Determination of the optimum intermittent drying conditions for rough rice (Oryza sativa, L.)

Intermittent drying was studied by tempering rough rice (Philippine Seed Board, PSB-RC 52 variety) in between during hot air drying. The study was performed using a three-level, three-factor fractional factorial design and aimed to determine the optimum combination of drying air temperature (X1), air speed (X2) and tempering time (X3) that resulted in high milling recovery (MR), high head rice ratio (HRR), short drying time (DT), high grain hardness (H), high germination ratio (GR), high degree of whiteness (W) and low cracked grains ratio (CGR). Drying air temperatures used varied from 35°C to 55°C. Airspeed, on the other hand, significantly affected H only and tempering time affected DT at the 95% significance level. Optimum drying conditions of 45°C drying air temperature and a tempering time of 2 h were established for the intermittent drying of rough rice.