut cherimoys were stored in 0.5 L plstic continers t 0 C for 6 nd 12 d. For ll experiments fruit ws kept t 90-95% reltive humidity. Mturity nd qulity prmeters At hrvest, during the ripening process nd fter storge in cold room conditions, fruit mturity nd qulity prmeters were mesured. The firmness of the whole fruit ws evluted y using penetrometer (Fruit Pressure Tester, FT327, Alfonsine, Itly) with n 8 mm plunger on two opposite sides of the fruit previously peeled. Totl solule solids (TSS) were mesured y temperture-compensted refrctometer (ATAGO, ATC-1, Tokyo, Jpn) nd expressed s the percentge of solule solids in juice. Titrtle cidity (TA), expressed s mlic cid, ws determined y dding 0.2 N NOH to 10 ml cherimoy juice until ph 8.2 (Alique, 1995). Strch pttern ws mesured y sprying the cherimoy flesh with n iodine solution (24 g KI nd 12 g I 2 per liter doule distilled wter) nd rnking the color development in scle from 1 (high strch content) to 10 (very low strch content), in similr wy to tht used in pple strch index scoring (de Cstro et l., 2007). The sme methodology ws used for fresh cut pieces, with the exception of firmness nd strch content nlyses. The reltive concentrtion of solule o-quinones ws mesured s descried y Loiz-Velrde nd Sltveit (2001). Briefly, 10 g of cherimoy pulp ws ground with methnol (1:2), filtered nd centrifuged t 15 000 x g for 15 min. The superntnt ws mesured to 437 nm in spectrophotometer (Shimdzu UV-1700, Kyoto, Jpn). The fresh pulp color mesurement ws done using chrommeter (Minolt CR-300, Osk, Jpn), recording the dt in lightness (L*), chromticity (* nd *), Chrom ([(*) 2 + (*) 2 ] 0.5 ) nd Hue ngle (tn -1 [(*)(*) -1 ]). Physiologicl prmeters Immeditely fter hrvest nd efore processing, ethylene production nd respirtion rtes were determined in individul fruit using sttic system. Five fruits were weighed nd plced in 0.5 L jrs t 20 C. The jrs were seled for 3 h to otin gs smples. Cron dioxide concentrtions were mesured y injecting 1 ml hedspce smple in gs nlyzer (PIB Dnsensor Checkmte 9900, Ringsted, Denmrk). Ethylene ws mesured using gs chromtogrph (Shimdzu GC- 8A, Kyoto, Jpn) equipped with flme ioniztion detector (FID) nd n lumin column. Polyphenol oxidse (PPO) ctivity evlution PPO ctivity evlution ws done s descried y Siriphnich nd Kder (1985), with modifictions. Briefly, cherimoy fruit smples were otined nd frozen until preprtion. Four grms of cherimoy were ground in 12 ml uffer [0.1 M citric cid (ph 6.6), 5 mm 2-Me, 0.4 g polyvinylpolypirrolidone].
R. CAMPOS-VARGAS et l. - EFFECT OF HARVEST TIME AND L-CYSTEINE AS AN... 219 The mixture ws centrifuged t 20 000 x g for 10 min t 4 C. 0.1 ml of superntnt ws sved nd dded to 2.9 ml uffer [0.5 mm citric cid uffer (ph 6.6) nd 20 mm cthecol]. The ctivity ws mesured in Shimdzu UV-1700 spectrophotometer s product t 420 nm y 10 min t 25 C. The stright prt of the curve ws considered for ctivity clcultions. A lnk test contining only uffer or sustrte did not show chnges in sornce in the ssyed period. In ddition, the use of sodium dodecyl sulfte (SDS) t 0.6 mm (Rthjen nd Roinson, 1992) ws checked without oserving ny effect in PPO ctivity levels (dt not shown). Therefore, SDS ws not used in PPO ctivity nlyses. The unit for PPO enzyme ctivity (U) ws defined s the chnge of 0.001 sornce vlue under the descried conditions. Protein content of enzyme extrcts ws determined y the method of Brdford (1976), y using Bio-Rd protein ssy kit (Bio-Rd, Hercules, Cliforni, USA) nd ovine serum lumin (BSA) s stndrd. PPO ctivity ws expressed s U min -1 mg -1 totl protein. Sensory evlutions Sensoril evlutions were performed y pnel composed of 12 judges. Briefly, 40 g of fruit pieces from different tretments were tken nd plced in trys for evlutions in closed rooms. The methodology of descriptive tests ws followed (Pigentini et l., 2005), using