Effects of water loss of 'Fuyu' persimmon fruit on molecular weights of mesocarp cell wall polysaccharides and fruit softening

Distributions of molecular weights of cell wall fractions of persimmon 'Fuyu' fruit (Diospyros kaki Thunb.), stored under low and high humidities, were measured. The molecular weight of total sugar of water-soluble (WS) polysaccharides from alcohol-insoluble solids under both low and high humidities shifted to lower molecular mass during storage. The amount of larger sized polymers in fruits kept at low humidity was less than that at high humidity during late stage of storage. Weight-average molecular weights of pectic polysaccharides under high humidity were higher than that under low humidity condition. Coefficient between fruit firmness and the level of individual polysaccharides was higher than those between fruit firmness and weight-average molecular weight of WS, pectin or hemicellulose fraction. These results were confirmed by multiple regression analysis. Hence, fruit firmness of persimmon mesocarp is not influenced by changes in a single cell wall fraction but by all cell wall fractions, i. e., the content of cell wall polysaccharides plays a grater role in determining fruit firmness than do their molecular weights.