Proteins in rice grains influence cooking properties

The Australian rice industry is small compared to others. In order to compete, the industry targets the high-quality end of niche markets. To maintain quality it is important to understand quality attributes and to extract the most information from tests to evaluate quality. Viscosity of the flour (RVA) is a useful tool for evaluating quality. The aim of this study is to determine the effect of proteins on forming a viscosity curve, and then to understand how proteins affect the quality of cooked rice. The results demonstrate clearly that proteins influence viscosity curves both through binding water, which increases the concentration of the dispersed and viscous phase of gelatinised starch and through the agency of a network linked by disulphide bonds. Increasing rates of N nutrition decreases the peak height, consistent with fewer disulphide bonds so less contribution from the linked network. Storage also decreases peak height by increasing disulphide bonds. Proteins affect the amount of water the rice absorbs early in cooking, and the availability of water early in cooking will determine the hydration of the protein and the concentration of the dispersed and viscous phases of the starch, which will determine the texture of the cooked rice. (C) 2002 Elsevier Science Ltd. All rights reserved.