Infrared-Convective Drying of Turmeric Slices

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Date
2011
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Publisher
MPUAT, Udaipur
Abstract
Turmeric (Curcuma longa) is an important foreign exchange earning crop commercially grown in India. India is believed to be the home of turmeric. India has the largest share in production, consumption and export of turmeric in the world. It accounts for 78 per cent of the world output and 60 per cent of world exports. Indian turmeric is considered the best in the world market because of its high curcumin content. Growth in popularity of convenient foods in many countries has stimulated increasing demand for high quality dehydrated turmeric powder which has more curcumin content. Use of infrared radiation for drying of agricultural produce is a novel technology in drying of foods. An infrared-convective technology for drying of turmeric slices was adopted to study drying kinetics. For the experiment, locally available turmeric rhizomes were used. The effects of process variables such as infrared power (300, 400 and 500 W), drying air temperature (30, 35 and 400C) and drying air velocity (1.0, 1.5 and 2.0 m/s) on drying time, moisture diffusivity, water activity, heat and mass transfer coefficients, colour and curcumin content, specific energy consumption were studied. The infrared-convective drying process, for infrared power of 300 W and air temperature 300C with air velocity 1.0, 1.5 and 2.0 m/s, it took about 3.9, 4.2 and 4.5 h, respectively for drying of 100 g of turmeric slices. Similarly for infrared power 500 W and air temperature 400C with air velocity 1.0, 1.5 and 2.0 m/s, it took about 1.3, 1.4 and 1.5 h, respectively. The average moisture diffusivity varied from 3.61 × 10-10 to 10.95 × 10-10 m2/s and was also influenced significantly by infrared power, air temperature and air velocity. The heat transfer coefficient hc ranged between 23.55 and 34.79 W/m2 0C and mass transfer coefficients kc varied from 2.41 × 10-2 to 3.52 × 10-2 m/s during the drying process and Biot mass number was also greater than 100. It was observed that colour (yellowness) value for infrared-convective dried turmeric slices increased from 300 W to 400 W and then decreased slightly from 400 W to 500 W. However, b value range was higher for 400 W (48.66 to 54.16) than 300 W (39.66 to 44.90) and 500 W (36.99 to 54.04). Curcumin content varied from 94.07 to 400.51 mg/100 g solid matter under different infrared-convective drying conditions. The water activity of dried turmeric powder ranged between 0.25 and 0.39 which indicated that product was stable in nature. Specific energy consumption varied from 58.48 to 146 MJ/kg during infrared-convective drying. The process parameters for infrared-convective drying were optimized for the turmeric slices, using Tukey's Multiple pair-wise test. The results revealed that the infrared power of 400 W, air temperature of 350C and air velocity of 1.0 m/s gave a good quality dehydrated turmeric slices and involved low specific energy consumption in the drying process.
Description
Infrared-Convective Drying of Turmeric Slices
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Citation
Acharyya and Sharma, 2011
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