EFFECTS OF HEAT-TREATMENT ON PLASMA-MEMBRANE OF APPLE FRUIT

Apple fruits (Golden Delicious) were held at 20 or 38 degrees C for fo ur days prior to storage at 0 degrees C for five months. Plasma membra ne composition and function were examined before and after storage. Wh ile fruits were held at 38 degrees C, membrane microviscosity and ster ol content increased, phospholipid fatty acids became more saturated a nd there was increased electrolyte leakage from apple fruit discs. ATP ase activity increased during the first day of heating and decreased t hereafter. After five months of storage at 0 degrees C, microviscosity and leakage were lower in heated fruit, and increased more slowly dur ing ripening at 20 degrees C than in control apples. ATPase activity w as similar in both treatments. Phospholipid content was higher in memb ranes from heated apples than in those from control fruit. Although fa tty acid content in apples from both treatments was similar after stor age, the loss of unsaturated fatty acids during ripening occurred more rapidly in control apples. Heated apples recovered rapidly from stres s and acclimated more successfully to 0 degrees C than did control app les.