The effect of rice aging on the freeze–thaw stability of rice flour gels

Abstract

This study investigated the effect of aging rice on the freeze–thaw stability of rice flour gels since repeated freeze–thaw cycles can lead to reduced food quality. A rice grain cultivar called ‘Khoa Dawk Mali 105’ was aged for three different time periods, ranging from 0 to 12 months. Rice gels made from the aged rice were then freeze–thawed for up to 5 cycles. Repeated freeze–thaw cycles lead to an increase in syneresis values and hardness with increasing rice aging. Differential scanning calorimetry showed an increase in the enthalpy of melting of the amylose–lipid complex after 5 freeze–thaw cycles and an increase in peak gelatinization temperature and gelatinization enthalpy with longer rice aging. Moreover, aging length of the rice correlated significantly with a decrease in peak viscosity and breakdown but also an increase in final viscosity and setback. These results demonstrate that aging the rice reduced the freeze–thaw stability of the rice flour gels.