Rice in India : A Status Paper

POST-HARVESTING OPERATIONS      

The post-harvesting operations of paddy crop and the storage of grains are as much important as producing the crop, because post-harvesting technology affects the quantity and quality of paddy and the finished product of it i.e. rice . If proper attention is not paid to handle the produce after post - harvesting, it may lead to a considerable loss to the producers. Generally, losses in paddy and rice during the post-harvest operations amount to about ten per cent of field production. It is, therefore, necessary to adopt proper technology after harvesting the crop for the improvement of the quantity and quality of paddy and rice.

Drying Operation    

Generally, the term drying refers to the removal of relatively small amount of moisture and it involves both heat and mass transfer operations simultaneously. Thus, drying is the process that removes moisture from the grain mass for the safe storage and preservation of quality, nutritive value and viability. In the country three methods are used for drying the paddy grains viz.

  1. Sun-drying

  2. Mechanical drying

  3. Chemical drying.

    Sun drying is a traditional method of drying the paddy grains. This practice is being followed by the farmers since very beginning of the farming history. In fact, the major quantity of produce is being dried in the country by this method.

    Mechanical drying process means drying the grains by ventilating natural or heated air through the grain mass to get it evaporated the moisture from it.

    Chemical drying method involves the spraying of common salt solution with specific gravity of 1.1 to 1.2 on the ears of the mature paddy crop. This treatment reduces the moisture content from 29% to 14.5% after four days.

Storage    

The grains are stored at three different level viz:

  1. Producer's Level

  2. Trader's Level

  3. Urban Organizational Storage Level

The method followed for storing the grains are - (i) storage in bags, and (ii) loose storage. Generally, storage in bags method is adopted in tropical regions. Storage in bags is also convenient for short term storage, where grain is intended for very early onward movement. For short term storage, no control measures against insects is needed. In loose/bulk storage method, large quantity of grains can be stored in per unit volume of space, less difficulty in loading and unloading and no investment in purchasing gunny bags. Besides, in case of bulk storage method, the infestation of insects/pests is lower.

Rice-Milling    

Before the advent of mechanical milling, hand-pounding traditional method of rice milling was in practice. With the introduction of mechanized mills, hand-pounding method has steadily decreased because it could not compete with machine mills. In fact, hand-pounding rice has got more nutritive value as compared to machine milling rice. In hand-pounding, a variety of implements are used, the more common being -

  1. Mortor and Pestle

  2. Dhenki

  3. Hand Stone (Chakki).

The conventional mills in use can be categorized into three main types -

  1. Huller mills

  2. Sheller-Huller mills

  3. Sheller-Cone Polisher mills.

After harvesting and drying, the paddy is subjected to the primary milling operation which includes de-husking as well as the removal of bran layers (polishing) before it is consumed. In this process the rice which is obtained after milling is called raw rice. An other process through which rice is obtained is called "Parboiling Rice." Nearly 60% of the total rice produced in India is subjected to parboiling. Parboiling is a hydrothermal treatment of paddy followed by drying before milling for the production of milled parboiled rice. In general, three major steps in parboiling i.e., soaking, steaming and drying have a great influence on the final characteristics and quality of parboiled rice. Parboiling of paddy has been practiced in Indian households since time immemorial. The parboiling process is followed extensively in the Eastern and part of Sourthern India, Eastern Madhya Pradesh and Uttar Pradesh. It is also well known in Western Uttar Pradesh, Punjab and Haryana in the form of Sela. Sela process of parboiling and the rice produced from this process is called Sela rice.

The rice grains are hardened sufficiently in the process of parboiling and results in improved milling properties, leading to a high head rice recovery. The parboiling process also results in the low breakage during milling. The cooking qualities of parboiled rice are somewhat different from those of raw rice. Parboiled rice takes a larger time to cook to the same degree of softness than the raw rice of the same variety. During cooking the loss of protein and starch are low. During parboiling process water soluble B-group vitamins and other water soluble nutrients get diffused into the endosperm, hence, the loss of nutrients is less in parboiled rice even after polishing than raw rice. The presence of Vitamin-'E' is also found in parboiled rice.

UTILIZATION OF BY-PRODUCTS OF RICE MILLING INDUSTRIES      

The economics of rice milling industries is largely dependent on the useful commercial utilization of its by-products. Husk, Bran and Broken Rice are the by-products of the rice milling industries. These by-products can be used in better and profitable manner both for industrial and feed purposes. The methods for the effective utilization of these-by-products are discussed below :-

Rice-Husk    

Rice husk constitutes the largest by-product of rice milling and one fifth of the paddy by weight consists of rice husk. Rice husk has a considerable fuel value for a variety of possible industrial uses. Hence, the major use of husk at the moment is as boiler fuel, wherever parboiling is practiced. Rice husk is tough because of its silica-cellulose content. The silica content in husk is the highest among plant offal. It contains 15 to 18 percent silica, therefore, it is a potent source of silica for the manufacture of silicates or in glass manufacture. Also pulverized husk is available wherever paddy is parboiled and it is mixed with other mill fractions as cattle feed. Pulverized husk has a low feed value and it has a low protein content. It contains more than 30% crude fibre. If nitrogen content in pulverized husk is increased by blending with other nitrogen rich feeds and fibre content is brought down to around 10 per cent, pulverized husk can be used as cattle feed on large scale.

Rice-Bran    

Rice bran is the most valuable by-product of the rice milling industry. It is obtained from the outer layers of the brown rice during milling. Rice bran consists of pericarp, aleurone layer, germ and a part of endosperm. Rice bran obtained during milling amounts to 4 to 9 per cent of the weight of paddy milled. True bran amounts to 4 to 5 per cent only and rest is polishing of inner bran layers and portion of the starchy endosperm.

