POSTHARVEST CHANGES OF PECTIC SUBSTANCES IN CHILLED PEACHES

Red Globe peaches were harvested at the threshold-mature stage and either stored at 0C after preripening at 20C for 48 h or stored directly at 2C Total pectin increased from 7.49 mg/g fresh weight in the threshold-mature sample to 10.21 mg/g in pre-ripened fruit stored at 0C and 12.83 mg/g in fruits stored directly at 2C. Depending on extraction and storage protocol, between 26% and 73% of total pectin was solubilized. Chelator-soluble fractions had a low degree of esterification (DE ca. 20%), whereas other fractions were highly methylated (DE ca. 56% to 74%). Average DE did not vary between samples. DEAE-cellulose chromatography revealed an uneven distribution of methoxyl groups. Two prominent peaks were observed in chromatograms of chelator-soluble extracts from threshold-mature fruit and fruit stored directly at 2C. One peak was observed in chelator-soluble pectin from preripened fruit stored at 0C.