MULTI-LAYER DRYING OF GINGER (Zingiber officinale
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Date
2011
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PAU Ludhiana
Abstract
Investigations were carried out to study the effect of drying parameters on multi-layer drying of ginger. The drying parameters studied were moisture content, drying rate, temperature and relative humidity of outgoing air, product temperature and heat utilization factor. Quality attributes included rehydration ratio, coefficient of rehydration, shrinkage ratio, volatile oil content, colour. The multi layer drying was carried out at 60°C in Satake mechanical drier till an average moisture content of 5-6 % was achieved. The total drying time was between 5-16.5 hours. It was observed that moisture content, 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 decrease in moisture content increased with increase in air velocities whereas opposite trend was observed for loading densities. Drying rate was higher for higher air velocity but opposite for loading density. A maximum heat utilization factor was observed for high loading density and low air velocity. Increase in air velocity resulted in decrease in heat utilization factor and relative humidity however temperature of outgoing air and product showed the opposite trend. Similar effect was observed for loading density. At air velocity 3.11 m/s the drying rate was maximum (8.45% db/min) for loading density 27.99 kg/m2 and heat utilization factor was maximum (1.00) for loading density 87.01 kg/m2. The rehydration ratio and coefficient of rehydration were maximum for sample having low loading density and air velocity but shrinkage ratio and volatile oil content were minimum for combinations having high loading density and low air velocity. There was a significant change in colour of fresh and rehydrated samples. The optimum conditions for multi-layer drying of ginger were observed to be 44.66 kg/m2 loading density and 3.5 m/s air velocity and corresponding values of rehydration ratio, coefficient of rehydration, shrinkage ratio, volatile oil and colour change were 4.98, 0.64, 1.87, 1.15 and 5.72 respectively.
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