Effect of Storage Time and Storage Protein on Pasting Properties of Khao Dawk Mali 105 Rice Flour

Abstract

Aging significantly affected the solubility of storage proteins and pasting properties of Khao Dawk Mali 105 rice flour. The protein solubility of rice from freshly harvested and seven-month stored rice differed significantly. The freshly harvested rice showed higher protein content (5.35 g%), whereas the storage rice showed lower protein content (4.29 g%). The protein component of rice flour from nonstored and stored rice mainly consisted of glutelin, with values of 3.86 g% and 3.09 g%, respectively. The rice flour from non-stored rice consisted of 1.00 g% globulin, 0.25% albumin and 0.23% prolamin and the rice flour from stored rice consisted of 0.74 g% globulin, 0.12% albumin and 0.34% prolamin. Aging significantly increased the pasting viscosity of rice flour, but decreased the protein solubility. Peak viscosity of non-stored rice flour decreased by 24% in dealbumin rice, by 44% in deglobulin rice and by 3% in deprolamin rice, but increased 15% in deglutelin rice. Storage might lead to a protein matrix more closely associated with the starch granules and this could explain the changes observed in the solubility and pasting properties.