Effect of high temperature intermittent drying and tempering on rough rice quality

Abstract In this work the effect of the number of drying cycles associated with different tempering treatments on rough rice kernel fissuring and head rice yield (HRY) has been studied for initial and final moisture contents usually found in the rice processing industry. For a moisture content reduction of six points percentage drying was performed at 60 °C and in one, two and three steps and these drying experiments were combined with a tempering period at ambient, intermediate and high temperature. Results showed that post-drying tempering at high temperature (60 °C) resulted in greater moisture removals and that drying time reductions up to 38% can be achieved. Percentage of fissured kernels was drastically reduced when drying was performed in two or three steps compared to drying in one step. Tempering at high temperature reduced the percentage of fissured kernels and enhanced HRY independently of the number of drying steps.