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Usage of spouted bed and microwave assisted spouted bed dryers in bulgur production

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2009
Kahyaoğlu, Leyla Nesrin
The main objective of this study was to investigate the effect of spouted bed and microwave assisted spouted bed drying on drying rates and quality parameters of bulgur. The drying experiments were performed at three air temperatures (50, 70, 90oC) and at two microwave powers (288 W, 624 W). Quality parameters were selected as bulk density, apparent density, apparent porosity, internal porosity, microstructure analysis, and color for dried cooked wheat; yield and water absorption capacity for bulgur. The drying rate increased with air temperature and microwave power. Microwave assisted spouted bed drying at microwave power of 288W and 624 W reduced drying time by at least 60% and 85%, respectively compared to spouted bed drying. The effective moisture diffusivities of bulgur in the spouted bed and microwave assisted spouted bed drying were found to be 2.356x10-10 and 8.398x10-10 m2/s on the average, respectively. The effect of air temperature on product quality except color was not significant in spouted bed drying. Interior kernel porosity, sphericity and L* value of dried cooked wheat increased with air temperature and microwave power. Yield and water absorption capacity of bulgur tended to decrease as microwave power increased. According to SEM analysis, more porous structure was observed in wheat samples dried in microwave assisted spouted bed compared to air dried ones. In microwave assisted spouted bed drying, lower water absorption capacity, bulk density and apparent density, higher sphericity and lighter color were observed as compared to spouted bed drying.