Rice bran can be classified into three groups -

  1. Full fatted raw bran (i.e. raw bran) obtained from milling of raw paddy

  2. Full fatted parboiled bran (i.e., parboiled bran) obtained from milling of parboiled paddy

  3. De-fatted/De-Oiled bran obtained after extraction of oil from either raw or parboiled bran.

Rice bran can be utilized in various ways. It is a potential source of vegetable oil. Refined oil can be a supplementary source of edible oil. Raw rice bran contains 12-18% oil, whereas parboiled bran contains 20-28% oil. The de-oiled bran contains about 1 to 3 percent oil only. Rice bran also contains high fat and protein. It also contains vitamins, minerals and many other useful chemicals. Because of its nutritional value, it is being used as feed for poultry and livestock. Defatted/de-oiled bran contains higher percentage of protein (17-20%) vitamins (A and E) and minerals than full fatted bran obtained from raw and parboiled paddy. In fact, full fatted bran is an excellent ingredient for both food and feed.

Crude bran oil contains high free fatty acids (FFA) and is used for manufacture of soap and fatty acids. Crude oil of high FFA is refined and produced of low FFA content (about 5%) for edible purpose. Tocoferol and waxes of high melting points are the by-products of the bran oil refining industry, which are suitable for various industrial uses.

Various uses of rice bran, bran oil and its different constituents are discussed below :-

Edible Oil Grade

Bran oil contains low linolenic acid and high tocoferol, hence, it has distinct advantage over other vegetable oils. Edible oil can be produced by refining and suitable hydrogenation of bran oil. There is immense potential to increase edible rice bran oil in India. In fact, there is a vast gap between the potential and actual production of rice bran oil in India. The paddy production in India and possible availability of rice bran production and extraction of bran oil production are given below :-

There is a gap of 9.22 lakh tonnes between actual production and production potential of rice bran oil in India. This gap is mainly due to the poor milling machinery being used by millers in the country. In fact, poor rice milling machinery produce poor quality rice bran which can not be used for oil extraction economically as its oil contents is very low. If financial & technical supports are provided to the rice bran oil producers in the country, the total production of rice bran oil can be increased as estimated above. Presently, Japan is the major producer of rice bran oil. If proper efforts are made with Japan authority for technology transfer, this will help in improving the production potential of rice bran oil in India. During the year 1991-2000 the rice bran oil production has shown increasing trends in the country. Edible rice bran oil in India has not become very popular among the consumers. Therefore, a consumer awareness campaigns is required to be initiated at various level. If rice bran oil is popularized as an alternative healthy edible oils, country can reduce the edible oil imports and it could become potential substitute for import oils. This will also help the country to save the foreign exchange.

Rice bran oil is more economical than the other traditional cooking oils because while cooking it absorbs 20-25% less oil as compared to other traditional cooking oils. Besides, at the time of frying there is no much degradation of oil. The rice bran oil possesses the same frying properties as ground nut oil. Rice bran oil fries the food faster and after frying it becomes more golden brown colour resulting in lighter testing food. Food cooked in rice bran oil increases it flavour and palatability.

Industrial Grade Crude-Oil

(a) Soap Manufacture

Rice bran oil contains high free fatty acid (FFA) hence, highly suitable for manufacture of soft soap and liquid soap. Other kinds of metallic soap such as aluminium, barium and calcium soaps are also manufactured from rice bran oil and they find market as components of lubricants.

(b) Free Fatty Acid Manufacture

By hydrolysis technique of the triglycerides of fatty acids into fatty acids and glycerol, fatty acids and glycerol are obtained . The use of hydrogenation in combination with fractional distillation pure stearic and oleic acids are obtained.

Protective Coatings

From rice bran oil resin based paints, enamels, varnishes etc. are prepared.

Plasticisers

Fatty acids and fatty oil based plasticisers are used in the plastic and rubber industries.

Tocoferol

Crude rice bran oil contains 2% - 4% tocoferol and it has nutritional and antacid effect. Edible oil contains about 1% - 2% tocoferol rest is lost during deodorizing process.

Rice Bran Wax

Rice bran wax is used for coatings of candy, fruits and vegetables as it prevents moisture loss and shrinkage. It is also used as component for manufacture of carbon paper base, stencils, candles etc.

Use of De-Oiled Bran and Bran    

Feed

De-oiled/ defatted rice bran, which is a rich source of protein (17 to 20 per cent) and vitamins (vitamins A & E) is used as a cattle and poultry feed. De-oiled bran is more suitable for feed than raw bran due to higher nutritional value, higher digestibility and better keeping quality.

Food

In preparation of bakery products such as bread, cake, biscuits etc. de-oiled/defatted bran can be used as an ingredient. In baking flour, fine powder of de-oiled bran can be added up to 20%.

Fertilizer

De-oiled/ defatted bran contains plant nutrition i.e., N.P.K., and it can be used as fertilizer. Raw bran is not suitable for use of fertilizer because it contains high fat and wax, which are harmful for plants and roots.

Medicinal Use

Rice bran contains valuable Vitamin-B complexes, amino acids, phosphoric acid compound etc. and can be used in pharmaceutical industry. Protein can also be easily extracted from rice bran.

Broken Rice    

Broken rice is another by-product of rice milling industry. From the nutritional point of view, broken rice is as good as whole rice itself. Broken rice has low economic value as compared to whole rice. Generally, broken rice is of poor quality due to admixture with grit, stones and clay particles. Therefore, broken rice is used either as a part of animal feed or partially in the diet of poor people. If the quality of broken rice is improved by cleaning the paddy properly before milling, it can be utilized and marketed straightway for preparation of Idli, Dosa and other such preparation in which rice flour or wet-ground rice paste is needed.