Effect of Far Infra-Red radiation on paddy parboiling and milling qualities

Abstract

Paddy parboiling is a hydrothermal process applied as a treatment to rough rice, prior to normal milling stage. The parboiling process consists of three separate operations as; soaking, steaming and drying. The traditional parboiling soaking process needs high water consumption, causes high water pollution, air pollution and high energy consumption than using far –infrared (FIR) method. This study was conducted to use the FIR on parboiling process and to test quality of milled rice. The paddy sample BG358 (1kg) was selected and measured its initial moisture content and different soaking moisture contents from the sample were prepared as: 22%, 25%, 28% and 31% respectively for parboiling. Parboiling process was done at 175 0C for 20s by using FIR in 3 different distances as: 20cm, 30cm, 40cm and 3 replicates for each samples and rice cooker (100 0C, 25 min) used as control method. Milling qualities of par boiled rice were tested. The white belly rice percentage and broken rice yield percentage were significantly low in samples soaked up to 28% and the total rice yield and head rice yield were not significantly difference with control samples. The selected qualities were not influenced by various radiation intensities while the white belly rice only showed significantly less yield in 30 cm distance. The energy consumption of FIR was 0.005445kWh while the energy consumption was 0.416 kWh from traditional method. Moisture content of soaked paddy was identified as main cause for broken paddies.