Changes in Structural, Physicochemical, and Digestive Properties of Chinese Wild Rice Starch before and after Heat-moisture Treatment
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Abstract:
Here, the effects of heat-moisture treatment (HMT) on the structural, physicochemical, and digestive properties of Chinese wild rice starches with different moisture contents (HMT-15, HMT-20, HMT-25, HMT-30) were investigated. Results showed that under conditions of HMT, the morphology of starch granules in wild rice was damaged to varying degrees, the crystalline structure of starch was altered, and short-range ordering was reduced; these phenomena became more pronounced as the moisture content of the system increased. The particle size of starch increased from 0.84 μm to 5.14 μm, and the relative crystallinity of starch decreased from 26.29% to 20.65%. The solubility of starch derived from Chinese wild rice increased from 19.25% to 24.01%, and the swelling degree decreased from 15.13 g/g to 12.11 g/g. The freeze-thaw stability of this starch tended to first increase and then decrease. The syneresis rate of HMT-20 (35.12%) was the highest, while that of HMT-30 (13.12%) was the lowest (significantly lower than even that of natural wild rice starch (19.66%)). Analysis of the gelatinization properties showed that HMT increased the gelatinization temperature of wild rice starch and reduced the viscosity and retrogradation of the wild rice paste system. In vitro digestion showed that in Chinese wild rice starch, the content of rapidly digestible starch (RDS) decreased significantly, while that of resistant starch (RS) increased significantly with increasing moisture content in the system; HMT-30 had the lowest RDS content (20.49%) and the highest RS content (28.66%). Chinese wild rice starch exposed to HMT under conditions of high moisture exhibited robust stability in both hot and cold conditions, and good aging resistance and digestive resistance. The results of this study would provide new ideas for the further processing and promotion of Chinese wild rice starch.
