Utilizing By-Products in Grain and Oilseed Processing

When wheat is milled into flour, rice is polished into white grains, or soybeans are crushed for oil, the main product is just one part of the story. The husks, brans, meals, and germs left behind – collectively called by-products – represent a massive economic and nutritional opportunity. Rather than treating them as waste, the food processing industry has found ways to turn these secondary materials into valuable commodities. From rice bran oil packed with antioxidants to defatted soya flour used in emergency nutrition programs, by-product utilization is now a cornerstone of profitable and sustainable grain and oilseed processing.

What are by-products in grain and oilseed processing? 🔗

By-products are the secondary materials generated during the primary processing of grains and oilseeds. Every grain kernel has multiple layers – the outer bran, the starchy endosperm, and the nutrient-rich germ. When processors target one component (say, refined flour from wheat endosperm or oil from soybeans), the remaining portions become by-products.

In grain milling, common by-products include wheat bran, rice bran, rice husks, wheat germ, corn gluten meal, and broken rice. In oilseed crushing, the key by-products are defatted meals (soybean meal, mustard cake, groundnut cake), seed hulls, lecithin, and crude glycerin from oil refining. These materials were historically considered low-value or outright waste. Today, they are raw materials for dozens of industries – from animal feed to pharmaceuticals.

Rice bran: from milling waste to premium oil 🔗

Rice bran is one of the best examples of by-product valorization. It is the outer layer removed during rice polishing and makes up about 5-10% of the rice grain by weight. Despite being a small fraction, it is packed with nutrients – proteins, fats, dietary fibre, and bioactive compounds like gamma-oryzanol, tocopherols, and phytosterols.

Rice bran oil (RBO) 🔗

The most commercially significant product from rice bran is rice bran oil. The oil content of rice bran typically ranges from 18-25%, depending on the rice variety. RBO has a balanced fatty acid profile – roughly 22% saturated, 41% monounsaturated, and 37% polyunsaturated fatty acids – which closely aligns with the dietary fat ratios recommended by the World Health Organization. Its high smoke point (above 200°C) makes it excellent for frying, and its natural antioxidant content gives it good oxidative stability.

Globally, approximately three million tonnes of rice bran oil are produced annually. However, a significant portion of rice bran still goes underutilized – particularly in developing countries – due to the challenge of rapid lipase activity that degrades bran quality within hours of milling. Stabilization techniques such as heat treatment, extrusion, and microwave processing are critical to preserving bran quality for oil extraction.

Beyond the oil: defatted rice bran 🔗

After oil extraction, the remaining defatted rice bran still has substantial value. It is rich in protein, dietary fibre, polysaccharides, and phytic acid. According to research published in Frontiers in Nutrition, rice bran polysaccharides show anti-tumour, immune-enhancing, and blood glucose-lowering properties. Defatted rice bran is increasingly used in baked goods, pasta, noodles, and even beverages to boost their nutritional profile.

Rice hulls, another by-product of rice milling, have found use as a silica source in the ceramics and electronics industries, as fuel for biomass power generation, and as a soil amendment in agriculture.

Wheat milling by-products: bran, germ, and more 🔗

Wheat milling separates the grain into refined flour (endosperm), bran (outer layers), and germ. The bran fraction alone accounts for 13-19% of total kernel weight and is one of the most widely available agro-industrial by-products globally. Estimated annual wheat bran production ranges between 45 and 150 million tonnes worldwide.

Wheat bran in animal feed 🔗

The largest market for wheat bran remains animal feed. It is a palatable, bulky feed that provides dietary fibre, protein (14-19% on a dry matter basis), and essential minerals like phosphorus and calcium. It is widely used in compound feeds for cattle, poultry, horses, and swine. In countries like Turkey, wheat bran makes up as much as 44% of mixed feed formulations for cattle, according to Feedipedia.

Wheat bran in human food 🔗

Increasingly, wheat bran is gaining attention as a dietary fibre source for human consumption. It is used in breakfast cereals, whole-grain breads, biscuits, and other baked products. Research reviewed in the Journal of Food Composition and Analysis highlights that wheat bran consumption is linked to improved bowel function and reduced risk of colon cancer, type 2 diabetes, and cardiovascular diseases. Newer fractionation technologies can now isolate specific bran layers – such as the aleurone-rich fraction – to produce high-value functional food ingredients.

Wheat germ 🔗

Wheat germ, the embryo of the wheat kernel, is another valuable milling by-product. It is rich in vitamin E, essential fatty acids, and high-quality protein. Wheat germ oil is a premium product used in health supplements, cosmetics, and functional foods.

Soybean processing by-products: meal, flour, and hulls 🔗

Soybean crushing for oil produces soybean meal as its primary by-product – and it is arguably the most economically important by-product in all of oilseed processing. For every bushel of soybeans processed, roughly 80% of the output by weight is meal, while only 20% is oil.

Soybean meal for animal feed 🔗

Soybean meal is the world’s dominant protein source in animal nutrition. In the United States alone, approximately 48% of soybean meal goes to poultry, 26% to swine, 12% to beef cattle, and 9% to dairy cattle, with the remainder used in fish feed and pet food. Defatted soybean meal (without hulls) typically contains about 48% crude protein, making it an economical and nutrient-dense feed ingredient.

Defatted soya flour for human food 🔗

When defatted soybean meal is finely ground under food-grade conditions, it becomes defatted soya flour – a product with approximately 50% protein and less than 1% oil. According to the Food and Agriculture Organization (FAO), defatted soy flour is one of the most economical sources of edible protein available. It serves multiple functions in the food industry: it boosts protein content in breads, improves moisture retention in baked goods, reduces oil absorption in doughnuts, and extends shelf life.