scle from 0 to 15. For ppernce nd rom, 0 corresponded to unstisfctory nd 15 to stisfctory. In the cse of rowning development, 0 ment sound tissue nd 15 completely rown tissue. Totl phenolics Totl phenolic compounds were quntified y the Folin-Cioclteu spectrophotometric method (Singleton nd Rossi, 1965). Dt were reported s milligrms of p-coumric cid g -1 fresh weight (FW). Sttisticl nlysis There were three replictes (one pot of 800 g ech) for ll the evlutions. Dt were sujected to nlysis of vrince, nd mens were seprted y lest significnt difference (LSD) test t 5% significnce level using Sttgrphics Plus 5 (Mnugistics Inc., 2000). RESULTS AND DISCUSSION Mturity nd physiologicl prmeters Since the qulity of the fresh cut product relies on the chrcteristics of rw mteril, cherimoy fruits t two hrvest times (Octoer nd Novemer) were nlyzed, which permitted studying potentil chnges in physiologicl ehvior or fruit disorder susceptiility ssocited with environmentl chnges (Gonzlez- Aguilr et l., 2000; Cmpos-Vrgs et l., 2006). A remrkle loss of fruit firmness etween hrvest nd processing, with reduction close to 17-15 kgf, ws oserved t oth hrvest times (Tle 1). Totl solule solids content (TSS) in ripe fruit processed in Octoer or Novemer incresed sustntilly, douling the mount mesured in fruits just fter hrvest. These chnges re similr to those reported in other cherimoy studies (Lhoz et l., 1993; Alique et l., 1994; Snchez et l., 1998). The significnt increse in TSS could e due to the rekdown of strch t ripening (Mrtinez et l., 1993), s is supported y the high strch index vlue of ripe cherimoy fruit t oth hrvest times. Titrtle cidity (TA) levels, lthough low through ripening, incresed in ripe fruits in oth hrvest times. The rise of TA t ripening hs Tle 1. Mturity prmeters t hrvest (mture) nd efore processing (ripe) of cherimoy fruit hrvested in Octoer (Hrvest 1) nd Novemer (Hrvest 2). Time of evlution Firmness Totl solule solids Titrtle cidity Strch index 1 (1-10) kgf % % mlic cid Hrvest 1 At hrvest 18.20 6.2 0.1 1.0 At processing 1.06 15.4 0.3c 9.4c Hrvest 2 At hrvest 16.50 7.5 0.1 1.0 At processing 0.83 15.5 0.2 8.4 Mens followed y different letters re significntly different within the sme column for n individul prmeter ccording to LSD test (P 0.05). kgf: kilogrm force. 1 1 mens high strch content; 10 mens very low strch content.
220 CHILEAN J. AGRIC. RES. - VOL. 68 - N o 3-2008 een explined y the synthesis of mlic cid due to the ction of mlte dehydrogense ctivity s cherimoy fruit ripens (Muñoz et l., 2004). In terms of physiologicl prmeters, there ws progression of oth, ethylene nd respirtion rtes etween mture nd ripe cherimoy (Tle 2), following the expected pttern for climcteric fruit (Kder, 2002). It is interesting to oserve the mjor increse of ethylene production in Conch Lis cherimoy from undetectle levels t hrvest to remrkle mounts t processing. This high rte of ethylene production is lso shred with other cherimoy cultivrs, such s Fino de Jete (Mrtinez et l., 1993; Snchez et l., 1998), llowing thus the clssifiction of cherimoy fruit s very high ethylene producer (Kder, 2002). After processing, the qulity prmeters in fruit pieces were studied. TSS nd TA content fter 6 nd 12 d storge t 0 C from oth hrvest times, nd with different concentrtions of L-cysteine, did not show significnt chnges (dt not shown). This sitution cn e explined since the fruits were processed when the chnges ssocited with ripening were lredy ccomplished, otining the mximum solule solids nd cidity levels, which were mintined without chnges in storge due to the low temperture used in the experiment. It is interesting tht cherimoy, eing chilling sensitive fruit (Plm et l., 1993; Alique et l., 1994; Gutierrez et l., 1994), did not show reduction of solule solids or cidity, s seen in other situtions of chilling response (Mrrero nd Kder, 2006). Similrly, Gil et l. (2002), working in modified tmosphere pckging of fresh cut tomto (Lycopersicon esculentum Mill.), concluded tht the est temperture for keeping qulity ws 0 C, chilling condition for rw tomto. Cntwell nd Suslow (2002) stted tht the posthrvest life of fresh cut products prepred from chilled sensitive commodities is longer t 0 C thn t wrmer tempertures, since the deteriortion induced y low tempertures is less detrimentl thn decy t higher temperture. Browning development The L* (lightness) of tretments with L-cysteine ws not different from control fter 6 nd 12 d storge in hrvest 1 (Octoer) nd fter 6 d storge in hrvest 2 (Novemer) (Tle 3). For hrvest 2, only fter 12 d storge the L* vlue from 0.25 or 0.5% L-cysteine treted fruits ws different from control. As well, ll tretments t hrvest 1 nd 0.5% of L-cysteine in hrvest 2 were similr to L* t processing. This lck of shift in terms of L* in stored fresh cut cherimoy could e induced y reduction of lightness cused y chnges in the physicl or opticl properties of the flesh. Other reserchers hve reported tht L* ws not modified y ntioxidnt tretment in different fresh cut per (Pyrus communis L.) cultivrs, concluding tht chromticity * vlue ws the most effective to evlute color chnges (But nd Aott, 2000). The * vlues of 0.5% L-cysteine of hrvest 1, fter 6 or 12 d storge, nd hrvest 2 fter 6 d storge, were sttisticlly similr to those oserved t processing. Although * with 0.5% L-cysteine tretment fter 12 d storge in hrvest 2 ws different from cherimoy t processing, it ws rnked over the rest of the tretments. The results of * could e linked to the reduction of rowning development in cherimoy y L-cysteine. Other uthors hve descried tht * showed the est correltion with rowning in fresh cut pple (Mlus domestic Borkh.) nd lettuce (Lctuc stiv L.) (Roch nd Moris, 2001). Tle 2. Physiologicl prmeters t hrvest (mture) nd efore processing (ripe) of cherimoy fruits hrvested in Octoer (Hrvest 1) nd Novemer (Hrvest 2). Time of evlution Ethylene Respirtion rte production rte µl kg -1 h -1 ml CO 2 kg -1 h -1 Hrvest 1 At hrvest 0.0 17.8 At processing 56.4 53.7 Hrvest 2 At hrvest 0.0 12.1 At processing 76.8 53.9 Mens followed y different letters re significntly different within the sme column for n individul prmeter ccording to LSD test (P 0.05).
R. CAMPOS-VARGAS et l. - EFFECT OF HARVEST TIME AND L-CYSTEINE AS AN... 221 Tle 3. Color prmeters of fresh-cut cherimoy treted with L-cysteine nd stored for 6 nd 12 dys t 0 C of fruits hrvested in Octoer (Hrvest 1) nd Novemer (Hrvest 2). Color prmeters L* * * Chrom Hue 6 dys 12 dys 6 dys 12 dys 6 dys 12 dys 6 dys 12 dys 6 dys 12 dys Hrvest 1 Tretment At processing 90.3 90.3-0.9-0.9 10.7 10.7 10.7 10.7 94.9c 94.9c Control 74.9 72.7 2.0c 7.3 15.3 21.8c 15.3 23.1 82.3 73.0 0.125% L-cysteine 73.1 69.8 6.0d 14.1c 15.0 18.8c 15.8 23.5 68.8 54.0 0.25% L-cysteine 77.4 69.2 3.1c 7.6 15.3 14.0 15.6 16.0 79.1 61.6 0.50% L-cysteine 70.4 69.4 0.6 3.3 13.4 11.6 13.4 12.4 89.5c 74.0 Hrvest 2 At processing 82.1 82.1d -1.2-1.2 13.5 13.6 13.7 13.7 95.2c 95.2d Control 73.9 51.9 5.2 13.4c 20.4c 29.9 21.1c 33.0c 76.0 65.7c 0.125% L-cysteine 71.1 60.8 4.9 16.2c 12.7 17.8 13.7 24.1 69.7 48.1 0.25% L-cysteine 65.9 67.2c 7.0 12.6c 13.4 17.0 15.6c 21.5 67.8 55.7 0.50% L-cysteine 68.9 76.8cd -0.3 3.7 9.3 13.3 9.3 13.9 92.9c 75.7c Mens followed y different letters re significntly different within the sme column for n individul prmeter ccording to LSD test (P 0.05). The chromticity * vlue from 0.5% L-cysteine tretments showed trend to present lower vlues thn the rest of the tretments nd similr to those oserved t processing. In reltion to Chrom, excluding the evlution fter 6 d in hrvest 1, vlues of tretments with 0.5% L-cysteine were similr to cherimoy t processing. Hue ngles of cherimoys t processing were