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Laboratory-Scale Characterization of a Purple Rice Variety: Examination of Milling Quality and Determination of Anthocyanin and Oil Concentration across the Bran Layer

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Transactions of the ASABE. 55(4): 1577-1582. (doi: 10.13031/2013.42226) @2012
Authors:   R. Schramm, M. Plater II, N. Walker, S. Jang, J. Xu, M. Lima
Keywords:   Anthocyanin, Milling quality, Oil, Purple rice, Rice bran, Value-added processing

Assessment of rice milling quality for new rice varieties and characterization of phytochemicals within the rice bran layer provide important information for optimization of milling and evaluation of the extraction potential for value-added products. In this study, we characterized the milling quality of a purple rice variety (line number MCR02-1576) and measured oil and anthocyanin concentration in the bran layer. After shelling, samples were milled for different lengths of time with a McGill mill and assessed for degree of milling (DOM), whiteness, transparency, milling recovery, and the amount of bran removed at specific milling times. Bran samples were evaluated for anthocyanin and oil concentration. Results showed that this rice variety exhibited low milling recovery (<50%), whiteness (<15%), and transparency (<1%) when compared to non-pigmented rice varieties. The whiteness and transparency values indicate that purple pigment is present in the kernel as well as the bran layer, unlike most other purple rice varieties. DOM was not measurable. Anthocyanin concentration increased linearly with milling length across the entire bran layer. Oil concentration also increased linearly across the inner bran layer. The mean inner bran layer oil concentration was 22%. Processing to obtain the inner fraction of the bran layer for this variety maximizes anthocyanin and oil recovery.

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