Whitaker, B.D., USDA-ARS Hort. Crops Qual. Lab., BARC-West, Beltsville, MD 20705, United States
Klein, J.D., Agricultural Research Organisation, Volcani Center, Bet Dagen 50250, Israel
Conway, W.S., USDA-ARS Hort. Crops Qual. Lab., BARC-West, Beltsville, MD 20705, United States
Sams, C.E., Department of Plant and Soil Science, University of Tennessee, Knoxville, TN 37901, United States

Heating 'Golden Delicious' apples for 4 days at 38°and/or pressure infiltrating the fruit with a CaCl2 solution after harvest, maintains firmness and reduces decay during storage. The possibility that these beneficial effects involve changes in membrane lipid metabolism was investigated. Lipids of hypodermal cortical tissue were analyzed after 0, 1, 2 or 4 days at 38°and after storage (15 weeks at 0°plus 1 week at 20°) of fruit that were untreated (Ctl), heated 4 days at 38°(HT), infiltrated with 2% CaCl2 (Ca) or heated then infiltrated (HT+Ca) before storage. Overall, effects of liT were much more pronounced than those of Ca and effects of HT + Ca were intermediate between those of HT or Ca alone. An initial phase of membrane damage induced by heating, indicated by glycerolipid loss over the first 1-2 days, could explain why HT for less than 3-4 days has an adverse effect on post-storage quality. HT effects on plastids, including accelerated chlorophyll and monogalactolipid loss, as well as carotenoid accumulation, are likely to cause the distinct yellowing of the fruit. HT-induced reductions in steryl glycosides and cerebrosides prior to storage similar to those that occurred in Ctl and Ca fruit during storage, and the phospholipid (PL) content of HT fruit after storage was close to that of Ctl fruit at harvest. Also, the ratio of linoleate to oleate in PL was much higher in HT and HT+Ca than in Ctl fruit at the end of storage. One or more of these effects of HT on membrane lipids could be involved in the ultimate benefits to fruit quality. Published by Elsevier Science Ltd.