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Effect of Temperature, Exposure Duration, and Moisture Content on Color and Viscosity of Rice¹

¹Published with the approval of the Director of the Agriculture Experiment Station, University of Arkansas. ²Graduate assistant and professor of Food Science, respectively, 272 Young Ave., University of Arkansas, Fayetteville, AR 72704. ³Corresponding author. E-mail: tsiebenm@comp.uark.edu Phone: 501-575-2841. Fax: 501-575-6936. ⁴Associate professor, Agricultural Statistics Laboratory, University of Arkansas, Fayetteville, AR 72701.

Rice yellowing is a problem for the rice industry. The objective of this research was to determine the effect of various temperatures and exposure durations at certain moisture content levels on yellowing in rice. Preliminary experiments were performed on stored Oryza sativa L. ‘Cypress’ rice. These experiments showed that exposure temperature and duration had a great effect on yellowing, but that the effect of moisture content was not significant (P > 0.15). With this information, similar experiments were performed on freshly harvested ‘Cypress’ and ‘Bengal’ rice. Color degradation, as measured by hue angle and chroma, was observed when at temperatures >50°C for exposure durations >12 hr. Temperatures >55°C with exposure durations >12 hr also resulted in dramatically lowered peak viscosity, but not all samples that showed yellowing had lowered viscosity. For the conditions of these experiments, temperature and exposure duration were the most important factors in color and viscosity change.