Formation of Hard Gel from a Thick Amylopectin Paste

Mechanical Properties of Waxy Rice Cake, Mochi Part VIII

Abstract

r 20min. The paste, at concentrations ranging from 5 to 20%, changed into a turbid sol after storage at a temperature below 5°C for 3 days. There was a linear relationship between log G' and log C². However, an amylopectin sol formed a hard gel at aconcentration above 20%, and G' increased rapidly in proportion to C¹⁷. Since the almost same values of G' for waxy corn starch were obtained as those for Shiratama mochi cake even at low concentration, it was suggested that amylopectin molecules might contribute to the establishment of hardness in the latter as in the former paste. The formation of hard gel for waxy corn starch depended on period of storage at a low temperature. A hyperbolicrelationship between the setting time and the concentration of waxy corn starch was observed. It was revealed by phase microscopic observation that an increase of turbidity of the paste of waxy corn starch might be due to the development of micro-granules, that a phase-separated networks between the molecules might be involved.