Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2006
Publication Date: 9/5/2006
Citation: Defilippi, B.G., Whitaker, B.D., Hess-Pierce, B.M., Kader, A.A. 2006. Development and control of scald on wonderful pomegranates during long-term storage. Postharvest Biology and Technology. 41:234-243. Interpretive Summary: A disorder in pomegranates called scald, which appears as sunken brown patches on the fruit surface, is one of the major factors limiting their storage life. Scald also makes the pomegranates more prone to fungal decay, resulting in additional losses after storage. This study was conducted to determine which treatments and storage conditions are best to prevent scald. Since scald is also a serious problem in some varieties of apple fruit, two treatments known to be effective in controlling apple scald were tested. Pre-storage treatments were largely ineffective, indicating that the biochemical mechanism involved in scald development is different in pomegranate and apple fruits. This work established optimal conditions for pomegranate storage that can be adopted by fresh fruit distributors and wholesalers to reduce losses and extend storage life. It also provided information that will be useful to plant scientists trying to elucidate the biochemical basis of scald development in pomegranate.
Technical Abstract: Scald incidence and severity were greater on pomegranates harvested during late season than on those harvested during mid season, indicating that this disorder may be associated with senescence. All pomegranates from both harvests that were kept in air exhibited some scald after 4 to 6 months at 7C. Neither diphenylamine (DPA) nor 1-methylcyclopropene (1-MCP) alone or together reduced scald incidence and severity. In contrast, the three controlled atmosphere (CA) storage conditions tested significantly reduced scald incidence and severity on pomegranates from both harvest dates for up to 6 months at 7C. However, the two CA treatments with 1% oxygen resulted in greater accumulation of fermentative volatiles (acetaldehyde, ethanol, and ethyl acetate) than the CA treatment with 5% oxygen, especially in the mid-season-harvested pomegranates. In addition to its fungistatic effects, 15% carbon dioxide appears to be critical for inhibition of scald development on pomegranates. These results confirm our recommendation of 5% oxygen + 15% carbon dioxide as the optimal CA for pomegranates at 7C and 90-95% relative humidity. Since very little if any alpha-farnesene or its conjugated trienol oxidation products were found in the peel of pomegranates, it appears that the biochemical basis of scald in pomegranates is different from that in apples. CA storage delayed or prevented biochemical changes associated with scald development in stem-end peel tissue of air-stored fruit, including increases in carotenoids, non-polar acyl lipids, and lipophilic p-coumaric acid conjugates. We are examining the possible involvement of reactive oxygen species, free radicals, and fatty acid oxidation in the development of scald on pomegranate skin.