Cross-linking Denaturation Reaction of Amaranth Starch and the Physicochemical Properties of Its Products

To investigate the cross-linking denaturation reaction characteristics of very small granular starch and the physicochemical properties of the products with different degrees of substitution, in this study, the effects of temperature (45, 50, 55 ℃), pH (9.0, 10.0, 11.0) and expansion inhibitor Na₂SO₄ concentration (5%, 10%, 15%) on the process and efficiency of the cross-linking reaction were investigated and physicochemical properties of the cross-linking products with different degrees of substitution (DS) were compared using amaranth starch as raw material, sodium trimetaphosphate as denaturant and waxy corn starch (WCS) as control. The results showed that the cross-linking reaction of AS was less influenced by temperature compared to WCS, and it was difficult to increase the efficiency of the cross-linking reaction by simply increasing the temperature. On the contrary, both pH and Na₂SO₄ concentration promoted the cross-linking denaturation reaction of AS and WCS, and higher pH levels (10.0~11.0) and Na₂SO₄ concentrations (5%~15%) led to faster rates of cross-linking reaction. The viscosity of low-substitution cross-linked AS (DS 0.1×10⁻³~0.8×10⁻³) after pasting was greater than 50 cP with a stable thickening effect; high-substitution cross-linked AS (DS≥0.8×10⁻³) exhibited a viscosity below 50 cP after pasting, with a weak thickening ability and a fat-like appearance and texture. This study showed that pH and the concentration of expansion inhibitor Na₂SO₄ were effective means of regulating the reaction rate of amaranth starch, and that cross-linked amaranth starch had a weak thickening ability but good viscosity stability and shear resistance, which was potentially valuable in its application as a fat substitute.