Effect of the Degree of Enzymatic Hydrolysis on the Physicochemical Properties and in vitro Digestibility of Rice Starch

Abstract

Rice starch was subjected to enzymatic treatment with pullulanase and the physicochemical properties of the modified rice starch were investigated as a function of the degree of hydrolysis which ranged from 0.9 to 10.2%. The enzymatic hydrolysis of rice starch caused a decrease in the fraction of rapidly digestible starch (RDS) (78.31 -> 44.65%), whereas the levels of slowly digestible starch (SDS) (0.8 -> 22.18%) and resistant starch (RS) (20.79 -> 34.43%) increased, consequently reducing in vitro starch digestibility. In addition, the swelling factor of rice starch decreased with increasing enzyme concentration while an increase in its syneresis was observed. In rapid visco analyser (RVA) measurement, dramatic decreases in the peak viscosity (452.5 -> 12.0 cp), breakdown (307.0 -> 4.5 cp), and setback (207.0 -> 3.0 cp) were observed in the enzyme-treated rice starch of which X-ray diffraction showed that there was the coexistence of A-and V-type crystallinity.