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Lab Scale Characterization of a Purple Rice Variety: Examination of Milling Quality and Determination of Anthocyanin and Oil Concentrations across the Bran Layer

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

Citation:  2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010  1009900.(doi:10.13031/2013.29875)
Authors:   Rebecca C Schramm, Michael Plater, II, Nicole Walker, Sungjoon Jang, Zhimin Xu, Marybeth Lima
Keywords:   Purple rice, milling quality, laboratory scale, anthocyanin, oil

Assessment of rice milling quality and characterization of phytochemicals within the bran layer provide information for optimization of milling conditions and evaluation of the extraction potential for value-added products. In this study, we characterized 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 concentration using HPLC and for oil concentration by weight. 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 percent. Processing to obtain the inner fraction of the bran layer for this variety maximizes anthocyanin and oil recovery.

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