Developing Optiml Controlled Atmosphere Conditions for Thompson Seedless Tle Grpes C.H. Crisosto, D. Grner, nd G. Crisosto Deprtment of Pomology University of Cliforni, Dvis, t Kerney Agriculturl Center 924 South Riverend Ave., Prlier, CA 93648 USA Keywords: rchis rowning, Vitis vinifer, SO 2 lterntive, mturity, storge potentil, erry rowning Astrct Efficcy of controlled tmosphere (CA) conditions for decy control in Thompson Seedless tle grpes ws evluted. Erly (16.5% solule solids content = SSC) nd lte hrvested (19% SSC) grpes were exposed to 5, 1, 15, nd 25% CO 2 comined with 3, 6 nd 12% O 2. Grpes were initilly SO 2 fumigted nd ir stored grpes were used s controls. Storge tmospheres did not ffect SSC, TA, SSC:TA, or erry shtter. The min storge limittions for erly hrvested Thompson Seedless tle grpes were rchis nd erry rowning development, which resulted from exposure to >1% CO 2. However, >15% CO 2 ws needed to control totl decy nd nesting development independent of O 2 concentrtions. CA ws more effective in decy control without detrimentl effects on qulity when lte hrvested grpes were used. The comintion of 15% CO 2 with 3, 6 or 12% O 2 is suggested for up to 12 weeks storge only for lte hrvested Thompson Seedless tle grpes; CA should not e used for erly commercilly hrvested grpes. INTRODUCTION The most importnt tle grpe cultivr worldwide is Thompson Seedless nd it is mrketed nerly yer round throughout the world. For exmple, in, Cliforni produced pproximtely 224 metric tons, nd in 1, Chile produced pproximtely 176 metric tons. Controlled tmospheres (CA) including elevted CO 2 concentrtions hve een shown to control decy development on some commodities without ffecting qulity ttriutes during trnsport nd/or storge. Few studies hve een done on Thompson Seedless (Berry nd Aked, 1997; Nelson, 1969; Yhi et l., 1983). Nelson (1969) found tht erry internl rowning incidence overcme the potentil enefits of CA in his erly trils with Thompson Seedless tle grpes from the Cochell Vlley. Yhi et l. (1983) using 5% CO 2 + 2% O 2, reported tht decy nd erry internl rowning development were the min deteriortion symptoms noted eyond eight weeks storge. In reserch crried out in Englnd with Thompson Seedless tle grpes from Egypt, Berry nd Aked (1997) oserved n inhiition of Botrytis cinere y exposure to CA of 15% CO 2 + 5% O 2. Our ojective ws to determine optiml CO 2 nd O 2 levels to control gry mold (Botrytis cinere) without ffecting qulity ttriutes of Thompson Seedless tle grpes. MATERIALS AND METHODS During the 1998 seson, Thompson Seedless tle grpes were hrvested ccording to their solule solids content (SSC) t erly (16.5%) nd lte (19%) commercil mturity. Grpe smples were stored under 16 CA comintions for up to 12 weeks t ºC. The 16 CA comintions were 5, 1, 15,, nd 25% CO 2 comined with 3, 6, nd 12% O 2. Air storge ws used s control for ll of the tretments. Flow rtes nd gs mixtures were estlished using mixing ord with micro-metering vlves. Supply nd exhust gs O 2 nd CO 2 composition ws monitored using n Ametek prmgnetic oxygen nlyzer (S-3A/II) nd Hori infrred gs nlyzer (VIA-51 for Proc. 8 th Int. CA Conference Eds. J. Oosterhven & H.W. Peppelenos Act Hort 6, ISHS 3 817
