Effects of High Temperature Drying on Rice Quality

Recent research on a form of two-stage drying shows significant advantages in terms of energy saving and quality deterioration, especially fungal deterioration. In two-stage drying, the first stage uses high-temperatures (up to 150°C) to reduce grain moisture from field level to about 18 % wet basis quickly. The first stage is followed by a second stage, usually performed at near-ambient temperature, which will reduce the moisture content to 14 % wet basis, which is adequate for storage or milling of rice. There are obvious advantages in adopting the two-stage drying concept, such as an increase in drying capacity of the first-stage dryer and low energy consumption in the second stage resulting in a substantial overall energy saving. It was found that recent development of a commercial-scale fluidised bed dryer and current work on spouted bed dryers make these dryers suitable options for the a first stage dryer. The quality of both long and medium grain rice were compared over three drying strategies; fluidised bed drying at 80-90°C (single stage), fluidised bed and in-store drying (two stage) and in-store drying alone (single stage). Quality aspects measured were head rice yield, gel consistency, water absorption, volume expansion, amylose content, pasting properties, digestibility and ergosterol levels