similr to those treted with 0.5% of cysteine nd stored for 6 d t 0 C for oth hrvest times. However, hue ngles of cherimoy stored for 12 d with L-cysteine were lower thn t processing, with no evident pttern, proly due to the intense rowning registered in ll tretments (Figure 1). The inconsistent effect of 0.125 nd 0.25% L-cysteine could e explined y n insufficient mount of L-cysteine chieving cysteine:phenolic rtio pproprite for inducing synthesis of colored products y o-quinone rections (Amiot et l., 1997). The sensory evlution of rom, ppernce nd rowning of fresh cut cherimoy is shown in Figure 1. Arom ws not ffected y tretments or low temperture s judged y the pnel in oth hrvest times, which is highly desirle since L-cysteine tretments did not dd off-odors to cherimoy. The highest score of ppernce ws otined from cherimoy fruits treted with incresing concentrtions of L-cysteine in oth hrvest times. The tretment with 0.5% L- cysteine ws more effective thn others in reducing rowning in short- or long-term storge. However, fter 12 d, the overll visul qulity ws lower thn fter 6 d t 0 C. A higher intensity of rowning ws oserved in pieces otined from the outer zone of the fruit (elow the rind) thn from other zones in the flesh. As stted y judges, tretments with 0.125 nd 0.25% L-cysteine lso reduced rowning development, lthough the highest concentrtion ws more consistent in ccordnce with the instrumentl nlyses dt in Tle 3. Interestingly, L-cysteine tretments did not ffect tste of cherimoy pieces, s stted y judges (dt not shown). The ction of L-cysteine s n inhiitor of rowning development hs een referred to in its cpcity for duction of phenolic compounds, reduction of o-quinones to diphenols, competitive inhiition of PPO nd phenol regenertion (Richrd- Forget et l., 1992). These dt suggest tht L-cysteine t 0.5% could e promising ntioxidnt tretment in cherimoy. However, our dt contrst with those otined y Mrtinez-Cyuel et l. (1988), who concluded tht thiol compounds, such s L-cysteine, could not inhiit rowning in cherimoy. The lck of correltion etween instrumentl nd sensoril results could e induced y the nture of the cherimoy
222 CHILEAN J. AGRIC. RES. - VOL. 68 - N o 3-2008 Arom 14 12 10 8 6 Control 0.125% cysteine 0.25% cysteine 0.5% cysteine () () 4 2 Appernce 0 14 12 10 8 6 4 () () 2 Browning 0 14 12 10 8 6 () c c c () 4 2 0 6 12 6 12 Dys t 0 ºC Dys t 0 ºC Figure 1. Sensory evlutions from fresh-cut cherimoy treted with L-cysteine nd stored for 6 nd 12 d t 0 C. Hrvest Octoer () nd Novemer (). For ppernce nd rom 0 corresponds to unstisfctory nd 15 to stisfctory. In the cse of rowning development 0 mens sound tissue nd 15 completely rown tissue. Mens followed y different letters re significntly different ccording to LSD test (P 0.05). flesh, s stted efore, nd the fct tht cherimoy is n ggregte fruit (derived from single flower with severl pistils). Therefore, the judges could hve more integrl view of the generl spect of the pieces nd the instrumentl dt nlyses could e interfered with y the type of tissue smpled in terms of topologicl locliztion in the cherimoy flesh (close to the core or the outside prt of the fruit). Totl phenolics nd PPO ctivity The totl phenolic content from fruit hrvested in Octoer did not show significnt chnges etween mture (t hrvest) nd ripe fruit (t processing) (Tle 4). The sence of differences etween mturity stges hs een reported y Assis et l. (2001). However, phenolic content of mture cherimoys hrvested in Novemer showed lower vlues thn ripe fruits. In ddition, cherimoys from the second hrvest hd lower levels of totl phenolics t the mture stge thn fruit picked in Octoer, ut fter ripening oth hrvests were similr. These differences could e due to the different environmentl conditions in which they were grown, which could e ffecting the phenolic content (Kder, 2002).
