Hot-air batch dryer for paddy: evaluation of performance and quality of dried paddy

This study aimed to assess the drying performance of an electric-powered hot-air batch dryer. Freshly harvested paddy (BG350) with initial moisture contents of 18.62 ± 1.75% and 21.91 ± 2.54% (wet basis) was dried at bed thicknesses of 0.10 m and 0.25 m, and evaluated for moisture content, germination rate, and head rice yield using two-way ANCOVA and non-linear regression. Performance evaluation was conducted according to ISO 11520-1:1997 standards. According to the results, the moisture content of paddy was lowered to 13.56±0.35% and 14.38±0.08% (wet basis) within 70 and 140 minutes of drying time for 0.10 m and 0.25 m bed thicknesses, respectively. The drying curves illustrated a falling-rate period. The drying rate constant (k) was 0.0059 for the 0.10 m bed and 0.0035 for the 0.25 m, confirming that drying was faster at the lower bed thickness, as indicated by the higher k value. Statistical analysis revealed that, after controlling for initial moisture content, both bed thickness and drying time had a significant effect (p ≤0.05) on the final moisture content. Bed thickness also significantly affected (p ≤0.05) germination rate, cracked grain percentage, and head rice yield. However, discoloration analysis indicated no significant effect of bed thickness or initial moisture content on grain color. In conclusion, the study demonstrated that the paddy bed thickness in the electric-powered hot-air batch dryer significantly impacts both drying efficiency and quality of dried paddy. These findings provide valuable insights for optimizing drying conditions to enhance paddy quality and dryer performance.