Textural properties, resistant starch, and in vitro starch digestibility as affected by parboiling of brown glutinous rice in a retort pouch

Abstract

© 2019 The Author(s). The effects that two preparation methods (parboiling with different degrees of gelatinization and parboiling with enzymatic hydrolysis) have on the qualities of brown glutinous rice were investigated in order to optimize the pretreatment conditions of brown glutinous rice for the ready-to-eat product in retort pouch. The brown glutinous rice was parboiled at various temperatures (50, 70 and 900C) and steamed at atmospheric pressure until the gelatinize level of 60, 80 and 100%. For the parboiling with enzymatic hydrolysis, the brown glutinous rice was immersed in xylanase before steamed. Results showed that parboiling not only affected the nutritional composition, color, and texture of glutinous rice but also decreased the Glycemic index (GI) to 61.3 ± 0.03 and raised the Resistance starch (RS) to 2.9 ± 0.02. There was interaction among RS, GI, and the amylopectin content of brown glutinous rice during parboiling without enzymatic hydrolysis. Amylopectin is directly proportional to GI but inversely proportional to RS. Enzymatic hydrolysis improved both the texture and the physical and chemical properties. In addition, the GI value of enzyme treated samples decreased to 62.7 ± 0.24 and the RS increased to 2.9 ± 0.05. The highest overall preference score was attained by parboiled rice which was soaked in water at 90°C and then steamed until 100% gelatinization.