CO 2 ). Five clusters (replictions) per tretment were removed every four weeks for qulity evlutions, including solule solids concentrtion (SSC), titrtle cidity (TA), SSC:TA, rchis rowning, erry shtter, skin nd erry rowning, nd otrytis development. Rchis rowning (stem rowning) development ws evluted using the following sujective scoring system s descried y Crisosto et l., 1. All rown erries were removed nd weighed, nd erry rowning ws expressed s percentge of cluster weight. Botrytis decy ws evluted s nesting formtion nd totl decy. Numer of nests ws then counted for ech cluster. Totl decy ws clculted y weighing helthy erries. Then, decyed erry weight ws clculted y sutrcting totl cluster weight minus the weight of the helthy erries. Thus, totl decy ws expressed s percentge of decyed erries sed on the originl cluster weight. We used fctoril design, using CO 2 nd O 2 levels s fctors, with three replictions. The dt were sujected to nlysis of vrince (ANOVA) prior to Lest Significnt Differences (LSD) mens seprtion using the SAS progrm. The SAS sttisticl softwre (SAS Institute, Cry, NC) ws used for these nlyses. RESULTS AND DISCUSSION High CO 2 tretment suppressed gry mold growth on erly (16.5% SSC) nd lte (18.% SSC) hrvested Thompson Seedless tle grpes. Nturl quiescent otrytis infection rnged from none to 5.5% in the first month for ir stored erly hrvested grpes. For lte hrvested grpes, nturl otrytis infection vried from 1. to 32.8%. In ll cses, decy incidence ws not relted to O 2 or the O 2 -CO 2 interction. Since otrytis ws only ffected y CO 2 concentrtions, ANOVA nd LSD nlysis were crried out including ir tretment nd CO 2 tretments. For oth erly nd lte mturity grpes, otrytis development ws not visile until the second month of storge, when it ws significntly higher on the ir stored grpes thn ny of the CO 2 storge tretments. In ll of the cses, otrytis incidence ws significntly reduced when CO 2 concentrtions were >15% during storge (Fig. 1). There were no significnt differences in decy control etween the 1% to 25% CO 2 tretments, except under high Botrytis pressure tht occurred in the lte hrvested grpes. Similr results were reported for Monilini fructicol on sweet cherries (Tin et l., 1). For erly nd lte hrvested grpes, the CO 2 nd O 2 comintions tested did not significntly ffect erry shtter, SSC, TA or SSC:TA (dt not shown). Air stored erly nd lte hrvested grpes did not develop commercilly importnt erry rowning even fter 9 dys storge. However, erry rowning lwys incresed on erly hrvested grpes under ny of the CA tretments (Fig. 2). Berry rowning ws ccelerted y >15% CO 2 fter 6 dys in storge. No or very slight erry rowning ws oserved on lte hrvested (19% SSC) grpes, except those exposed to 25% CO 2, which exhiited out 11% erry rowning fter 6 dys in storge. In oth mturity stges, the O 2 nd CO 2 interction ws not relted to the onset of rchis rowning. Rchis rowning development ws significntly lower on the ir-stored grpes thn on grpes from ny of the CO 2 storge tretments (dt not shown). For erly hrvested grpes, rchis rowning ecme commercilly importnt (score >2.) y the first month. Lte hrvested grpes tolerted high CO 2 very well. Only lte hrvested grpes stored under >% CO 2 strted to show the first signs of rchis rowning. After two months storge, the <15% CO 2 tretment did not ffect rchis rowning of lte hrvested grpes during two months storge (dt not shown). For erly hrvested grpes, the use of >1% CO 2 significntly incresed rchis rowning within one month in storge (Tle 1). On grpes stored under >1% CO 2 the rchises hd slight rowning fter two months storge. After three months, >1% CO 2 significntly ccelerted rchis rowning turning the rchis completely rown. 818
