About 20 per cent of the rice produced worldwide, and more than 50 per cent of the paddy produced in South Asia is parboiled.
Parboiling of paddy involves three steps namely soaking, steaming and drying. In the soaking process, the void spaces in the hull and rice kernel are filled with water and the starch granules absorb water and swell. During steaming, soaked paddy is exposed to heat for a given duration and the starch present in the rice kernel is gelatinised. Subsequently, the paddy is dried to about 14 to 16 per cent moisture content, which imparts the hardness required by the grains for milling.
"The existing methods of paddy parboiling, in which soaking and steaming operations are carried out in the same-large parboiling unit, involves a long processing time of 6-7 hrs whereas the pneumatic method reduces this time period to 2.5 hr. Traditional methods also require large amount of steam (200 kg of steam per tonne of paddy) that result in rice with a deep colour. The pneumatic parboiling method results in light colour and soft textured parboiled rice," said PVKJ Rao of ANGR Agricultural University.
The new process uses pneumatic pressure to accelerate the rate of diffusion of water into the rice kernel during the soaking treatment. The process consists of soaking the paddy at an intermediate temperature of water under pneumatic pressure and then giving steam treatment to soaked grain at gelatinisation temperature. This technique hastens the hydration rate and facilitates deeper penetration of vitamins into the grain.
Parboiling is of major importance to the world's economy and is one of the most widespread food industries in the world. The leading exporting country is Thailand followed by the United States. Parboiled rice originated in ancient India and is still popular in the region. It is being practiced in Bangladesh, Pakistan, Sri Lanka, Burma, Malaysia, Thailand, Italy, Spain, Urguay, Brazil, France and United States.
The new parboiling processing technology is the outcome of a National Agricultural Technology Project in India, which was the world's biggest World Bank assisted agriculture project.
