EFFECT OF RICE KERNEL THICKNESS ON DEGREE OF MILLING AND ASSOCIATED OPTICAL MEASUREMENTS

Three cultivars of long-grain rice were milled to three degree of mill ing (DOM) levels. Inverse linear relationships were established betwee n surface fat concentration (SFC) and Satake milling meter (MM1B) opti cal DOM measurement values, including whiteness, transparency, and DOM , for the unfractionated head rice within each cultivar. Milled bulk r ice for each cultivar was subsequently separated into thickness fracti ons. Effects of milled rice kernel thickness on SFC and optical DOM me asurements were investigated. For a given DOM level, SFC decreased wit h increasing milled rice kernel thickness up to a thickness of 1.67 mm , after which it remained constant. As the overall DOM level increased , the difference in DOM between thin kernels and thick kernels lessene d, implying that thin kernels were milled at a greater bran removal ra te than thick kernels. Milled rice kernel thickness significantly (at the 0.05 significance level) affected MM1B whiteness and MM1B transpar ency in two of the cultivars because of the predominant effects of the thinner kernel fractions. Within each cultivar, MM1B DOM was not sign ificantly influenced by milled rice kernel thickness.