Posthrvest Appliction of 1-Methylcyclopropene (1-MCP) Extends Shelf Life of Kiwifruit C.M. Cntin 1, D. Holcroft 2 nd C.H. Crisosto 1 1 University of Cliforni, Dvis, Deprtment of Plnt Sciences, Dvis, CA 9616, USA 2 AgroFresh Inc., Dvis, CA 9618, USA Keywords: Actinidi delicios, firmness, posthrvest qulity Astrct The role of posthrvest ppliction of 1-methylcyclopropene (1-MCP) in the softening of Hywrd kiwifruit under different cold storge conditions ws investigted. 1-MCP treted fruit (.,., 1. µl L -1 ) were kept in cold storge (1 C) up to 6 months efore ripening. Different 1-MCP ppliction times were lso tested in this tril (12 nd 24 h). Effect of 1-MCP under ethylene-free tmosphere nd under ethylene contminted tmosphere during storge ws investigted. Under oth conditions, 1-MCP tretment significntly delyed the rte of fruit softening during cold storge. Firmness out of cold storge ws significntly incresed y 1- MCP tretments. Moreover, the numer of dys of shelf life t 2 C (fter 4 nd 6 months of cold storge t 1 C) needed y Hywrd kiwifruit to rech flesh firmness 1 N ws significntly incresed y 1-MCP posthrvest tretment. These dt show tht 1-MCP tretment recommendtions for n optiml result depend on oth the length of cold storge s well s ethylene contmintion of the tmosphere during storge. INTRODUCTION The ethylene ction inhiitor 1-MCP, which locks the ethylene receptors, hs een extensively studied to regulte fruit ripening in oth climcteric nd non-climcteric fruits (Dong et l., 22; Jung nd Lee, 29; Khn nd Singh, 29; Lrrigudière et l., 29). Effect of 1-MCP on delying softening of fruit hs een reported to depend upon the fruit mturity stge t hrvest (Vlero et l., 23), concentrtion pplied (Slvdor et l., 2), durtion of fruit exposure to 1-MCP (Adi et l., 1998; Dong et l., 22), method of ppliction (Khn nd Singh, 29; Mngnris, 27), storge conditions nd fruit temperture t the time of 1-MCP ppliction (Adi et l., 1998). The ojectives of this work were to evlute the role of posthrvest ppliction of 1-MCP in modulting mrket life under different storge conditions, nd find the est 1- MCP concentrtion nd exposure time to e pplied for kiwifruit. MATERIAL AND METHODS Plnt Mteril nd 1-MCP Appliction Kiwifruit (Actinidi delicios Hywrd ) were hrvested, trnsported to the lortory, nd immeditely plced in hermeticlly seled steel tnks (33 L) t 1 C nd different concentrtions of 1-MCP (.,., 1. µl L -1 ) nd durtions (12 or 24 h). 1-MCP ws otined from AgroFresh Inc. (SmrtFresh Qulity System). Following the 1-MCP tretments, hlf of the fruit from ech tretment comintion were stored in cold room with 1. µl L -1 ethylene (externl contmintion), nd the other hlf in room with n ir exchnge of one tnk volume per 6 h in order to remove ny ethylene produced y the fruit, oth t 1 C. Fruit Firmness After, 2, 4 nd 6 months of storge t 1 C (with or without ethylene), 1 ox from ech tretment ws moved to 2 C to e evluted during shelf life. 1 fruit from ech tretment were evluted for flesh firmness every 2 dys until softening reched 1 N. Fruit firmness ws determined y penetrometer fitted with n 8-mm tip. After Proc. VII th IS on Kiwifruit Eds.: G. Cost nd A.R. Ferguson Act Hort. 913, ISHS 211 621
