Application of Two-Stage Variable Temperature Drying in Hot Air-Drying of Paddy Rice

Abstract

The aim of this study was to investigate the effect of two-stage variable temperature drying (VTD) on the quality and drying efficiency of paddy rice in the hot air-drying process. A constant temperature of 50 °C (CTD) was used as a control group. VTD and CTD methods were applied in a 15 ton batch type recirculating grain dryer. Three aspects (appearance quality, physical and chemical properties, taste quality) of the paddy rice samples from the dryer were measured and compared. It was observed that paddy rice with an initial moisture content of 25.3% (wet basis) was dried to 14% (wet basis). Compared to CTD, the VTD method could reduce the drying time and fissuring rate by 0.7 h and 42%, respectively. It had a head rice yield (HRY) of 78.45%, compared to 76.45% by CTD. The fatty acid content of the VTD samples was 2.28% lower than those of CTD, and it exhibited a 34% decrease in amylose content. These results show that two-stage VTD is an advanced hot air-drying method that can be used to improve the quality of dried paddy rice, maintain efficiency, and reduce the cost of the drying process by minimizing the rate of energy consumption.

Effect of variable temperature levels on drying characteristics and quality indices of rice in continuous drying and multi‐stage intermittent drying

“…From Figure 5b, it can be seen that the HRY after drying in the MID was significantly higher than that in the CD at different hot‐air temperature levels (Δ0, Δ5, and Δ10). The diffusion of water inside the rice increased significantly, and the moisture gradient became larger during CD, leading to cracks due to increased internal stress (Xu et al, 2022). The variation of HRY was very small under low‐temperature drying conditions at 35 and 45°C.…”

“…The diffusion of water inside the rice increased significantly, and the moisture gradient became larger during CD, leading to cracks due to increased internal stress (Xu et al, 2022). The variation of HRY was very small under low-temperature drying conditions at 35 and 45 C. This is due to the fact that under low-temperature conditions, the moisture gradient and temperature gradient are relatively small, and the effect is not obvious after increasing tempering treatment.…”

“…Variable temperature drying technology is currently used in many agricultural products, especially rice and maize (Akhtaruzzaman et al, 2021; Sarker et al, 2014). Variable temperature drying is achieved by using different temperatures according to the different drying stages of the material, and the temperature can be changed in various modes (Xu et al, 2022). Chayjan et al (2018) investigated the drying characteristics of rice using gradual changes in drying temperature based on the glass transition theory.…”

Online Detection of Impurities in Corn Deep-Bed Drying Process Utilizing Machine Vision

“…Grain deep-bed drying is a multiple disturbance process under the complex environment of high humidity, high dust, and light change [ 25 , 26 ]. Under this condition, if the acquired image is recognized without pre-processing, an error of impurity recognition may be introduced by noise interference.…”

Analysis of quality changes and hot air drying characteristics of Xinjiang jujube (Zizyphus jujuba cv. Junzao) by hang on trees drying

“…Many scholars have investigated the changes in fruit quality with growth stage [13] . Gou Xi et al2014 [14] investigated the changes in cyclic adenosine phosphate, soluble sugar and mineral element content of Lingwu jujube at different maturity levels.…”