Drying
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1. Moisture content of grain at the time of harvesting of crops is about 18 to 20 per cent.
2. Moisture content for safe storage is 14 percent for most of the crops. Drying is a process by which moisture content from grain is reduced to safe limit.
3. Drying process is basically the transfer of heat by converting the water in grain to vapor and transferring it to the atmosphere.
4. Drying is done either by using solar energy or by artificial heating. In case of sun drying, the produce is spread on hard floor or threshing yard, around 10 cm thickness, and is allowed to dry by heat supplied by the sun.
5. The produce is stirred at two hourly intervals uniform and quick drying. In general, four to five days of sun-drying is required for different produce to bring the moisture to a safe level.
6. In tropical regions, one – day drying under full sunshine throughout the day brings down grain moisture content of rice from 24 percent to 14 percent.
7. Though sun-drying is cheaper, there are some problems. The grains that are in the upper layers develop fissures due to uneven sun-drying resulting in broken grains. However, this problem can be overcome by repeated stirring.
8. Sun-drying needs large area and more labor for spreading, stirring and collection the produce.
9. Whether also may not permit timely drying.
10. With high crop intensity and period –bound varieties, crops have to be harvested even in wet season and sun-drying is difficult under cloudy and humid-filled weather.
11. High moisture in the grain as well high humidity in the atmosphere cause sprouting and moulding of grain.
12. In rice, this problem can be overcome by mixing powdered common salt at 5 kg/100kg of grain. The salt absorbs water from the grain and salt solution flows out of the heap of grain. This treatment prevents heating and subsequent damage to the produce.
13. Another way of storing wet paddy is by mixing paddy husk which helps in storage for about seven days. The produce is dried subsequently when conditions are favourable.
14. Artificial drying uses steam to dry the produce. It can be done at any time of the year, but is expensive.