Physical and Cooking Properties of Aromatic Rice during Drying Process by Batch Type Dryer

Abstract

Rice is one of the major economic crops in Iran which is usually dried by batch type (BT) dryer until the final moisture content (FMC) reaches to about 8%. The physical properties and cooking quality of short grain aromatic rice dried by BT dryer at different drying temperature and low FMC were investigated. The experiments were carried out at 30, 40, 50, and 60oC drying temperatures with different drying time to reach the standard (about 12%) and low (about 9%) FMC. The sample was dried in control conditions used as a reference. The results showed that drying at low temperature for low FMC could be able to keeping the head rice yield (HRY). The HRY for low FMC was increased about 4% at 30 and 40oC and then reduced about 20% at high drying temperature, in compare of control sample. The drying temperature more than 50oC should be avoided as it gives maximum fissured kernels, lowest percentage of HRY, and maximum energy consumption per unit removal of moisture regardless of FMC. The water uptake ratio and volume expansion ratio was significantly (p<0.05) decreased with the increase of drying air temperature from low temperature up to 50oC and then increased at high drying air temperature. Higher drying temperature attributed to the separation of particular size of starch from the kernels as a residual loss. Eventually, the drying temperature had a major influence on the physical properties, milling, and cooking quality of Japonica type aromatic rice followed by different FMC.