Effects of harvest date and low-temperature conditioning on chilling tolerance of 'Wonderful' pomegranate fruit

摘要

The optimal storage temperatures far 'Wonderful' pomegranates are between 5 and 7.5 degrees C. However, application of a cold-quarantine disinfestation treatment against the Mediterranean fruit fly (Ceratitus capitate) requires exposure to a much lower temperature - below 1 degrees C - for at least 14 days; conditions that often cause chilling injury (CI) symptoms, manifested in surface pitting and internal browning of the white spongy tissue and inner membranes. We demonstrated that harvest time had a remarkable effect on fruit chilling tolerance: early-harvested fruits were very susceptible to CI and were severely damaged after 4 weeks of exposure to 1 degrees C followed by an additional week at a shelf-life temperature of 20 degrees C, whereas late-harvested fruits were rather chilling tolerant and showed. hardly any CI symptoms after similar exposure. In addition, we developed a postharvest low-temperature-conditioning (LTC) treatment for 'Wonderful' ponieg-ranate fruits; it involves exposure to a moderate temperature of 15 degrees C for 10 days before transfer to the cold-quarantine treatment. When this proposed LTC treatment was applied to mid-eason fruits, it entirely prevented the appearance of CI symptoms after 4 weeks storage at 1 degrees C followed by one additional week at 20 degrees C, without impairment of fruit-quality parameters, as manifested in loss of weight, flavor, juice total soluble solids and acid contents, and total antioxidant activity. Overall, these findings demonstrate that harvesting mid- and, preferably, late-season fruits, and applying a pre-storage LTC treatment at 15 degrees C for 10 days, enables export of 'Wonderful' pomegranates to new markets that require cold-quarantine disinfestation treatments against the Mediterranean fruit fly. (C) 2016 Elsevier B.V. All rights reserved.