removing thin slice of fruit skin (~3 mm), firmness ws recorded from oth sides of ech fruit nd mens were expressed s Newtons (N). Sttisticl Anlysis All sttisticl nlyses were performed using SPSS 17. for Windows (SPSS, Chicgo, IL, USA). Duncn s multiple-rnge test (P.1) ws used to estimte tretment mens nd to find differences mong them. RESULTS As expected, contmintion with ethylene during the cold storge ccelerted the decrese of fruit firmness of oth fruit treted or non-treted with 1-MCP (Tle 1 nd Figs. 1 nd 2). However, tretment with 1-MCP extended the shelf life of kiwifruit y mintining firmness oth in fruit free of ethylene nd in fruit contminted with ethylene (1. µl L -1 ) during the cold storge time, for ll the storge time tested (6, 12 nd 18 d) (Tle 1). This result demonstrtes tht tretment with 1-MCP induces n extension of shelf life of fruit even if the fruit suffer from contmintion of ethylene during the cold storge due to the ethylene production y other commodities. After 12 d of storge, no significnt differences in terms of fruit flesh firmness out of the storge were found mong different 1-MCP tretments (Tle 1). Therefore, 1-MCP concentrtion of. µl L -1 tretment during n exposure time of 12 h is recommended for cold storge periods up to 6 d. However fter 12 d of cold storge, significnt differences were found mong different 1-MCP concentrtion nd exposure time comintions (Tle 1). In the fruit free of ethylene during ll the storge durtion, 1. µl L -1 1-MCP treted fruit (for 12 or 24 h) showed the highest firmness fter 12 d of cold storge t 2 C, without eing significntly different from fruit treted with. µl L -1 for 12 h. However, when the fruit ws contminted with ethylene during the colds storge, oth 1-MCP tretments with longer exposure time (. nd 1. µl L -1 for 24 h) showed the highest fruit firmness fter 12 d of cold storge. Thus, inhiition of ethylene effects on ripening y inding to ethylene receptors is etter chieved y 1-MCP when the exposure time is longer. Therefore, 24 h of exposure would e recommended when the fruit is thought to e stored with ethylene-producing commodities, wheres 12 h of exposure would e enough when kiwifruit is thought to e free of ethylene contmintion during storge. After 18 d of cold storge, ll 1-MCP tretments incresed the firmness of the fruit (Tle 1) lthough no significnt differences were found on fruit firmness etween different 1-MCP tretments just fter removing the fruit from cold storge. However, differences ecme significnt during shelf life t 2 C. The firmness evolution of kiwifruit during shelf life t 2 C fter 6, 12 nd 18 d of cold storge ws lso improved y 1-MCP tretments. After 4 months, the ethylene-free fruit did not show consistent differences in terms of fruit firmness mong different 1-MCP tretments. However, untreted fruit softened much fster thn 1-MCP treted fruit, reching less thn 1 N of flesh firmness t dy 4 of shelf life, wheres 1-MCP treted fruit showed firmness higher thn 1 N until the dy 1 of shelf life (results not shown). Therefore, 1-MCP tretments showed n extension of shelf life of out 6 dys on the kiwifruit not contminted with ethylene during the cold storge. The lck of consistent differences mong different 1-MCP tretments, points out. µl L -1 of 1-MCP pplied on the fruit during 12 h s the est tretment to e pplied on kiwifruit tht is going to e ethylene-free during storge. Tretment with 1-MCP lso showed drmtic effect on the firmness evolution of kiwifruit during shelf life fter 12 d of cold storge. Untreted fruit hd firmness vlue elow N out of cold storge, wheres fruit treted with 1-MCP mintined flesh firmness vlue ove 1 N pproximtely until dy 8 of shelf life t 2 C. Besides tht, there were significnt differences mong 1-MCP tretments in terms of fruit softening. Differences seen in the firmness out of the cold storge were mintined consistently long the whole shelf life period, showing tht 24 h of exposure to 1-MCP hs eneficil 622
