EFFECT OF TWO STAGE DRYING EMPLOYING FLUIDIZED BED DRYING, TEMPERING FOLLOWED BY FIXED BED DRYING ON HEAD RICE YIELD OF BRRI DHAN28 RICE VARIETY IN BANGLADESH

Abstract

Drying of high moisture paddy to achieve quality milled rice is an important issue in a paddy producing country like Bangladesh. This study has been conducted to investigate the impact of two stage drying technique namely, fluidized bed drying, tempering and followed by fixed bed drying method on quality of BRRI Dhan28 rice variety in terms of head rice yield (HRY). Moist paddy was dried in fluidized bed dryer (FBD) as first stage drying to reduce moisture from 25-27% to 18-19% using three drying temperatures of 120, 130, and 150°C at three bed thicknesses of 8, 10, and 12 cm. The first stage dried samples were immediately tempered for 30 minutes and dried in second stage drying by fixed bed dryer using 40±10C temperature maintaining bed thickness as 30 cm for the further reduction of moisture content to 13-14% (wb). Sun drying method was followed as complete drying of control sample. Control sample was used to compare the milling quality of rice dried in two stage drying technique. In addition, head rice yield was also compared to existing industrial paddy drying complexes. The results revealed that HRY of rice samples obtained from different drying methods was comparable. All the sets of drying parameters in two stage drying yielded better quality HRY than the control and even existing industrial drying method. The highest HRY (53.43%) of milled rice was obtained in the two-stage drying. On the other hand, the samples dried in the sun drying and industrial drying using Louisiana State University (LSU) dryer yielded 49.77% and 48.25% HRY, respectively. Therefore, the two-stage drying technique can be used for drying of high moisture paddy to obtain quality dried rice.