CONCLUSIONS Bsed on our work, >15% CO 2 is necessry to control Botrytis decy on Thompson Seedless tle grpes. However, grpe qulity losses such s rchis nd erry rowning development were induced on erly hrvested grpes. Becuse of these potentil qulity prolems we do not recommend the use of CA for erly hrvested Thompson Seedless tle grpes. For our work, we defined erly hrvested grpes s those with out 16% SSC nd lte hrvested grpes s those nering % SSC. Since lte hrvested Thompson Seedless tle grpes tolerte 15% CO 2 very well, we suggest CA of 15% CO 2 comined with 3, 6 or 12% O 2 to limit Botrytis development without dversely ffecting qulity ttriutes. Literture Cited Berry, G. nd Aked, J. 1997. Controlled tmosphere lterntives to the posthrvest use of sulfur dioxide to inhiit the development of Botrytis cinere in tle grpes. CA 97 Proc., Vol. 3, Posthrvest Horticulture Series No. 17. Posthrvest Outrech Progrm, University of Cliforni, Dvis, p. 1. Crisosto, C.H., Smilnick, J.L. nd Dokoozlin, N.K. 1. Tle grpes suffer wter loss, stem rowning during cooling delys. Cliforni Agriculture 55(1):39-42. Kder, A. 1997. A summry of CA nd MAP requirements nd recommendtions for fruit other thn pples nd pers. CA 97 Proc., Vol. 3, Posthrvest Horticulture Series No. 17. Posthrvest Outrech Progrm, University of Cliforni, Dvis, p. 14. Nelson, K.E. 1969. Controlled tmosphere storge of tle grpes. Proc. Ntl. CA Res. Conf., Michign Stte Univ., Hort. Rpt. 9: 69-7. Tin, S., Fn, Q., Xu, Y., Wng,F. nd Jing, A., 1. Evlution of the use of high CO 2 concentrtions nd cold storge to control Monilini fructicol on sweet cherries. Posthrvest Biol. Technol. 22: 53-6. Yhi, E.M., Nelson, K.E. nd Kder, A.A. 1983. Posthrvest qulity nd storge life of grpes s influenced y dding cron monoxide to ir or controlled tmospheres. J. Amer. Soc. Hort. Sci. 18: 167-171. Tles Tle 1. Effect of CO 2 nd O 2 concentrtions on rchis rowning of erly hrvested (16.5% SSC) Thompson Seedless tle grpes during cold storge, 1998. Rchis rowning score (1-4) Storge time Tretment 1 month 2 months 3 months CO 2 concentrtion (%) 5 1.3 1.4 2. 1 1.2 2. 3.1 15 2.2 2.2 3.7c 2.7c 3.9c 4.c 25 2.9c 4.c 4.c P vlue.1.1.1 LSD.5%.6.5.6 O 2 concentrtion (%) 3 2.1 2.7 3.3 6 2.4 2.7 3.5 12 1.7 2.7 3.3 P vlue.35.93.63 LSD.5%.5 NS NS CO 2 x O 2 P vlue NS (.5).29 NS (.48) 819
4 3 Erly 'Thompson p =.3 Lte 'Thompson p =.15 1 DECAY (% cluster wt.) 4 3 1 p =.4 c p <.1 d d d 4 3 Month 3 p <.1 5 1 15 25 1 5 1 15 25 STORAGE ATMOSPHERE (% CO 2 ) Fig. 1. Decyed erries, expressed s percentge of cluster fresh weight, of erly (16.5% SSC) nd lte (19% SSC) hrvested Thompson Seedless tle grpes fter 1, 2, nd 3 months storge in different CO 2 -enriched tmospheres. Different letters indicte significnt difference etween storge tmospheres y LSD.5. 8
Erly 'Thompson Lte 'Thompson 1 8 p =.1 p =.53 6 4 BROWN BERRIES (%) 1 8 6 4 1 8 p =.12 Month 3 p <.1 p =.16 5 1 15 25 6 4 c c 5 1 15 25 STORAGE ATMOSPHERE (% CO 2 ) Fig. 2. Brown erries, expressed s percentge of cluster fresh weight, of erly (16.5% SSC) nd lte (19% SSC) Thompson Seedless tle grpes fter 1, 2, nd 3 months storge in different CO 2 -enriched tmospheres. Different letters indicte significnt difference etween storge tmospheres y LSD.5. 821