Structural features of pectins from fresh and sun-dried Japanese persimmon fruit

Abstract

Softening-associated changes in a cold-water-soluble pectin, CWP3 of Japanese persimmon fruit are investigated by methylation analysis. Methylation analysis showed that rhamnose occurred as (1 → 2)- and (1 → 2,4)-linked residues in CWP3 (from fresh persimmon), newly solubilized CWP3 (fraction ‘a’ from sun-dried persimmon) and depolymerized CWP3 (fraction ‘b’ from sun-dried persimmon) as expected for the presence of ‘hairy’ regions. Solubilization of pectin into CWP3 occurred with higher proportions of (1 → 5)-linked arabinan side-chains and lower proportions of (1 → 3)/(1 → 6)-linked arabinogalactan side-chains compared to the respective side chains in CWP3 (fresh persimmon). During the sun-drying process, marked losses of (1 → 3,6)-linked galactose residues from CWP3 occurred, due to extensive degradation of main-chains of arabinogalactans. This implied losses of both types of sugars, arabinose (as terminal) and galactose from arabinogalactans in CWP3 of Japanese persimmon. During the sun-drying process, the molecular size distribution of CWP3 was affected due to degradation of arabinogalactan and arabinan side-chains.