Optimization of process variables of multilayer mechanical drying of white button mushroom (Agaricus bisporus)
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
Studies were carried out on optimization of process variable for multilayer mechanical drying of white button mushroom (Agaricus Bisporus). The drying of mushroom was carried out at 3 levels each of temperature (45-650C), air velocities (1.0-5.4 m/s), and loading densities (26-52 kg/m2). Single layer drying with loading density of 10 kg/m2 was kept as control. For optimization of multilayer drying process variables ‘RSM’ 3 - Factor Box–Behnken was used. Samples dried at optimized conditions were packed and stored for 5 months under refrigerated and ambient condition. The drying parameters included moisture content, drying rate, temperature and relative humidity of outgoing air, product temperature, heat utilization factor, coefficient of performance and specific energy consumption. Quality attributes included rehydration ratio, shrinkage ratio, ascorbic acid, texture (hardness), colour, protein and overall acceptability. Mushroom with an initial moisture content of 91.80 ± 0.5 (% wb) was dried in mechanical drier (SATAKE) till it reached final moisture content of 6.35 - 6.10 %db. The decline in drying rate increased with temperatures, air velocities, whereas opposite trend was observed for loading densities. Maximum drying rate (17% db/min) was observed for 650C, 5.4m/s and 26 kg/m2. The average temperature of outgoing air, temperature of product and specific energy consumption was lower than that of single layer drying but opposite trend was observed for relative humidity, heat utilization factor, coefficient of performance. Logarithmic model showed the highest adequacy of fit for both multilayer and single layer drying. The effective moisture diffusivity (Deff) increased with temperature, air velocity and decreased with loading density. The highest Deff of 4.92×10-06 and 5.40×10-06 m2/s was observed for multilayer and single layer drying respectively. It was concluded that Button mushroom dried by multilayer drying at 550C, 5.4 m/sec and 43 kg/m2 will give better quality product compared to single layer drying. Multilayer dried button mushroom packed in laminate can retain quality for 5 and 3 months under refrigerated and ambient condition respectively. Multilayer drying resulted in capacity enhancement by 2.34 times to that of single layer drying, alternatively single layer took 4.30 times more time to that of multilayer drying, to dry the same amount of product.
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