Changes in pectic substances during the ripening of strawberry fruit

Abstract

This paper dealt with the relationship between softness of fruits and changes of pectic substances during the ripening of strawberry fruit "Hokouwase". Four pectin fractions were separated by sequential extraction from AIS into WP with water, PP with hexametaphosphate, HP with hydrochloric acid and KP with potassium hydroxide. The results obtained were as follows. 1) The total amount of galacturonic acid in four separated pectin fractions decreased with ripening of strawberry fruits. 2) WP which was little in immature stage increased with maturation. On the other hand, HP which was the most abundant in immature stage decreased to the same amount of WP at a ripe stage. 3) WP, PP and HP were the high-methoxyl pectins throughout the maturation. 4) The molecular weights of four separated pectin fractions were estimated by Cellulofine gel permeation chromatography, that is, WP, PP had 1 000 000, HP had 300 000 and KP had 10 000 in immature stage. However these molecular weights were tend to lower with the maturation. Especially, the molecular weight of HP was lowered to 250 000 in a greenish-white stage and to 100 000 in a ripe stage.