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UAS develops mechanical cardamom dryer
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Thursday, 16 December, 2010, 08 : 00 AM [IST]
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MV Chandrashekar, Bangalore
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Department of Post Harvest Technology, University of Agricultural Sciences (UAS), Bangalore, has designed and developed a mechanical cardamom dryer. This model consists of drying a chamber, a blower with motor and an electric heating bank. The project was undertaken through a scheme supported by the Indian Council of Agricultural Research (ICAR). The cost of the machine is around Rs 25,000.
In Karnataka, small and medium cardamom growers find it difficult to have a curing arrangement of their own due to financial and other constraints. They normally resort to sun drying which results in low price for their product. Normally the harvested cardamom capsules are spread on mats and dried under the open sunlight for about 3 - 4 days until storable moisture is attained by sun drying. However, the colour obtained is not uniform. Therefore cardamom is bleached to have a uniform look to enhance the market price.
Karnataka is one of the leading states in the production of bleached cardamom. After harvest, the cardamom capsules should be dried immediately to contain the original cardamom capsule colour, otherwise, the colour gradually tends to change from green to golden yellow upon ripening. This is especially significant in case of Malabar variety grown in Karnataka. It retains the golden hue even after drying. However, because of limited production, it has not made any significant impact in the market, while the bold green cardamom are the much sought after ones at premium prices in the Middle East countries.
The traditional practice adopted by the small growers involves sun drying while the large planters have been adopting traditional drying practice in heated rooms. Cardamom curing has to be done within a period of 24-36 hours at a temperature ranging from 55 to 70° celsius. Initially, cardamom capsules are dried at high temperature which is reduced later on. Drying rooms are normally heated by flue gas fuelled by forest waste or by oil, and currently development of drying sheds heated by electricity is also observed. The burning ovens are spread on perforated trays in racks. The maximum capacity per batch ranged up to 200kg of raw cardamom. Some planters have even provided the exhaust mechanism with a control flap at the roof. The product quality of this method of drying is acceptable. The maintenance of the traditional drying system could be done through local artisans.
The mechanical dryer for cardamom has a drying chamber fabricated with the MS angle, wooden planks and asbestos sheets. It consists of 20 small segments to accommodate drying trays of size 0.4 x 0.6 m with the MS perforated bottom in which cardamom capsules are filled. Required amount of air passes below the trays by means of a centrally located flue pipe. Heated air passes through the flue pipe to the drying trays and then to the atmosphere. Thermometers are provided in the system to record the inlet and outlet air temperatures. Wet and dry bulb thermometers are provided to record humidity. The electric heating bank consists of 600W strip finned heaters connected in such a way that 1.2 or 2.4 kw or a combination of these could be adopted to obtain the inlet air temperatures ranging from 55 to 60°c. Air flow rate could be maintained at 3.7 cubic metre per second, stated a scientist at the department of Post Harvest Technology, UAS Bangalore.
According to the scientist, the rate of moisture loss is slightly faster at the bottom. It will take 10 hours to reduce the capsule moisture content from 90 - to 10 %. However, the final moisture level is not critical as the ambient curing of the dried products makes it stable for safe packing. The colour of the cardamom capsule at harvest decides the colour of the dried product. This means the mechanical drying process does not affect the colour quality of the capsule. Also, there is no appreciable loss in volatile oil content of the capsule due to mechanical drying.
The dryer operation includes: Rinsing cardamom with water and then draining off the water. Continue drying for 12-15 hours depending on the quantity used
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