R. CAMPOS-VARGAS et l. - EFFECT OF HARVEST TIME AND L-CYSTEINE AS AN... 223 Despite the sence of sttisticl differences in PPO ctivity etween mture (t hrvest) nd ripe fruit (t processing) for oth hrvest times (Tle 4), the enzyme ctivity levels of mture or ripe fruits hrvested in Octoer were significntly higher thn of those picked lter in Novemer, which could e explined s result of more fvorle environmentl conditions lter in the seson, which influence cherimoy metolism nlogous to the explntion for phenolic content. The lck of sttisticl difference in PPO ctivity relted to ripening progress hs een oserved in other fruits (Vlentines et l., 2005). A reltion etween PPO ctivity nd totl phenolic content in cherimoy hrvested on Octoer or Novemer ws not evident (Tle 4). The ltter could indicte tht the synthesis of phenolic compound does not present direct reltionship to PPO ctivity, s reported with other fruits. Roch nd Moris (2001) reported R 2 = 0.29 etween phenolic content nd PPO ctivity in minimlly processed pples. According to Cheng nd Crisosto (1995), PPO ctivity did not correlte with rowning potentil in pech (Prunus persic (L.) Btsch) nd nectrine skins. The phenolic content nd PPO ctivity of fresh-cut cherimoy fter 6 nd 12 d storge t 0 C is shown in Tle 5. The totl phenolic content in oth hrvests did not show consistent trend. In hrvest 1, fter 6 d, totl phenolics of untreted fruit did not differ from tht of fruit treted with different percentges of L-cysteine, ut fter 12 d non-treted fruit hd less phenolic compounds thn 0.5% L-cysteine-treted fruit. The ltter contrsts with hrvest 2 dt, where fter 6 d the control showed less totl phenolics thn the tretment with 0.5% L-cysteine, ut fter 12 d ll tretments were sttisticlly similr. However, totl phenolics for ll tretments fter 6 d were higher thn Tle 4. Totl phenolics nd polyphenol oxidse (PPO) ctivity t hrvest (mture) nd efore processing (ripe) of cherimoy fruits picked in Octoer nd Novemer. Evlution Totl phenolics PPO ctivity Octoer Novemer Octoer Novemer µg g (FW) -1 U min -1 mg -1 totl protein At hrvest 103.4A 63.1B 4282A 1007B At processing 117.8A 97.7A 2988A 675B Mens followed y different lower-cse letters re significntly different within the sme column nd cpitl letter within the sme row for n individul prmeter ccording to LSD test (P 0.05). FW: fresh weight. Tle 5. Totl phenolics nd polyphenol oxidse (PPO) ctivity of fresh-cut cherimoy fruits treted with L-cysteine nd stored for 6 nd 12 dys t 0 C of fruits hrvested in Octoer (Hrvest 1) nd Novemer (Hrvest 2). Tretment Totl phenolics PPO ctivity 6 dys 12 dys 6 dys 12 dys µg g -1 FW U min -1 mg -1 totl protein Hrvest 1 Control 127.9 92.3 2926 1944 0.125% L-cysteine 105.0 88.7 2448 1517 0.25% L-cysteine 128.0 112.5 1867 1631 0.5% L-cysteine 153.7 135.6 1680 1005 Hrvest 2 Control 135.8 81.7 1724 1232 0.125% L-cysteine 134.0 92.3 1056 1156 0.25% L-cysteine 143.7 83.4 1221 765 0.5% L-cysteine 173.8 95.8 470 979 Mens followed y different letters re significntly different within the sme column nd hrvest time for n individul prmeter ccording to LSD test (P 0.05). FW: fresh weight.
