Effects of potassium sulfate on swelling, gelatinizing and pasting properties of three rice starches from different sources

This study evaluates the effects of potassium sulfate (K₂SO₄) on the swelling, gelatinization, and pasting properties of indica rice starch (IRS), japonica rice starch (JRS), and waxy rice starch (WRS). As a result, the gelatinization temperatures (T_p), swelling capacities, and pasting viscosities of rice starches in water followed the order of WRS > JRS > IRS, showing positive correlations to amylopectin content and molecular weight. At K₂SO₄ concentration of 0.05-0.6 M, T_p increased by 10-13 ℃ due to a more compact structure of starch granules resulting from increased interactions of starch chains with K⁺. However, the swelling capacity decreased with increasing K₂SO₄ concentration and followed the order of WRS < JRS < IRS, which decreased sharply from 27.3 to 2.5 g/g for WRS. K₂SO₄ dramatically reduced the pasting viscosity of starch pastes due to the decreased swelling capacity. This study provides the scientific basis for rice starch processing with K₂SO₄.