Effect of Water Content on Rice Starch Gel during Retrogradation

Abstract

Water content plays a crucial role in the retrogradation of rice starch. The relationship between the water content of rice starch gels and their structural changes during retrogradation is studied. The results indicate that the gels have three distinct types of water: structural constitution water, starch intermolecular bound water, and free water. The rate of retrogradation increases as the water content increases. Nevertheless, when the water content is lower (1:1) or higher (1:6) than optimal, the starch molecules show limited aggregation and recrystallization, which retards the rate of retrogradation. With the aggregation and recrystallization of starch and the inward contraction of the gel structure, the mobility of water is restricted, and the binding of water to the starch is enhanced. With the sustained contraction of the gel structure, the water‐holding capacity of the gel is weakened. By analyzing the experimental results, water distribution, transformation, and migration in rice starch during retrogradation are delineated. These findings provide a theoretical basis for controlling the retrogradation of rice starch and improving product quality.