STUDIES ON DRYING BEHAVIOUR AND QUALITY OF GARLIC (Allium sativum L.) USING HYBRID DRYING TECHNIQUES

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Date
2013
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PAU Ludhiana
Abstract
Investigations were carried out to study the drying kinetics of garlic slices i.e 3mm size for selected hybrid drying techniques, convective-cum-microwave (CCM) and fluidized-cum-microwave (FCM). The experiments were conducted using completely randomized design (CRD) by varying drying parameters viz. KMS concentration (0.1-0.5 %), drying air temperature (55-75°C) and microwave power level (810-1350 W). The garlic slices were dried to 63(±1) % d.b moisture content by convective tray drying/fluidized bed drying and further dried up to 6(+1) % d.b by microwave drying. Five empirical models were fitted to the kinetics data of convective, fluidized and microwave drying and their adequacy of fit was investigated. Response surface methodology (RSM) was employed for optimization of drying process parameters for CCM and FCM drying using 3-factor Box-Wilson design. Optimization was done on the basis of minimum drying time, specific energy consumption, shrinkage ratio, texture (hardness), non enzymatic browning, maximum rehydration ratio, colour (L-value) and overall acceptability. Dried garlic flakes developed under optimized drying process conditions for both the hybrid drying techniques were packed in three packaging material (Aluminum, LDPE and HDPE bags) and stored under ambient condition (220C to 320C temperature, 45 to 55 % RH). In order to develop garlic flakes, the total drying time varied from 115 to 187.17 and 48 to 72.17 min for CCM and FCM drying respectively. The average effective diffusivity increased with increase in drying air temperature and power level. Among various models checked for their adequacy of fit to the experimental data of drying, the Two term exponential model for convective tray drying, logarithmic model for both fluidized bed and microwave drying were found to be the best fitted model representing the drying kinetics. The optimized drying process parameters obtained were: 0.5 % KMS concentration, 59.41ºC temperature and 810 W power level; 0.1 % KMS concentration, 63.92ºC temperature and 810 W power level for CCM and FCM drying respectively. The dried garlic flakes packed in Aluminum packs was adjudged to be the during three months storage period
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