224 CHILEAN J. AGRIC. RES. - VOL. 68 - N o 3-2008 fter 12 d in oth hrvests, proly s result of the reduction of the pool of phenolics y polymeriztion ending in rown compounds or other rections. This pttern of increse of totl phenolic contents followed y reduction hs een descried in cues of pple stored t 4 C (Roch nd Moris, 2001). In generl, PPO ctivity levels of minimlly processed cherimoy (Tle 5) treted nd non-treted with ntioxidnt solution were not sttisticlly different. Couture et l. (1993) working with fresh cut lettuce reported no chnges in PPO ctivity fter 4 d t 2.5 C. Similrly, Ke nd Sltveit (1989) did not oserve chnges in PPO ctivity fter wounding of iceerg lettuce (Lctuc stiv L.). The reson why only cherimoy treted with 0.5% L-cysteine hd significntly lower PPO ctivity thn control fter 6 d in hrvest 1 is uncler. An explntion could e tht cherimoy ctully corresponds to syncrpium fruit (Plm et l., 1993); therefore, dt represents PPO ctivity of severl fruitlets providing n extr level of complexity in the nlysis s oserved previously for other metolic processes (Bile nd Brcus, 1970). As mentioned ove, rowning development ws higher in pieces otined close to the peel thn in the inner prt of the fruit. In order to understnd this sitution, totl phenolic content nd PPO ctivity were mesured in tissue derived from different positions in the flesh (Tle 6). Phenolic contents were sttisticlly higher in tissue from outer thn inner or middle prts of the fruit. The sme pttern ws shown fter 4 h t 20 C, ut pieces from outer nd middle prts of the fruit showed n increse of totl phenolics with lmost null chnges in the inner prt. PPO ctivity of the sme pieces showed higher vlues in the outer nd middle flesh t time 0, with lower level in the inner zone. After exposing pieces to ir t 20 C for 4 h, PPO ctivity in the outer prt douled the levels oserved t time 0, explining prtilly the rise in totl phenolic content recorded in this zone of the fruit. The PPO ctivity of the middle or inner prt did not show mjor increment nd remined low. These results would suggest differentil susceptiility to rowning of cherimoy fruit zones. Snchez de Medin et l. (1986) reported higher PPO ctivity in exocrp thn mesocrp in cherimoy cv. Fino de Jete. Rivs nd Whitker (1973) purified PPO from per peel ecuse this tissue hd significntly more ctivity thn pulp. Gooding et l. (2001) descried in full size green nns (Mus x prdisic L.) lmost doule PPO ctivity in the peel thn the pulp. Rthjen nd Roinson (1992) found higher PPO ctivity in skin compred with pulp in grpe (Vitis vinifer L.) erries Sultn H5. Jpnese pples showed the highest PPO ctivity in the core, followed y the flesh nd then the peel (Wkym, 1995). CONCLUSIONS This work reported the complexity of cherimoy fruits s fresh cut product nd the physiologicl chnges induced y processing. In generl, PPO ctivity of cherimoy hrvested in Novemer ws lower thn tht mesured in Octoer. In ddition, the inner prt of the fruit showed less PPO ctivity nd phenolic compounds thn the tissue close to the peel, suggesting topologicl differences in cherimoy flesh. Besides, fresh cut cherimoy pieces were less rown t 6 thn 12 d sed on Hue ngle dt. Although the instrumentl color nlyses showed low correltion with the sensoril pnel dt, it is possile to conclude tht low temperture nd L-cysteine re suitle tools to keep the qulity of fresh cut cherimoy y reducing the rowning process. However, in future works it is required to find etter techniques to instrumentlly quntify color chnges in cherimoy smples. Tle 6. Totl phenolics nd polyphenol oxidse (PPO) ctivity of cherimoy tissues fter 4 h t 20 C. Fruit tissue Totl phenolics PPO ctivity 0 h 4 h 0 h 4 h µg g -1 FW U min -1 mg -1 totl protein Outer 104.6 123.2 6961 12911 Middle 85.0 97.7 5662 4950 Inner 86.3 85.1 2183 3581 Mens followed y different letters re significntly different within the sme column nd hrvest time for n individul prmeter ccording to LSD test (P 0.05). FW: fresh weight
