Dynamics of Texture Change and in Vitro Starch Digestibility with High-Pressure, Freeze-Thaw Cycle, and Germination-Parboiling Treatments of Brown Rice

Abstract

HighlightsFreeze-thaw cycle (FTC) treated brown rice texture was much closer to white rice texture.Both high-pressure (HP) and FTC treatment helped to moderate the bran layer of brown rice.FTC treatment of brown rice resulted in higher conversion to resistant starch.The glycemic index of treated rice correlated positively with the amylose/amylopectin ratio.Abstract. High-pressure (HP), freeze-thaw cycle (FTC), and germination-parboiling (GP) treatments were used to improve the texture characteristics and in vitro digestibility of starch in brown rice (BR). The texture of FTC-treated BR was the closest to the texture of white rice. Improved water absorption ratio, HP and FTC induced modification of the bran layer, and GP induced partial starch gelatinization were considered to be responsible for improving the texture of BR. All treatments improved the in vitro digestibility of BR starch, and FTC < HP < GP with respect to the order of increase. FTC treatment also resulted in the minimal glycemic index (GI), while GP treatment resulted in higher GI. In general, the amylose content was lower for untreated BR than for treated BR. Further, the HP, GP, and FTC treatments showed improved amylose/amylopectin ratios. HP and GP decreased the gelatinization enthalpy, while FTC increased it. GI had a positive correlation with amylose content and amylose/amylopectin ratio, while gelatinization enthalpy had a negative correlation. Keywords: Brown rice, Freeze-thaw cycle, Germination-parboiling, High pressure, Starch in vitro digestibility, Texture.