Comparison on drying characteristic, efficiency, unit drying cost and quality of maize dried by a novel multi-crop mobile dryer, existing industrial dryer and sun drying method

Abstract

This research aimed to investigate the effects of different drying methods on drying characteristic, drying efficiency, unit drying cost and quality of maize grain dried by newly developed HSTU multi-crop mobile dryer (HMMD) which was operated by alternative heating sources such as LPG and electric heater (EH), existing HSTU multi-crop industrial dryer (HMID) which was operated by rice husk fired cyclonic furnace and sun drying method. The comparative drying experiments were carried out at the drying temperature of 60±5 °C, 70±5 °C and 80 ± 10 °C for HMMD-LPG, HMMD-EH and HMID, respectively, while sun drying was accomplished at 30±5 °C. The results indicated that the HMMD was capable of drying 820 ± 10 kg maize in each batch from 29.8 ± 0.87 % (wb) moisture to 14 ± 0.56 % (wb). Drying time in HMMD-LPG, HMMD-EH, HMID, and sun drying were 8.24 ± 0.18, 7.36 ± 0.17, 10.18 ± 0.16 and 16.14 ± 0.24 h, respectively, indicated that HMMD reduced time significantly for drying of freshly harvested maize. Unit drying cost in BDT/kg for EH and LPG integrated HMMD was 2.64 ± 0.17 and 1.69 ± 0.10, respectively, while lesser unit cost was found in HMID and sun drying methods. However, drying efficiency of HMMD-LPG was the highest (64.79 ± 1.21 %) while HMID exhibited the lowest drying efficiency (49.42 ± 1.63 %). Mechanically dried grain especially by HMMD-LPG was better or comparable in terms of nutritional quality than sun dried maize. HMMD-LPG and HMMD-EH dried grain exhibited a lower ΔE value than HMID and sun dried samples which indicated that the color properties were not affected so much by the drying method. Furthermore, maize samples dried in HMMD had lower microbial loads than other products. Therefore, the HSTU multi-crop mobile dryer with alternative heating source is recommended as an alternative drying technique for quick and safe management of high moisture maize at farm level in Bangladesh and other subtropical countries in contrast to weather depended sun drying method.