effects on the mintennce of firmness in kiwifruit contminted with ethylene during storge. Thus, s commented ove, tretment with. µl L -1 of 1-MCP with n exposure time of 24 h is the tretment recommended for kiwifruit suspected to e contminted y ethylene from other commodities during cold storge. Similr results were found fter six months of cold storge (Fig. 1). 1-MCP treted fruit showed significntly higher firmness t ll the times mesured during shelf life (from dy to dy 8) on oth ethylene-free (Fig. 1) or ethylene-contminted fruit (Fig. 1). However, the effect of different 1-MCP tretments on the softening of the fruit ws very similr, without showing significnt differences etween different concentrtions or ppliction times. This could e due to the fct tht, immeditely fter the cold storge period, the 1-MCP treted fruit firmness ws lredy round 1-12 N, nd therefore the rnge of softening to find differences etween tretments ws much lower thn fter 4 months. It is importnt to notice tht lthough firmness ws mintined y 1-MCP during storge, the tretment does not prevent the softening of the fruit during shelf life to rech proper firmness for consumption. The numer of dys of shelf life t 2 C needed to rech the minimum firmness vlue cceptle for consumption ( 1 N) fter 18 dys of cold storge t 2 C is shown in Figure 2. Results re similr to wht hppened fter four months of cold storge, lthough in tht cse the fruit ws firmer. Untreted fruit firmness ws elow 1 N when cme out from the cold storge, either with or without ethylene contmintion during storge. On oth the ethylene-free (Fig. 2) nd ethylene-contminted fruit (Fig. 2), fruit treted with. µl L -1 of 1-MCP pplied for 24 h showed the higher numer of dys to rech 1N. No improvement ws chieved when pplying higher concentrtion (1 µl L -1 24 h). However, n extension of shelf life resulted from treting the fruit during 24 h when compred to the tretment for 12 h. Therefore, fter 18 d of cold storge, the est results were chieved when treting the fruit with. µl L -1 of 1-MCP pplied for 24 h, no mtter if the fruit ws or not stored in free or ethylene-contminted tmosphere. CONCLUSIONS The results of this work show tht tretment with 1-MCP extended the shelf life of kiwifruit y mintining firmness oth in fruit free of ethylene nd in fruit contminted with ethylene (1. µl L -1 ) during the cold storge time up to 4 months. This mens tht tretment with 1-MCP induces n extension of shelf life of kiwifruit even if the fruit suffer from contmintion of ethylene during the cold storge due to the ethylene production y other commodities. The results of this work lso show tht the 1-MCP protocol to follow to extend the shelf life of kiwifruit depends on the length nd type of storge tht is going to e performed with the fruit. For short periods of cold storge (up to 6 d), the lck of improvement of the 1-MCP tretment when pplying higher concentrtions, or for longer periods of time, points out tht. µl L -1 of 1-MCP during 12 h pplied just fter hrvest would e the recommended protocol to use. On the other hnd, when the period of time to e stored is longer thn 6 dys, the protocol to follow it will depend on if the fruit is free of ethylene contmintion during cold storge or not. If the fruit will e stored with no ny other commodity, nd potentil ethylene contmintion in the storge tmosphere is going to e removed, n ppliction of. µl L -1 of 1-MCP during 12 h will e the est protocol to follow on kiwifruit. However, if the fruit is suspected to e in contct to ethylene produced either y the kiwifruit or y other commodities in the sme cold room, 1-MCP exposure time should e incresed to 24 h, nd slightly etter results would e otined y incresing lso the concentrtion to 1 µl L -1. Optimiztion of posthrvest pplictions of 1-MCP on the kiwifruit, nd the eneficil effects of this prctice on the shelf life of this commodity hs een chieved with this work. 623
