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Physicochemical properties and in vitro digestibility of rice after parboiling with heat moisture treatment

Cheng, Kang-Che, Chen, Shih-Hsin, Yeh, An-I.
Journal of cereal science 2019 v.85 pp. 98-104
X-ray diffraction, amylose, differential scanning calorimetry, heat, hydrolysis, in vitro digestibility, iodine, light microscopes, lipids, parboiling, physicochemical properties, pressure cooking, resistant starch, rice, seeds
Parboiling is widely used world-wide, but properties of the final products depend upon processing conditions and rice variety yielding complex results. This study intended to understand the formation of amylose lipid complex (ALC) after parboiling combined with heat moisture treatment (HMT). Differential scanning calorimetry (DSC) and X-ray diffraction were utilized to understand the properties of the parboiled rice. In vitro starch hydrolysis was employed to evaluate the digestibility of the products. The distributions of protein and starch in rice kernels were observed using a light microscope. Data from amylose content measurement using iodine indicated the formation of ALC after parboiling and HMT. The presence of type II ALC was confirmed by DSC and X-ray diffraction. Pressure cooking increased the resistant starch (RS) from 1.95 to 7.95%. Resistant starch (RS) and slowly digestible starch (SDS) were further increased to 10.4% and 45.8%, respectively, by HMT after parboiling. The data indicated that pressure cooking and HMT could increase the contents of RS and SDS of rice, along with other potential health benefits.