Rice is among the major staple foods for more than 50% of the world’s population. India produces nearly 21% of the rice in the world, second only to China. Small-scale farmers and rice producers primarily use traditional methods for the milling of paddy. On the other hand, medium and large-scale manufacturers have shifted to modern rice milling methods that use automated heavy machinery. While both these paddy processing methods are somewhat different, both result in certain by-products. Some of these by-products can be extremely useful and nutritional, and it is essential not to throw all of this away. Through this blog, let us first understand in brief how the milling of paddy works. Then, we will discuss at length the properties and effective uses of the by-product that you get during the paddy milling process.
Milling of Paddy: Traditional Vs. Modern Method
Rice milling systems vary from home-based, traditional ones to modern, large rice processing installations. Traditional systems often include hand-pounding in a pestle and mortar, using chakkis, renting customised hullers, sheller-dehuskers, rubber rice rollers, and cone rice polishers. Modern milling of paddy is a more complex process that processes huge quantities of grains to produce higher quantities of rice, which is not achievable by traditional methods.
The unit operations of the modern method involve a step-by-step process of paddy cleaning, de-husking, separation of husk separation, then separation of paddy-brown rice, polishing, grading, sorting, weighing, and bagging. Quicker processing requires the use of lab-scale parboiling-cum-drying machinery, such as ohmic heating, microwave, hot humid air, and radio frequency. Advanced rice mill machines, such as rubber-roller shellers, vertical and humidified rice polishers, and rice colour sorters, assist with quality control, which is something that lacks in the traditional milling of paddy. After the rice milling, rice grading is done with the help of mechanical devices such as rotating graders, trieurs, plansifters, circular purifiers, colour graders, or sorters etc.
Importance of By-Products Obtained By Milling of Paddy
Based on the variety, paddy rice usually comprises ~20% rice husk (hull), ~10% bran layer, and ~70% total milled rice (also called starchy endosperm). When the milling of paddy is done correctly, it would usually result in about 20% husk, 8%– 12% bran layer based on the milling degree, and 68%–72% milled (or white) rice. During the processing of paddy rice, there is an output of minor components that include rice husk, rice germ, and bran. Unfortunately, these highly useful by-products go to waste because of a proper lack of knowledge of how to use them skillfully.
If used in an effective and profitable manner for feed and industrial purposes, these “waste products” can contribute towards the economic stability of the rice milling industry due to their commercial use. For instance, rice straw , which is another agricultural by-product, is abundantly available and can be used for livestock and biomass production.
Let us understand in detail about the different by-products of rice processing and how they can be extremely useful.
Different By-Products of the Milling of Paddy Process & How to Use Them?
There are several properties of the by-products generated during paddy processing that make them fit for various purposes.
- Rice Bran
When you mill paddy to remove the husk, what you get is rice bran – the outer brown layer. During the next stage of rice milling, this outer brown layer is removed to produce white rice. Rice bran consists of edible oil, high-quality proteins, and dietary fibres. One interesting thing to note is that though rice bran accounts for just 8% to 12% of the total weight of rough rice, it is a storehouse of nearly 90% of its nutrients and nutraceuticals. Rice bran is rich in carbohydrates, crude fat and oil, crude protein, and dietary fibres. It also contains B-complex vitamins and several minerals, such as zinc and iron.
How to Use Rice Bran?
Rice bran is a great source of edible oil, hypoallergenic protein, dietary fibre, and several nutrients vital to human life. You can use it to improve the storage stability of food due to its antioxidant properties and decrease fat absorption while frying. Moreover, it is suitable for baked products, and you can use it as a substitute for up to 20% wheat flour without hampering its quality and taste.
- Rice Husk
Also called rice hull, this by-product generated during the milling of paddy accounts for less than 20% of the paddy weight. Its major components include cellulose (28% – 38%), lignin (9% – 20%, silica (18% – 22%), hemicellulose (~28%), and ). U
How to Use Rice Husk?
Rice husk has several household and commercial uses. In India, it is usually used as boiler feed to generate steam in rice mills that produce parboiled rice. It is also used as fuel in roadside dhabas, brick kilns, or eateries. Rice husk is useful in generating electricity, producing gas that runs IC engines, and running pump sets. In the livestock industry, it is used in manufacturing soil mulch, animal feed, particleboards, and poultry litter. Risk husk is useful in the production of activated carbon, sodium silicate, and furfural, a component widely used in oil refineries, the pharma industry, and resin manufacturing.
- Rice Straw
Did you know that Asian countries are responsible for contributing more than half (~52%) of the world’s crop residue? Out of this, rice straw alone accounts for nearly 33% of the remains. Rice straw is rich in carbon with cellulose content of 32% – 47%, hemicellulose 19%–27%, and lignin 5% to 24%.
How to Use Rice Straw?
The population is growing at a faster rate, and most places are moving towards urbanisation, creating a decline in agricultural and grazing land. Rice straw holds significant potential to become a major cereal dry fodder for dairy cattle and
buffalo.
Conclusion
During the milling of paddy, whether done using traditional or modern processes, a few by-products are generated. These “waste” products, when used effectively, can be highly resourceful and profitable. Rice bran, which is rich in many essential nutrients, can be used by humans in edible forms. Rice husk has several industrial purposes. Rice straws are resourceful for the livestock industry. When used in the right way, all these by-products produced during paddy processing can contribute to the profitability of the rice industry.
