Response surface optimization and characteristics of Indica rice starch-based fat substitute prepared by α-amylase

Response surface methodology (RSM) was used to study the effect of enzyme to substrate ratio (11.8–23.6 U α-amylase/g rice starch), hydrolysis temperature (90–100°C) and pH value (6.0–6.6) on the gel strength of rice starches-based fat substitute using α-amylase hydrolysis. The optimum conditions obtained from response surface analysis was 16.52 U/g enzyme dosage, 92°C hydrolysis temperature while the influence of pH was found insignificant in the range tested. Under these optimum conditions, the gel strength of this fat substitute was 113 g/cm2, very close to the gel strength of butter of 114 g/cm2, while the solubility of the substitute was 1.33 ± 0.01% and the swelling power 4.85 ± 0.02. There were no observable differences in the granular size distribution between the untreated rice starch and the hydrolyzed rice starch. Rheological properties of this rice starch-based fat substitute implied that it is easier for the substitute to form three-dimensional networks under 34°C.