Influence of Drying Temperature and Storage Duration on Fissuring and Milling Quality of Jasmine 85 Rice Variety

Abstract

Moisture and temperature gradients induce the development of fissures during drying of paddy kernels. This affects the milling quality of the paddy and eventually reduces the head rice yield. To this effect, a study was conducted to investigate the influence of drying temperature and storage duration on the cracking behaviour and head rice yield of a local rice variety - Jasmine 85. Freshly harvested paddy samples were thin layer dried in a tunnel dryer with varying drying temperatures (45°C, 50°C, 55°C) as treatments and direct sun drying as control. The drying experiment was performed under three replications using a completely randomised design. Samples after drying were stored for three months in sealed plastic bags at room temperature (28°C). Percentage fissures and head rice yield at each drying treatment was determined using a grain scope and a Satake grading machine respectively after the storage period. The highest head rice yield (76.3%) and the least fissure rate (10%) were attained at the control temperature. This was followed by the 45°C and 50°C treatments which gave head rice yields of 70.8%, and 69.8%, with fissure rates of 13% and 16% respectively. The least head rice yield (64.7%) and the highest fissure rate of 29% were observed at 55°C. There was a significant difference (p ≤ 0.05) between head rice yields obtained at 55°C and the control experiment. However, there was no significant difference (p ≤ 0.05) between head rice yield obtained at 45°C, 50°C and the control temperature. It is evident from this study that, Jasmine 85 can be dried by using a mechanical dryer at higher temperatures of 45°C and 50°C without affecting its milling qualities.