Structural changes in polysaccharides isolated from chestnut (Castanea mollissima Bl.) fruit at different degrees of hardening

Hardening is an important physiological disorder of chestnut fruit during storage. In this study, polysaccharides of chestnut (PCs) at 0%, 50% and 100% degrees of hardening (DH) were extracted and then sequentially fractionated using 40% and 80% ethanol in order to obtain PCs I and II. For fresh chestnut, arabinose, fructose, glucose and galactose were the main monosaccharides of PCs I and II. Significantly positive correlations (P < 0.01) existed between xylose, galactose, arabinose contents and DH, while significantly negative correlations (P < 0.01) were present between glucose, fructose contents and DH for both PCs I and II. The appearance in hardening of chestnut fruit was accompanied with decreases in the contents of 1,3-fructose, 1,3- and 1,6-glucose, and increases of 1,4-arabinose, 1,6-galactose and 1,3-xylose. The results confirmed that cell wall degradation of chestnut induced the structural changes in PCs I and II, which further led to the occurrence of hardening.