Biochemically assisted rice whitening for improving head rice yield

Abstract

AbstractThe maximum attainable head rice yield in conventional long grain rice milling is approximately 64%, with around 15% being lost as a result of broken rice kernels. The primary objective of this project was, therefore, to improve the milling yield. To achieve this goal, biochemically assisted whitening processes involving the application of different aqueous solutions were evaluated. Head rice yield was increased for all tested liquids (3.3–3.8% depending on liquid) for Gladio‐type brown rice treated with 0.5% liquid prior to whitening to 40 Kett using a lab‐scale horizontal friction‐type McGill whitener. However, the moistening led to increased caking in the McGill milling chamber. In comparative trials, the use of moistening solutions containing enzymes, sorbit, or sodium chloride instead of pure water delivered a slightly, but nevertheless, significantly higher degree of whiteness directly after milling while it did not result in a significant reduction in the number of broken kernels. Since average head rice yield has a 43% higher commercial value than broken kernels, the 3.6% improvement in milling yield achieved by adding 0.5% water would result in an estimated increase in profit for a 7.5 t/h rice mill of 0.83%.Practical applicationsRice as a global staple food bears a critical role in human nutrition. At the same time, the quality of milled rice is a key buying and price criterion in rice‐consuming countries. One key quality criterion is the number of brokens in rice. Hence, it is critical for rice millers to minimize the degree of broken kernels. Biochemically assisted rice whitening for improving head rice yield is a combined biochemical and physical method to facilitate bran removal from brown rice. The main aim of the present study was to investigate the effect of biochemically assisted rice whitening on the number of brokens and to assess potential technological challenges resulting from the liquid addition.