Rice is a staple food for more than half of the world population. The world rice (paddy, unmilled) production in 2015 was estimated at 749.1 million tonne by FAO. India accounts for more than 21% of world production, ranking second only to China.
In India, rice is produced in states like West Bengal, Uttar Pradesh, Andhra Pradesh, Punjab, Bihar, Orissa, Chhattisgarh, Assam, Tamil Nadu and Haryana. The country is now self- sufficient in rice production and is also one of the leading exporters of rice in the world market. India's export of rice stood at 23.89 lakh MT in 1997-98. The corresponding value of foreign exchange earned was to the tune of Rs 3,371 crore in 1997-98. Indian Basmati rice has been a favourite among international rice buyers.
Value addition also enhances the profitability of rice production. A wide range of product development like processed and canned, ready-to-eat products, vitamin, iron or calcium enriched flaked or puffed rice, flavoured rice, starch extraction from broken rice and so on are nowadays getting popular. Value-added products from organic rice and therapeutic value medicinal rice varieties have good niche in domestic and export markets.
Rice processing
Rising food prices, infrastructure constraints in supply chain, reduction in available agricultural land, high dependency on monsoon, production technology and techniques, poor management and distribution of food commodities, efficiency and transparency of the system, and several other factors are influencing the food security scenario of the country.
India needs to invest heavily in the agriculture sector which employs almost 50% of the country’s workforce and contributes 13.7% of the GDP, including the allied sectors. If losses can be prevented by proper post-harvest management system, more grains will be available to feed more people. Due to improved technologies and activities adopted in India, the post- harvest losses of major food grains have been reduced. In rice, post-harvest losses of 11% were reported in 2004 by State of Indian Farmer-Post Harvest Management-A Millennium Study, whereas in 2010, they have been reported as 5.2 % by CIPHET (ICAR), Ludhiana, 2010.
Problem in high moisture paddy
Paddy is cultivated as double cropping system in many places. One of the crop harvests coincides with the monsoon season. After harvest since there are no efficient farm level mechanical dryers available, farmers dry the paddy in floor using solar energy but facing difficulties in the monsoon season as the floor is wet and there is continuous rain. If high moisture raw paddy is not dried to moisture level of at least 16% within two days, it leads to germination, heat development, and microbial growth followed by discolouration, musty odour development resulting in more breakage in milling. Development of farm gate suitable dryers solves the problem and reduces the loss.
Parboiling and milling
Rice milling is the oldest and the largest agro processing industry of the country. At present, it has a turnover of more than 25,500 crore per annum. It processes about 85 million tonne of paddy per year and provides staple food grain and other valuable products required by over 60% of the population. Paddy grain is milled either in raw condition or after par-boiling, mostly by single hullers of which over 82,000 are registered in the country. Apart from that, there are also a large number of unregistered single hulling units in the country. A good number (60%) of these are linked with par-boiling units and sun-drying yards. Most of the tiny hullers of about 250-300 kg/hr capacities are employed for custom milling of paddy. Apart from that, double hulling units number over 2,600 units, under run disc shellers-cum- cone polishers numbering 5,000 units and rubber roll shellers-cum-friction polishers numbering over 10,000 units are also present in the country. Further, over the years, there has been a steady growth of improved rice mills in the country. Most of these have capacities ranging from 2 tonne /hr to 4 tonne/ hr. At present, over 1,30,000 rice mills are available in India including modern rice mills.
Parboiling
Parboiling is a hydrothermal treatment in which paddy is soaked in water and steamed to get gelatinised rice. Due to parboiling, the rice gets harder and results in higher milling yield with lesser breakage and more oil content in bran. Besides it also contains more vitamins and minerals in polished rice. Different methods of parboiling are in vogue which include household parboiling, single steaming, double steaming, hot water soaking and steaming. The disadvantage in single steaming is longer soaking time which causes off smell in rice. In conventional rice mills, usually follow single or double steaming method whereas modern rice mills adopt hot soaking method. In modern rice mills, after parboiling, the paddy is dried in mechanical driers.
Milling
Rice milling is the process of removing the husk and part of the bran from paddy in order to produce edible rice. Unlike other food grains, rice is mostly cooked and consumed in whole form. Milling technology is therefore geared to obtain maximum out-turn of milled rice and to reduce breakage to the minimum. Rice milling systems range from the home-scale to the large, complex modern rice-processing installations. They include hand-pounding pestle and mortar, huller, emery sheller-cum-huller mills, emery sheller-cum-cone polisher mills and the modern rubber-roll sheller-cum-vertical emery polishers.
In modern rice mills, the husk is removed first in rubber roll sheller followed by polishing in abrasive emery polishers or friction metal polishers. Polishing is done in two to three stages. Raw paddy milling in steel huller mill results in low milling recovery of around 50 - 54 % with more broken. The recovery of whole rice in a traditional rice mill using steel hullers is around 62-67%. Against it, the recovery percentage of whole rice in modern rice mills using rubber roll shellers and emery polishers is around 68 -70% in case of milling of parboiled paddy. Further the quality of rice bran obtained in modern rice mill is better with higher oil content..
Modern rice mill
The concept of modern rice milling is essentially to remove the husk separately from paddy and then bran to produce polished rice. The unit-operations are cleaning, destoning, dehusking, husk separation, paddy-brown rice separation, polishing in stages, grading, silky / humidified polishing, sorting, weighing and bagging. The ultimate cause of rice breakage during milling is the defects in grain. Maintaining good grain quality by proper harvesting, drying and storage practices is therefore of greatest importance for reducing rice breakage. But the type of mill, the moisture content and the grain size and shape are also important.
Value addition of rice
Normally the farmers after harvest sell their product to traders without any further processing. Even a mere primary processing like cleaning and grading will give higher price to the farmers. Further value addition like preparation of brown rice, puffed rice, flaked rice, ready-to-eat foods and extruded foods will increase the income.
Brown rice
It is highly nutritious, however, due to drudgery in preparation by hand pounding it is not popular even though it is traditionally used. Nowadays suitable machineries are available. Brown rice from traditional and organically grown paddy has more commercial value. For getting brown rice, it has to be milled in rubber roll sheller to remove husk followed by unshelled paddy separation.
Puffed rice
Normally puffed rice is prepared by immediate immersing the sand roasted paddy in water, water drained, tempered, dried and milled. The polished rice is treated with solution of salt, sugar, soda salt and puffed in sand medium. From the puffed rice, ready-to-eat products like snack foods can be prepared.
Flaked rice
It is another form of nutritious and quick cooking product from rice. In the production of flaked rice, more losses occur due to more powdering. Soaked paddy is roasted and flaked in edge runner or roller flakers. Technologies are available for preparation of ready-to-cook lemon bath, curd bath, and so on and it has more export potential.
Other products
The flour from rice or broken can be used for various products like murrukku, puttu, noodles, idiyappam and so on. Rice sevai with different tastes will add the value. Rice flour can be used for preparation of extruded rice. As it is an extruded product with same rice shape, it can be used as ready-to-eat form with different flavours. Another important advantage is fortification with minerals and vitamins.
Traditionally value-added products are available. But it is labour-intensive and the products have lesser shelf life. Development of automatic or semi-automatic machineries with hygienic way of preparation, ready-to-serve and with more shelf life is required for commercial exploitation.
