Cooked Rice Drying by Microwave Assisted Hot Air

doi: 10.14456/mijet.2020.2

Abstract

This research aimed to study the process of instant rice, cooked rice was dried under different microwave power levels. Quality of products was investigated. Milled rice was pretreated by exposing to microwave at power of 800 W for 30 sec and without exposure before cooking with rice cooker.  Cooked rice was dried at drying temperature of 60 °C combined with microwave power at different levels of 0, 400, 600 and 900 W at constant air velocity of 0.23 m/s. Each run used for 500 g. Sample with initial moisture content of 68-72% wet basis was dried down to about 8-11% (aw less than 0.5). Result found that the drying time was affected by pretreatment method and microwave power. The drying time of cooked rice with pretreatment was 386, 170, 140, and 116 min at microwave power of 0, 400, 600 and 900 W, respectively, which was shorter than without pretreatment. Hardness and stickiness of rice with pretreatment were higher than rice without pretreatment. The L*(lightness) and b*(yellow value) of dried cooked rice with and without pretreatment had similar trend that it was decreased when the microwave power increased. However, rehydration ratio of cooked rice with pretreatment was higher than without pretreatment.