Effect of heat treatment on starch granule structure and nutrient content of germinated purple rice

Abstract This study aims to determine the effect of heat treatments on milling quality and some nutrients of germinated glutinous purple rice; we performed an experiment in a 3x2 factorial design with three replications. The first factors were three heating methods, namely; baking (80, 100 °C) and steaming (100 °C), and the second factors were two heating periods (15 and 30 min). Dried germinated rice was used as control. Heating method and duration as well as their interactions, significantly affected the milling quality and anthocyanin extraction (P &lt; 0.05). Steaming at 100 °C for 30 min significantly increased head rice (73.4%), while baking at 100 °C for 30 min resulted in the highest amount of broken rice (42.3%). These method also maintained the GABA (γ-aminobutyric acid) content of the rice, while anthocyanin extraction was decreased from 52.1 to 29.9 mg•g-1. Heating at 80 °C for 30 min, 100 °C for 10 and 20 min and 125 °C resulted in a higher free radical scavenging ability when compared to unheated rice.摘要 本研究旨在探究热处理对发芽糯紫米碾磨品质及部分营养成分的影响。本实验采用3×2因子设计，设置三次重复。第一因子为3种加热方式，分别为80℃烘烤、100℃烘烤及100℃蒸煮；第二因子为2个加热时长（15 min与30 min）。以未加热的干燥发芽糯紫米作为对照组。加热方式、加热时长及其交互作用对碾磨品质与花色苷提取率均有显著影响（P < 0.05）。其中，100℃蒸煮30 min可显著提升整精米率至73.4%，而100℃烘烤30 min则导致碎米率最高达42.3%。该处理同时可维持稻米中γ-氨基丁酸（GABA，γ-aminobutyric acid）含量，而花色苷提取率从52.1 mg•g⁻¹降至29.9 mg•g⁻¹。与未加热对照组相比，80℃加热30 min、100℃加热10 min、100℃加热20 min以及125℃加热处理均表现出更高的自由基清除能力。