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. 2022 Feb 11;11(4):519.
doi: 10.3390/foods11040519.

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

Karn Chitsuthipakorn  1 , Sa-Nguansak Thanapornpoonpong  2
Affiliations

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

Karn Chitsuthipakorn et al. Foods. .

Abstract

The objectives of the study on a continuous flow hot air dryer combined with radio frequency heating at different temperatures (HA/RF) (38 °C, 42 °C, 46 °C, and 50 °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.

Keywords: cooking quality; hot air drying; milling quality; paddy; radio frequency heating; rice.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The industrial-scale continuous-flow hot-air dryer with RF heating machine: (a) prototype machine (b) schematic diagram.
Figure 2
Figure 2
Drying rate versus drying time for paddy dried with hot air and hot air combined with various RF heating temperatures.
Figure 3
Figure 3
Drying kinetics for paddy dried with hot air and hot air combined with various RF heating temperatures.
Figure 4
Figure 4
Morphology of different fissure degrees in white rice: (a) white rice with 0 fissure; (b) white rice with 1 fissure; (c) white rice with 2 fissures; (d) white rice with 3 fissures; (e) white rice with 4 fissures; (f) white rice with ≥5 fissures.
Figure 4
Figure 4
Morphology of different fissure degrees in white rice: (a) white rice with 0 fissure; (b) white rice with 1 fissure; (c) white rice with 2 fissures; (d) white rice with 3 fissures; (e) white rice with 4 fissures; (f) white rice with ≥5 fissures.
Figure 5
Figure 5
Triangle test to evaluate the ability of panelists to distinguish cooked rice dried with hot air (A) from cooked rice dried with hot air combined with the different RF heating temperatures (B). The statistical difference was determined using ISO 4120:2004 standardized tables.
See this image and copyright information in PMC

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