Infrared radiation drying of parboiled rice: Influence of temperature and grain bed depth in quality aspects

The main objective of this study was to optimize the infrared radiation (IR) drying of parboiled rice on the temperatures of 70, 100, and 130°C and grain bed depth of 5, 10, and 15 mm. The effects of the temperature and grain bed depth on drying kinetics, head rice yield (HRY), milling and color parameters, and cooking properties were evaluated using response surface methodology. The drying temperature and bed depth presented a significant effect on HRY, whiteness, transparency, milling degree, L*, C*, relative crystallinity, cooking time, leached amylose, solubilized protein, and hardness. The longer exposure times to IR resulted in grains with an increase in the intensity of endosperm fissures and lower HRY. There is a tendency that the best condition to dry parboiled rice with IR is at higher temperatures and lower grain bed depth. PRACTICAL APPLICATIONS: The present study optimized infrared radiation drying of parboiled rice as a function of the drying temperature and grain bed depth. The results provide scientific support on making decision during industrial rice processes. Severe infrared radiation drying conditions can reduce the HRY, increase cooking time, and intensify undesired sensory attributes.