EFFECTS OF DRYING AND TEMPERING RICE USING A SINGLE PASS DRYING PROCEDURE

Abstract

The objective of this research was to determine the effects of various drying and tempering strategies on rice quality using a continuous drying procedure. The drying procedure used was designed to implement a hypothesis involving the glass transition temperature of rice as applied to moisture content removal rates and tempering durations. The drying procedure consisted of four stages. First, rice was dried in a chamber for various durations aimed at removing 1 to 6 percentage points of moisture content. The rice was then sealed in plastic bags and tempered inside the drying chamber for certain durations, as determined in previous research, to reduce moisture content gradients within the kernels. The rice was then dried further to approximately 12 to 13% moisture content. After this second drying stage, the rice was again tempered. There was little to no reduction in head rice yield when less than 4 to 5 percentage points of moisture content were removed during the first drying stage. Conversely, if drying exceeded 4 to 5 percentage points removal, there was a significant reduction in head rice yield; additionally, tempering did not prevent head rice yield reduction under these drying scenarios. Also, if less than 4 to 5 percentage points were removed during the first drying stage, then drying could continue after sufficient tempering without head rice yield reduction.