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20191
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Subject: Processing and Food Engineering × Author: Ramandeep Kaur × Start date: 2012 × Type: Thesis ×
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    ThesisItemOpen Access
    Optimization Of Microwave Assisted Multilayer Drying Of Bittergourd For Capacity Enhancement And Energy Conservation
    (Punjab Agricultural University, Ludhiana, 2019) Ramandeep Kaur; Satish Kumar
    Studies were carried out on optimization of microwave assisted multilayer drying of bittergourd (Momordica charantia). The drying of bittergourd was carried out by three different methods: Multilayer drying at 5 levels of loading densities (31-60 kg/m2) and air velocities, 2.6-5.41 m/s; Multilayer-cum-microwave drying at 3 power levels (300-600 W) and exposure time (8-24s) with pause time 30s; Multilayer-cum-customized microwave drying at 3 power level (300-600W), exposure time (8-24s) and air velocity (3-9 m/s) with pause time 20s. The drying parameters included moisture content, drying rate, temperature and relative humidity of outgoing air, product temperature, heat utilization factor and specific energy consumption. Quality attributes included rehydration ratio, shrinkage ratio, ascorbic acid, texture (hardness), colour, protein and overall acceptability. Multilayer drying of bittergourd with an initial moisture content of 91% wb was carried out at 60°C in mechanical drier (SATAKE) till it reached 7.05% db. Optimized result of multilayer drying was used for multilayer-cum-microwave drying; product was partially dried at optimized condition up-to 27% wb followed by microwave drying to 7.05% db. The drying time to reach equilibrium moisture content were found to be between 210 – 480, 190 – 213 and 185 -188 min for multilayer, multilayer-cum-microwave and multilayer-cum-customized microwave drying, respectively. The decline in drying rate increased with increase in air velocities, power level and exposure time whereas opposite trend was observed for loading densities. Maximum drying rate (15.25% db/min) was observed for multilayer-cum-customized microwave. 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. Page model showed the highest adequacy of fit for multilayer drying; Logarithmic model for multilayer-cum-microwave drying and Midli et al model for multilayer-cum-customized microwave drying. The effective moisture diffusivity (Deff) increased with increase in air velocity, power level, exposure time and decreased with increase in loading density. The highest Deff of 1.33×10-05m2/s was observed for multilayer-cum-customized microwave drying, which was 70% higher than multilayer drying. The optimum operating conditions for multilayer drying, multilayer-cum-microwave drying and customized microwave drying were 55.0 kg/m2& 5.0 m/s, 450W & 24s and 450W, 24s & 3.75 m/s, respectively. It was concluded that multilayer drying and multilayer-cum-customized drying resulted in capacity enhancement by 3.3 & 4.84 time more in compare to single layer drying. Alternatively it will resulted in saving drying time by 70 & 79.3% in respective methods. Overall multilayer-cum-customized microwave drying was found to be best method.