Defatted soy flour is also the base material for producing soy protein concentrate (about 70% protein), soy protein isolate (about 90% protein), and textured soy protein – all of which are widely used in meat analogues, nutritional supplements, and fortified foods. In humanitarian settings, defatted soy flour is blended with cereals to create products like corn-soy blend (CSB) and wheat-soy blend (WSB), which have been distributed by USAID in emergency and development feeding programs for decades.

Soybean hulls and lecithin 🔗

Soybean hulls, removed during the dehulling step before oil extraction, are a fibre-rich by-product commonly used in ruminant feeds. Soy lecithin, separated during the degumming of crude soybean oil, is a natural emulsifier used extensively in chocolates, margarine, baked goods, and pharmaceuticals.

Other notable by-products from grain and oilseed processing 🔗

Corn gluten meal and corn steep liquor 🔗

Wet milling of corn produces corn gluten meal (about 60% protein), used in poultry and pet food, and corn steep liquor, a fermentation nutrient used in the production of antibiotics, enzymes, and other bioproducts. Corn oil extracted during wet milling is another valuable by-product.

Mustard and groundnut cake 🔗

In India and South Asia, mustard cake (the residue left after mustard oil extraction) and groundnut cake are widely used as organic fertilizer and animal feed. Groundnut cake, in particular, has a high protein content (around 40-50%) and serves as an affordable livestock feed ingredient.

Rice hull ash 🔗

When rice hulls are burned for energy, the resulting rice hull ash is rich in amorphous silica. This by-product-of-a-by-product finds use in the cement and construction industry as a supplementary cementitious material, in the electronics industry as a silica source, and in agriculture as a soil conditioner.

Economic and environmental benefits of by-product utilization 🔗

Effective by-product utilization transforms the economics of grain and oilseed processing. A mill that only sells refined flour or crude oil captures a fraction of the grain’s total value. But one that also processes bran into oil, meal into protein flour, and hulls into industrial materials can significantly increase revenue per tonne of raw material processed.

The environmental argument is equally strong. The food processing industry generates millions of tonnes of organic residues annually. When these end up in landfills, they contribute to methane emissions and soil contamination. Converting them into useful products reduces waste, lowers the carbon footprint of processing operations, and supports the principles of a circular economy in grain processing. Research from the grain fractionation sector shows that the higher the degree of value-added processing applied to by-products, the greater the economic returns – with some processed derivatives commanding 10 to 15 times the market value of raw grain.

Challenges in by-product utilization 🔗

Despite the opportunities, several challenges remain. Quality variability is a persistent issue – by-products from different batches, seasons, or grain varieties can differ in composition, making it difficult to maintain consistent product standards. Rapid degradation is another concern, especially for oil-rich by-products like rice bran, which can deteriorate within hours of milling if not stabilized immediately.

Infrastructure and technology gaps also limit by-product utilization, particularly in developing countries. Many small and medium-scale mills lack the equipment or technical know-how to process by-products into value-added forms. Market access is another barrier – even where by-products are processed, connecting producers with end-users (food manufacturers, feed companies, industrial buyers) requires established supply chains and quality certifications.

Finally, consumer awareness and regulatory frameworks need to keep pace with innovation. As by-products are increasingly used in human food (think rice bran in bread or soy flour in meat analogues), clear labelling standards and safety regulations become essential.

Innovative approaches shaping the future 🔗

Emerging technologies are expanding the possibilities for by-product utilization. Supercritical fluid extraction and green solvent-based methods are enabling cleaner, more efficient extraction of bioactive compounds from rice bran and other by-products. Bioconversion using enzymes and microorganisms can transform low-value residues into high-value products like bioplastics, bioethanol, and specialty chemicals.

Membrane separation technologies allow processors to isolate specific protein fractions from oilseed meals, creating specialized ingredients for sports nutrition, infant formula, and clinical nutrition products. Even traditional by-products are finding completely new markets – corn cob extracts in pharmaceuticals, rice hull ash in electronics, and seed meals in plant-based protein alternatives.

The trend toward biorefinery models – where a single processing facility produces multiple products from every fraction of the raw grain – represents the future of the industry. These integrated approaches maximize resource efficiency, minimize waste, and create diversified revenue streams.

Key takeaways 🔗

By-product utilization is no longer an optional add-on for grain and oilseed processors – it is a strategic necessity. Rice bran yields premium cooking oil and nutraceutical compounds. Wheat bran provides dietary fibre for human health and nutrition for livestock. Defatted soybean meal and flour power the global animal feed and food fortification industries. And newer innovations are turning even the humblest residues – hulls, husks, and ash – into commercially viable products. The processors who invest in by-product valorization today are the ones who will lead in profitability and sustainability tomorrow.

What do you think? With so many by-products available from grain and oilseed processing, which one do you believe has the greatest untapped potential for value addition? And how can small-scale processors in developing countries be supported to adopt by-product utilization technologies?

References

1. https://link.springer.com/article/10.1007/s13399-020-00846-3
2. https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2023.1287405/full
3. https://pubs.acs.org/doi/10.1021/acsfoodscitech.4c00781
4. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/wheat-bran
5. https://www.feedipedia.org/node/726
6. https://www.sciencedirect.com/science/article/abs/pii/S0889157522006482
7. https://en.wikipedia.org/wiki/Soybean_meal
8. https://www.fao.org/4/t0532e/t0532e05.htm
9. https://2012-2017.usaid.gov/what-we-do/agriculture-and-food-security/food-assistance/resources/defatted-soy-flour-commodity-fact
10. https://pmc.ncbi.nlm.nih.gov/articles/PMC11121700/