PHOSPHOLIPID, GALACTOLIPID, AND STERYL LIPID-COMPOSITION OF APPLE FRUIT CORTICAL TISSUE FOLLOWING POSTHARVEST CACL2 INFILTRATION

Fruit firmness and membrane lipid composition were evaluated in outer cortical tissue of 'Golden Delicious' apples, which were pressure-infiltrated with distilled water, or 2 or 4% CaCl2 solutions at harvest. After six months storage at 0 degrees, fruit were held at 20 degrees for 1, 7 or 14 days and then evaluated. During storage at 0 degrees, firmness had decreased by 20% in water-infiltrated fruit, but by only 6% in fruit infiltrated with 4% CaCl2. During the span of 7 to 14 days at 20 degrees, firmness decreased more rapidly in water-infiltrated fruit compared with CaCl2-infiltrated fruit. Reductions in specific phospholipids (primarily phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol) occurred after transfer to 20 degrees but were largely independent of the infiltration treatment. Steryl glycosides, acylated steryl glycosides, monogalactosyldiacylglycerol and digalactosyldiacylglycerol concentrations were positively correlated to CaCl2 concentration of infiltration solutions, and a large, transient increase (35-37%) in acylated steryl glycoside concentration occurred during the first 7 days at 20 degrees in CaCl2-infiltrated fruit. In contrast, acylated steryl glycosides decreased by 19% in water-infiltrated fruit over the same time interval. Overall, the results indicate that CaCl2 infiltration may delay galactolipid breakdown, increase the rate of sterol conjugation, and thus affect membrane organization and function during postharvest life of apple fruit.