Cereal Chem. 70:377-380   |  VIEW ARTICLE

Effect of Disulfide Bond-Containing Protein on Rice Starch Gelatinization and Pasting.

B. R. Hamaker and V. K. Griffin. Copyright 1993 by the American Association of Cereal Chemists, Inc. 

Flours from short, medium, and long grain rice varieties were analyzed for viscosity, gel consistency, and degree of gelatinization, with and without treatment with dithiothreitol or 2-mercaptoethanol, to examine the effect of endosperm protein containing intermolecular disulfide bonds on pasting characteristics of rice flour. When flour slurries were cooked under negligible shear stress and measurements were made under low-shear conditions, viscosity and gel consistency increased in the presence of a reducing agent. When protein disulfide bonds are disrupted, rice starch granules apparently swell to a larger size, thereby increasing viscosity. However, viscosity decreased when the reducing agent was added before cooking and only moderate shear stress was applied. This indicated that the swollen granules were more fragile in the presence of a reducing agent. Degree of gelatinization was lower in flours of the long grain nonst icky rices, and it increased following treatment with 2-mercaptoethanol. Proteins with disulfide bonds in the rice flour restrict starch granule swelling during gelatinization and make the swollen granules less susceptible to disruption by shear.