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The effect of induced yellowing on the physicochemical properties of specialty rice

Bryant, Rolfe J., Yeater, Kathleen M., Belefant-Miller, Helen
Journal of the science of food and agriculture 2012 v.93 pp. 271
amylose, cooking quality, gelatinization, industry, laboratory techniques, physicochemical properties, profits and margins, proteins, rice, seeds, sushi, temperature profiles, viscosity
BACKGROUND: Postharvest yellowing (PHY) of rice kernels can be a major problem in the rice industry. This is especially true with high-valued specialty rice, because profit loss will be greater. The objective of this work was to determine whether a significant change occurs in the physicochemical properties (apparent amylose and protein concentrations, viscosity profile and gelatinisation temperature) as a result of induced PHY. RESULTS: In this study, four specialty rices (Basmati, Jasmine, Arborio and Sushi)were yellowed using a laboratorymethod. PHY increased apparent amylose concentration. It also significantly increased onset andpeak gelatinisation temperatures. However, peak, breakdown and setback Rapid ViscoAnalyzer viscosities were decreased by PHY. Trough viscosity forBasmati and Jasmine decreased, whereas it increased for Arborio. Moisture and protein concentrations were unchanged by the yellowing process. Attempts to rehydrate the kernels after induced PHY caused them to fracture, thus making them unsuitable for their intended purpose. CONCLUSION: This study indicates that rice that has been subjected to PHY shows a reduction not only in appearance but also in cooking and processing quality, decreasing its value. However, the changes differed for each rice type, with Jasmine being affected the least.