Bradbrook - 2012 - Rice Farming complete with methods to increase ric

1. Sun drying
This drying method is most common in Asia because it is much cheaper than
mechanical drying. In sun drying, the grains are spread in a thin layer (2 to 4 cm) over
a cemented or paved area that is well-aerated or windy. The grains are mixed every 1
to 2 hours. Temperature and moisture readings of the grains are taken frequently using
a thermometer and moisture meter. The grains should be protected from very high
temperatures (> 50°C) and collected or covered if it rains and at nighttime.
Grains can be bagged and stored once the moisture content goes dovm to 18%. If
longer storage is desired, the grains can be further dried using another method.
Sun drying is labor intensive and limited in capacity. It is weather-dependent and
controlling the temperature is difficult. Thus, it may take several days to get the
desired moisture content and during that time, grain losses and damage are likely to
have occurred. The quality of milled rice from sun-dried grains is generally low.
2. Heated air drying
In heated air drying, burners and fans blow warm air (40^5°C) through grains that are
either stirred manually or mechanically for even drying. The flat-bed dryer is common
in Asia and have capacities of from one to ten tons depending on its size. Small dryers
can process one to three tons of grains in six to 12 hours. In developed countries,
recirculating batch dryers have long been in use not just for rice but for other types of
grains too (e.g. wheat and barley). They are vertical-type dryers and can handle loads
of up to 20 tons. Continuous flow dryers are used by large milling companies. It has
separate sections for drying, tempering and conveying. Continuous supply of grains
for drying is necessary to justify their operation at an economically viable level.
3. In-store drying
This type of drying is widely used in Korea and, recently, in Thailand. Ambient air is
blown through the grain bulk at low velocities via air ducts in the storage bin or
compartment. This method is slow but gentle, thereby ensuring that grain quality is
maintained. Depending on the moisture content, the process can take several days to
weeks to bring down the moisture level to the desired percentage. This method is best
used in tandem with other drying methods to hasten the drying process.
To dry the gain in the shortest time that will not damage its quality, a two-stage drying