Title: Using residual lipid to assess rice degree of milling Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 30, 2010
Publication Date: July 1, 2010
Citation: Wood, D.F., Siebenmorgen, T.J., Williams, T.G., Orts, W.J., Glenn, G.M., Graves, A. 2010. Using residual lipid to assess rice degree of milling. Meeting Abstract 33:55. Technical Abstract: Color is often used to measure the degree of milling of rice. Milled rice color is determined by the adhering, pigmented bran. Bran and germ are successively removed during milling and those tissues contain large quantities of lipid, therefore, surface lipid content may be used to assess milling quality. Once the bran is removed, small amounts of germ may remain because the germ, a convex structure extending into the starchy endosperm, is not easily removed. Thus, an understanding of grain anatomy is essential to assess milling quality. Fluorescence microscopy combined with a lipid-specific probe provided a procedure to highlight milling characteristics and varietal differences. Standard embedding and sectioning techniques are limited for localization of lipids, because lipids are extracted during the process. Therefore, a protocol for sectioning whole milled rice while preserving lipid was used for this study. Additionally, due to the relatively large surface area of sections, the lipid oxidizes over time, so the sections must be made, stained and documented in a short period of time. Intact rice kernels were encased in paraffin and sectioned with the assistance of clear packing tape. The sections were stained with aqueous Nile Blue A and the resulting characteristic fluorescence of polar lipids was observed in a stereo microscope. Bulk samples of rice pureline varieties and hybrids were milled for 0, 10, 20, 30 and 40 sec. Individual kernels were examined to reveal lipid distribution in the whole-kernel sections. The fluorescence in sections as milling duration increased show how the bran and embryo components were removed during milling. Differences in lipid distribution and remaining lipid in rice varieties and purelines were noted and correlated with data obtained by petroleum ether extraction.