Agricultural Research Service, United States Department of Agriculture (USDA), Western Regional Research Center, Albany, California 94710, United States.
J Agric Food Chem. 2012 Jul 18;60(28):6960-5. doi: 10.1021/jf301263s. Epub 2012 Jul 2.
During rice milling, the bran and germ are successively removed from the caryopsis (kernel). Because bran and germ contain large quantities of lipid, the amount of lipid remaining on the kernel surface may be used as a method for the assessment of milling quality. Bulk samples of rice pureline varieties and an experimental hybrid were milled for 0, 10, 20, 30, and 40 s. Scanning electron microscopy (SEM) revealed that brown rice kernels had large contours of linear protuberances and depressions running lengthwise along the kernel surface. The protuberances were abraded successively during milling, but varying amounts of material remained in the depressions. Light microscopy combined with the lipid-specific probes Nile Blue A or Sudan Black B demonstrated that the material in the depressions observed with SEM was lipid. Sections of whole, milled rice kernels, prepared using a modified sectioning technique and stained with Nile Blue A, showed that portions of the embryo remain after milling and that lipid is located on or near the surface of the kernel. Differences in quantity and distribution of residual lipid as milling duration increased were documented photographically to indicate the extent to which the bran and embryo components were removed during milling. This paper provides proof of concept that residual lipid is a robust measure of the degree of milling.
在碾米过程中，糠层和胚芽会从颖果（米粒）中被逐步去除。由于糠层和胚芽含有大量的脂质，因此残留在米粒表面的脂质含量可以作为评估碾米质量的一种方法。对水稻纯系品种和实验杂交种的大量样品进行了 0、10、20、30 和 40 秒的碾磨。扫描电子显微镜（SEM）显示，糙米的颖果表面具有沿长度方向延伸的线性凸起和凹陷的大轮廓。在碾磨过程中，凸起会被逐渐磨损，但凹陷中会残留一定量的物质。光镜结合脂质特异性探针尼罗蓝 A 或苏丹黑 B 显示，SEM 观察到的凹陷中的物质是脂质。使用改良切片技术制备的全粒、碾磨米粒的切片，并使用尼罗蓝 A 染色，显示出胚乳的部分在碾磨后仍然存在，并且脂质位于或靠近米粒表面。随着碾磨时间的增加，记录了残留脂质的数量和分布差异的照片，以表明在碾磨过程中糠层和胚乳成分被去除的程度。本文提供了一个概念验证，证明残留脂质是衡量碾米程度的一个可靠指标。
