Effect of Alkaline-Soluble Proteins on Pasting Properties of Nonwaxy Rice Flour

The pasting properties of rice flours and reconstituted rice flours from mixing a common starch with proteins extracted from different rice cultivars at different total protein content levels were studied. Results showed that not only the total protein content but also the protein composition had an effect on the pasting properties of the rice flours. Among the different strands of rice proteins, globulin had the strongest influence on the pasting properties, followed by glutelin, whereas prolamin had the least influence. At the subunit level of the proteins, proteins with a molecular weight of 17,000, most likely from globulin, had the strongest effect on the peak viscosity of the rice flour, followed by those of 33,000. In comparison with that of the rice starch, the influence of proteins in rice was limited. The effect of interactions between the rice proteins and the starch, such as the role of starch-granule-associated proteins, was not isolated in this study, and further investigation is required to quantify this effect.