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Subject: Processing and Food Engineering × Author: Sakti Bansal × End date: 2017 × Start date: 2011 × Thesis Type: M.Sc ×
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    OPTIMIZATION OF CONVECTIVE-CUM-MICROWAVE DEHYDRATION OF OYSTER MUSHROOMS (Pleurotus sajor-caju)
    (2013) Sakti Bansal
    Investigations were carried out to study the effect of drying parameters viz. loading density, air velocity, power level on convective-cum-microwave dehydration of oyster mushroom. Multi layer drying of commercially grown mushroom cv. Pleurotus sajor-caju was carried out at 3 levels of loading densities (26-52 kg/m2) and air velocities, 3-5 m/s and microwave drying was carried out at 3 power levels (270-810 W). The drying parameters studied were drying rate, temperature and relative humidity of outgoing air, product temperature and heat utilization factor. Quality attributes included rehydration ratio, shrinkage ratio, texture (hardness and chewiness), colour and overall acceptability. Multi layer drying of mushroom with an initial moisture content of 91% wb was carried out at 60°C in a mechanical drier till the moisture content reached 27% wb followed by drying in microwave oven to a final moisture content of 6.89% wb. It was observed that drying rate, relative humidity of outgoing air and heat utilization factor decreased with drying time but opposite trend was observed for temperature of outgoing air and product. The decline in drying rate increased with increase in air velocities and power level whereas opposite trend was observed for loading densities. Increase in loading density and air velocity resulted in decrease in heat utilization factor and relative humidity however temperature of outgoing air and product showed the opposite trend. Logarithmic model showed the highest adequacy of fit for multi layer drying and two term exponential model for microwave drying. The effective moisture diffusivity increased with increase in both loading density and air velocity. The increase in loading density resulted in increase in rehydration ratio, shrinkage ratio, colour change but decrease in texture and overall acceptability. The increase in air velocity resulted in increase in rehydration ratio, hardness, colour change overall acceptability but decrease in shrinkage ratio and chewiness. The increase in power level resulted in increase in rehydration ratio, texture, colour change and decrease in shrinkage ratio and overall acceptability. The optimum conditions for convective-cum-microwave drying of mushroom were found to be 38.80 kg/m2 loading density, 3.86 m/s air velocity and 413.6 W power level. Keywords: Oyster mushroom, drying kinetics, quality, optimization