Studies on the Flesh Quality of Fruit and Vegetables

II. Relation between the Pulp Quality and Properties of Pectic Substances during Post-harvest Ripening of Peaches

Abstract

This work was undertaken to clarify the relation between the pulp quality and properties of pectic substances during ripening after the harvest of peaches. The varieties studied were white-pulp peaches (Kurakata-wase and Okubo) and yellow-pulp peaches (Kanto No.2, No.5, and No.14).
The firmness of the Okubo-type decreased markedly during ripening. It became noticeable after only three day′s ripening after harvest. In the case of the yellow varieties, the firmness decreased gradually during ten day′s ripening.
In white varieties, water-soluble pectin increased remarkably with advancing ripeness, reaching about 50% or more after four day′s ripening. In the yellow varieties, the pectin level was considerably lower than in white varieties. The decrease in pulp firmness was found to be closely related to both the increase in the proportion of watersoluble pectin and to the decrease in the proportion of hydrochloric acid-soluble pectin with advancing ripeness.
The properties of crude pectins isolated from alcohol insoluble solids were as follows. In the water-soluble pectin of the Okubo-type, a continuous decrease in the uronic acid and methyl ester content, and a continuous increase in the hexose (determined as glucose) in the pectic substance were found to occur as ripening progressed. However, pectins from the yellow varieties do not exhibit this behavior. The intrinsic viscosity of both water- and acid-soluble pectin from Okubo-type decreased rapidly with advancing ripeness. The pectic substances from yellow varieties do not exhibit such a decreasing pattern.