Quality Aspects of Paddy Dried in Two Stage Drying Employing Fluidized Bed Drying, Tempering Followed by Fixed Bed and Sun Drying Method

Quality evaluation of paddy dried by two stage drying technique

Abstract

This study aimed to investigate the impact of two options of two stage drying technique: (a) Fluidized bed drying, tempering and followed by sun drying method and (b) 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 drying temperatures of 120, 130, and 150°C at bed thicknesses of 8, 10, and 12 cm. The samples were immediately tempered and dried in second stage drying by fixed bed dryer using 40±1°C temperature maintaining bed thickness as 30 cm for the further reduction of moisture to 13-14% (wb). Sun drying method was followed as second stage drying and for complete drying of control sample also. 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. It is interesting that the HRY obtained in the first option was again better than the control and even existing industrial drying method. The highest HRY (65.57%) of milled rice was obtained in the first option and comparatively lower (53.43%) in the second option of two stage drying. On the other hand, the samples dried in the sun drying and industrial drying using Louisiana State University (LSU) dryer yielded 52.77% and 51.25% HRY, respectively. Therefore, the two stage drying technique can be used for drying of high moisture paddy to obtain quality dried rice.