Effect of rice variety and milling fraction on the starch gelatinization and rheological properties of rice milk

Abstract This study aimed to investigate the rheological properties of rice milk produced from raw rice including rice varieties and milling fractions. Rice milk was prepared from two rice varieties, which were Arhent (long grain) and Bengal (medium grain) using brown, head and broken fractions of the two cultivars used. Gelatinization temperatures for each rice variety, milling fraction, and rheological behaviors of rice milk were examined. Flow behaviors of rice milk were significantly affected by the variety and milling fractions of raw rice. The different amylose to amylopectin ratios of the two varieties, the compositional differences and the subsequent impact on the gelatinization temperature of raw rice used in rice milk were the primary reasons for these differences. Rice milk prepared from Bengal showed greater consistency coefficients, showing a Newtonian flow behavior compared to the rice milk made from Arhent variety. Broken rice showed a potential to be as a raw material in the rice milk industry since it showed similar flow properties compared to the head rice (i.e. within the same variety).

摘要 本研究旨在探究以原稻米（涵盖稻米品种与碾磨分级）制备的米浆的流变学特性（rheological properties）。本研究选取长粒型品种Arhent与中粒型品种Bengal的糙米、整米及碎米分级作为原料，制备米浆样品。分别测定了各稻米品种、碾磨分级对应的糊化温度（gelatinization temperatures），以及米浆的流变行为。米浆的流动行为受原稻米品种与碾磨分级的影响极为显著。两个品种直链淀粉（amylose）与支链淀粉（amylopectin）比例的差异、组分差异，以及由此对米浆制备所用原稻米糊化温度产生的影响，是造成上述流变行为差异的核心原因。由Bengal制备的米浆表现出更高的稠度系数（consistency coefficients），相较于Arhent品种制备的米浆，其流动行为更符合牛顿流动行为（Newtonian flow behavior）。同品种下，碎米与整米的流动特性相近，因此碎米具备作为米浆工业生产原料的应用潜力。