R. CAMPOS-VARGAS et l. - EFFECT OF HARVEST TIME AND L-CYSTEINE AS AN... 225 R E S U M E N Efecto del momento de cosech y L-cisteín como un ntioxidnte en el prdemiento de pulp de chirimoy (Annon cherimol Mill.) precortd. Reinldo Cmpos-Vrgs 1,*, Bruno G. Defilippi 1, Pul Romero Q. 2, Héctor Vldés G. 3, Pul Roledo M. 4, y Humerto Prieto E. El desrrollo de prdemiento es uno de los fctores limitntes en l clidd de chirimoy (Annon cherimol Mill.) precortd (fresh-cut). No ostnte, existe poc informción disponile en relción sus cuss y métodos de control en est frut. Se estudió l efectividd de L-cisteín (0,125; 0,25 y 0,5%) en chirimoy precortd cosechd en dos oportuniddes (octure y noviemre) y lmcend por 6 y 12 dís 0 C. Con el ojetivo de conocer ls ses iológics del prdemiento, se estudió l ctividd de polifenol oxids (PPO) y contenido de fenólicos totles en piezs resultntes del precortdo. Ls mediciones de clidd y nálisis sensoril indicron que el trtmiento 0,5% L-cisteín fue el más efectivo en reducir el desrrollo de prdemiento sin fectr otros triutos de clidd. En términos de prámetros fisiológicos, l ctividd de PPO no mostró diferencis entre frutos inmduros ( l cosech) y mduros (l procesmiento) en ms cosechs. Sin emrgo, chirimoys cosechds en noviemre presentron niveles de ctividd de PPO menores que en octure. En generl, l ctividd de PPO y contenido totl de fenoles de frutos trtdos con L-cisteín no presentron diferencis significtivs con respecto frutos no trtdos después de 6 ó 12 dís 0 C. Los nálisis de l ctividd de PPO demostrron que ést fue más lt en l prte extern de l pulp que en el sector medio o interno. Estos resultdos respldrín l posiilidd de usr L-cisteín como un trtmiento de poscosech pr reducir el desrrollo de prdemiento en chirimoy destind precortdo. Plrs clve: ntioxidntes, Annon cherimol, polifenol oxids, fenólicos, evlución sensoril. ACKNOWLEDGEMENTS This work ws funded y project FONDECYT 1040011. LITERATURE CITED Alique, R. 1995. Residul effects of short-term tretments with high-co 2 on the ripening of cherimoy (Annon cherimol Mill.) fruit. J. Hortic. Sci. 70:609-615. Alique, R., J.P. Zmorno, M.L. Clvo, C. Merodio, nd J. De l Plz. 1994. Tolernce of cherimoy (Annon cherimol Mill.) to cold storge. J. Amer. Soc. Hort. Sci. 119:524-528. Amiot, M.J., A. Fleuriet, V. Cheynier, nd J. Nicols. 1997. Phenolic compounds nd oxidtive mechnism in fruit nd vegetles. p. 51-85. In Toms-Brern, F.A., nd R.J. Roins (eds.) Phytochemistry of fruit nd vegetles. Oxford University Press, New York, USA. Assis, J.S., R. Mldondo, T. Muñoz, M.I. Escrino, nd C. Merodio. 2001. Effect of high cron dioxide concentrtion on PAL ctivity nd phenolic contents in ripening cherimoy fruit. Posthrvest Biol. Technol. 23:33-39. Bile, J.B., nd D.E. Brcus. 1970. Respirtion ptterns in tropicl fruits of the Amzon sin. Trop. Sci. 12:93-104. Brdford, M.M. 1976. A rpid nd sensitive method for the quntifiction of microgrm quntities of protein utilizing the principle of protein-dye inding. Anl. Biochem. 72:248-254. But, J.G., nd J.A. Aott. 2000. Browning inhiition of fresh-cut Anjou, Brtlett nd Bosc pers. HortScience 35:1111-1113. Cmpos-Vrgs, R., O. Becerr, R. Bez-Ytes, V. Cmizo, M. Gonzlez, A. Orelln et l. 2006. Sesonl vrition in the development of chilling injury in O Henry peches. Sci. Hortic. 110:79-83. Cntwell, M., nd T. Suslow. 2002. Posthrvest hndling systems: Minimlly processed fruits nd vegetles. p. 445-463. In A.A. Kder (ed.) Posthrvest technology of horticulturl crops. University of Cliforni. Agriculture nd Nturl Resources. Puliction 3311. University of Cliforni, Oklnd, Cliforni, USA. Cheng, W.C., nd C.H. Crisosto. 1995. Browning potentil, phenolic composition, nd polyphenoloxidse ctivity of uffer extrcts of pech nd nectrine skin tissue. J. Amer. Soc. Hort. Sci. 120:835-838. Couture, R., M.I. Cntwell, D. Ke, nd M.E. Sltveit. 1993. Physiologicl ttriutes relted to qulity ttriutes nd storge life of minimlly processed lettuce. HortScience 28:723-725. Gil, M.I., M.A. Cones, nd F. Artes. 2002. Qulity chnges in fresh cut tomto s ffected y modified tmosphere pckging. Posthrvest Biol. Technol. 25:199-207.
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