Evaluation of drying characteristics, energy consumption and quality of parboiled paddy: Two stage drying

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This study aims to investigate the drying kinetics, energy analysis and milling performance of two common rice varieties namely BRRI-28 and BR-16 by two stage drying. Parboiled paddy samples were dried employing two schemes of two stage drying. First scheme is first stage by fluidized bed drying at temperature profile of (150–170 °C) with fixed bed thickness of 10 cm, tempering (30 min) and followed by fluidized bed drying again using lower temperature 80±2 °C and second scheme is first stage fluidized bed drying (150–170 °C) and tempering and followed by sun drying method. In addition, sun drying method as complete single stage drying was considered as control drying. Drying results indicated that total drying time required in first scheme, second scheme and control drying are 1.4, 4.75 and 11–12 h, respectively. Energy analysis showed that for both paddy varieties, first scheme yielded the highest specific electrical (12.6 MJ/kg H 2 O evaporated) and thermal energy consumption (10.5–11.6 MJ/kg H 2 O evaporated) compare to second scheme (0.58–1.6 MJ/kg H 2 O evaporated) of drying. Milling quality as head rice yield (HRY) was significantly varied among the drying schemes. For BR-16 variety, first scheme yielded the highest HRY (66 ± 0.706%) compare to BRRI-28 variety that yielded the lowest HRY (43.9 ± 0.571%). Better milling recovery (75 ± 0.64%) was obtained in first scheme compare with control dried sample (71 ± 0.56%). Therefore, parboiled paddy is suggested to be dried by any scheme of two stage drying for achieving quality dried grain with minimum energy consumption. • Two schemes of two stage drying was investigated for parboiled paddy. • Energy consumption for drying of parboiled paddy was evaluated. • Total energy consumption varied from 2.06 to 24.6 MJ/kg moisture evaporation. • Head rice yield for two stage dried parboiled paddy varied from 37.5 to 75.66%.