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2013 ASHS Annual Conference

14657:
Chlorine Dioxide Sachets for the Control of Postharvest Decay of 'Crimson Seedless' Table Grapes

Tuesday, July 23, 2013
Desert Ballroom: Salons 7-8 (Desert Springs J.W Marriott Resort )
Xiaofan Zhao, California State University, Fresno, Fresno, CA
Jan Narciso, Citrus and Subtropical Products Research Unit, USDA, ARS, USHRL, Ft. Pierce, FL
Sonet Van Zyl, California State University, Fresno, Fresno, CA
Joseph Smilanick, USDA–ARS, Parlier
Table grapes are of increasing importance in the world. Gray mold (Botrytis cinerea) is the main postharvest decay problem of table grapes and limits their shelf-life. Sulfur dioxide (SO2) is traditionally used as an antimicrobial postharvest, in packages or storage rooms. Concerns about harm to human health from SO2 encourage evaluation of alternatives. Chlorine dioxide (ClO2) has proven effective to control microorganisms on produce. Our objectives were to assess the ability of ClO2 to control rot and influence quality. ClO2 gas was generated inside packages from sachets (2.5 by 4 cm, containing 0.1, 0.2, or 0.3 g CuroxinTM; Worrell Water Technologies, VA). SO2 was generated from sachets (4.5 by 6 cm, containing 0.3 g sodium metabisulfite; OSKU S.A., Chile).  Our first experiment evaluated decay control, while the second evaluated berry quality. Experiment 1—plastic clamshells with 500 g of ‘Crimson Seedless’ berries (6 g/berry) were used. Grapes were inoculated by injection of conidia 0.5 cm deep into berries. One inoculated berry was placed in the center of each clamshell with nothing (control) or one sachet (SO2, 0.1, 0.2, or 0.3 g ClO2).  Clamshells were placed inside an expanded polystyrene box with a plastic liner and stored for: 1) one month at 0 °C; or 2) one month at 0 °C + 1 week at 10 °C. After 1 month, decay incidence in clamshells (control or with SO2, 0.1, 0.2, and 0.3 g ClO2 sachets) was 22.8%, 4.8%, 3.4%, 1.7%, or 0.8%, respectively. After 1 month + 1 week, incidence in control, or SO2, 0.1, 0.2, and 0.3 g ClO2 sachets was 38.3%, 5.4%, 8.2%, 5.5%, or 4.1%, respectively. Natural incidence was similarly reduced. Some rachis injury was observed, particularly with 0.3 g ClO2. SO2 retarded aerial mycelia growth on inoculated berries. ClO2 retarded it after 1 month, but not after 1 month + 1 week. Experiment 2—grapes were prepared as before, without inoculation, with nothing (control) or a sachet (SO2, 0.1 or 0.3 g ClO2), and stored for: 1) 1 week at 0 °C, 2) 1 month at 0 °C, or 3) 1 month at 0 °C + 1 week at 10 °C. Within each period, color (LCh), rachis appearance, shatter, soluble solids, pH, acid content, firmness, and berry size did not differ significantly.  Berry appearance, particularly controls, declined during storage. Unlike experiment one, ClO2 (0.3 g) caused no rachis injury. ClO2 effectively controlled decay with minimal harm to grapes.