Effect of Large-Scale Paddy Rice Drying Process Using Hot Air Combined with Radio Frequency Heating on Milling and Cooking Qualities of Milled Rice

The objectives of the study on a continuous flow hot air dryer combined with radio frequency heating at different temperatures (HA/RF) (38 degrees C, 42 degrees C, 46 degrees C, and 50 degrees C) in a large-scale process compared with conventional continuous flow hot air drying (HA) were (1) to investigate the drying characteristics, drying kinetics, and milling quality of the process and (2) to observe the cooking quality and compare the sensory differences of the cooked rice after treatment. The drying characteristics and moisture diffusivity showed that the higher the radio frequency (RF) heating temperature, the shorter the drying time. The specific energy consumption and energy cost decreased when the RF heating temperature increased. The optimal condition in terms of fissure percentage was HA/RF42. In addition, there were no significant differences in head rice yield and white rice color determination, amylose content, texture profiles, and pasting properties in all HA/RF treatments. In the triangle test, it was found that at least 6% of the population could perceive a difference between HA and HA/RF50. In conclusion, this study proposes the further development of the HA/RF drying process at low-temperature profiles and shows the great potential of RF technology for commercial drying in rice industry.

Automated summary

The objectives of this study were to investigate the drying characteristics, drying kinetics, and milling quality of a continuous flow hot air dryer combined with radio frequency heating at different temperatures, and to compare the sensory differences of cooked rice after treatment. The results showed that the higher the radio frequency heating temperature, the shorter the drying time. There were no significant differences in various quality attributes of the rice samples treated with different methods. The study suggests the potential of RF technology for commercial drying in the rice industry.