Effect of the drying process on the physical properties and cooking quality of japonica aromatic rice [Oryza sativa]
2006
Hashemi, J.(Tsukuba Univ., Ibaraki (Japan)) | Shimizu, N. | Kimura, T.
Rice is a major economic crop in Iran, where it is usually dried using a batch-type dryer until the final moisture content (FMC) reaches below 9%. The influence of low FMC (about 9%) produced by four drying temperatures (30, 40, 50, and 60deg C) on the physical properties, milling, and cooking qualities of short grain aromatic rice were investigated. The obtained data were also compared with standard FMC (about 12%.) treatments which were dried in a batch type dryer. The experimental result showed that for low FMC samples, head rice yield (HRY) was increased by 4% at drying temperatures of 30 deg C and 40 deg C but was reduced by about 20% at 60 deg C in comparison with control sample (25 deg C, 60% RH) . The water uptake ratio (WUR) and volume expansion ratio (VER) were decreased significantly as the drying temperatures were increased. We can conclude that low FMC (9 %) could produce higher HRY, if the drying temperature is 40 deg C or less. In addition, high drying temperatures (50 deg C and 60 deg C) caused increases in the number of fissured kernels, energy consumption and decreases in HRY, WUR, and VER. Maintaining the HRY and keeping a cooking quality at maximum level are the main task for the optimization of drying process. It was occurred at drying temperature less than 40 deg C with a low FMC for aromatic rice. Therefore, a drying temperature of more than 40 deg C would result in deterioration of quality of japonica type aromatic rice, followed by low FMC.
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