Literture Cited Adi, N., McGlsson, W.B., Holford, P., Willims, M. nd Mizrhi, Y. 1998. Responses of climcteric nd suppressed-climcteric plums to tretment with propylene nd 1- methylcyclopropene. Posthrvest Biol. Technol.14:29-39. Dong, L., Lurie, S. nd Zhou, H.W. 22. Effect of 1-methylcyclopropene on ripening of Cnino pricots nd Royl Zee plums. Posthrvest Biol. Technol.24:13-14. Jung, S.K. nd Lee, J.M. 29. Effects of 1-methylcyclopropene (1-MCP) on ripening of pple fruit without cold storge. J. Hort. Sci. Biotechnol. 84:12-16. Khn, A.S. nd Singh, Z. 29. 1-MCP ppliction suppresses ethylene iosynthesis nd retrds fruit softening during cold storge of Tegn Blue Jpnese plum. Plnt Sci. 176:39-44. Lrrigudière, C., Cndn, A.P., Uch, D. nd Grell, J. 29. Physiologicl response of Lrry Ann plums to cold storge nd 1-MCP tretment. Posthrvest Biol. Technol. 1:6-61. Mngnris, G.A. 27. Effect of dips in 1-methylcyclopropene-generting solution on Hrrow Sun plums stored under different temperture regimes. J. Agri. Food Chem. :71-72. Slvdor, A., Cuquerell, J. nd Úed, S. 2. Effect of 1-Methylcyclopropene on the posthrvest life of persimmon CV. Rojo Brillnte. J. Options Mediterrneennes 1:119-122. Vlero, D., Mrtinez-Romero, D., Vlverde, J.M., Guillen, F. nd Serrno, M. 23. Qulity improvement nd extension of shelf life y 1-methylcyclopropene in plum s ffected y ripening stge t hrvest. Innovtive Food Sci. Emerging Technol. 4:339-348. Tles Tle 1. Effect of 1-MCP on the Hywrd kiwifruit flesh firmness (N) fter 6, 12 nd 18 dys of cold storge (1 C). Fruit were treted with different 1-MCP concentrtion nd ppliction time comintions. Tretments were split into two su-tretments: fruit exposed to ir with flux of 1 L/min during storge (no ethylene exposure), nd fruit exposed to 1. µl L -1 ethylene with flux of 1 L/min during storge. Dt re mens of ten replictes. Tretment fter 6 d cold storge Firmness (N) fter 12 d cold storge fter 18 d cold storge No ethylene exposure during cold storge Control 2.46 11.79 c 7.4 1-MCP. L L -1 (12h) 32.92 1.7 1.9 1-MCP 1 L L -1 (12h) 31.47 17.46 12.1 1-MCP. L L -1 (24h) 29.91 13.1 c 12.23 1-MCP 1 L L -1 (24h) 31.14 16.3 11.7 Ethylene exposure during cold storge Control 3.38 4.4 c 2.78 1-MCP. L L -1 (12h) 3.14 11.23 11.1 1-MCP 1 L L -1 (12h) 28.2 11.34 11.68 1-MCP. L L -1 (24h) 24.69 13.9 1.6 1-MCP 1 L L -1 (24h) 26.91 13.9 11.23 For ech su-tretment (with or without ethylene exposure during cold storge), mens with the sme letter re not significntly different ccording to Duncn s test (P.1). 624
Figures 2 Control 1-MCP ( pp/12h) 1-MCP (1 pp/12h) Flesh Firmness (N) 1 1 1-MCP ( pp/24h) 1-MCP (1 pp/24h) 2 Flesh Firmness (N) 1 1 c c Dy Dy 2 Dy 4 Dy 6 Dy 8 Fig. 1. Effect of 1-MCP on the flesh firmness evolution of Hywrd kiwifruit during 12 dys t 2 C fter 18 d of cold storge (1 C). During cold storge, () ir ws continuously renovted (1 L/min) to prevent exposure of the fruit to ethylene; () fruit ws exposed to 1. µl L -1 ethylene with flux of 1 L/min. Ech dt point is the men of ten replictes. 62
Dys to rech flesh firmness < 1 N 2 2 1 1 Dys to rech flesh firmness < 1 N 2 2 1 1 Control. L/L 1 L/L. L/L 1 L/L 12 h 12 h 24 h 24 h Fig. 2. Effect of 1-MCP on the numer of dys t 2 C (fter 18 d of cold storge t 1 C) needed y Hywrd kiwifruit to rech flesh firmness 1 N. During cold storge, () ir ws continuously renovted (1 L/min) to prevent exposure of the fruit to ethylene; () fruit ws exposed to 1. µl L -1 ethylene with flux of 1 L/min. Numer of dys to rech flesh firmness 1 N ws clculted from the verge of ten replictes. 626