The small bran with a big nutritional punch

Researchers from the University of Johannesburg have found that sorghum bran has higher levels of essential amino acids and minerals needed for human health and development than a whole grain or dehulled sorghum flour.

According to the research, sorghum bran is higher in calcium, magnesium, leucine and valine than whole grain flour. The grain is also climate-resistant and gluten-free, thus holding its own on macro and micronutrients compared to the biggest grains produced worldwide.

The researchers — Dr Janet Adebo and Dr Hema Kesa — investigated and compared the nutritional quality and functional properties of the different anatomical parts of two locally available sorghum varieties, white and brown sorghum.

According to Adebo, the reduction of nutrients in sorghum bran through bran removal or hulling has become a matter of nutritional concern.

“There is strong scientific evidence linking regular consumption of whole grain cereal foods to long-term health benefits. The studies mostly associate this with the bran component included as part of whole grains,” she said.

Sorghum is grown both as a traditional and commercial crop for humans and animal food in Africa and Asia. It is one of three gluten-free grains in the top seven grains produced worldwide.

In developing countries, the grain has the added advantage of being produced locally, as it is known for its high resilience during water scarcity.

It is traditionally made into porridge, flatbreads, beer and cakes. In industry, it is known as sorghum offal, sorghum milling waste or sorghum mill feed.

In consumer foods, it is used as an additional ingredient in the development of high-fibre snacks, baked products, chocolate and pasta.

Fibre

Crude fibre in the bran samples Adebo analysed were much higher than from other parts of the whole grain. Compared to the whole grain, white sorghum bran had 278.4% higher crude fibre and brown sorghum bran had 203% higher crude fibre.

Leucine

Brown sorghum bran contained high levels of the essential acid leucine, above the recommended daily allowance (RDA) level. The levels detected in the brown sorghum bran were up to 1.60 g/100 g.

The bran could help supply this essential amino acid required for repairing and building muscle.

Valine

High amounts of up to 0.80 g/100g valine were detected in the brown sorghum bran.

The essential amino acid valine is vital for muscle tissue and repair as well as growth hormone production — much of these functions are needed in kids and teenagers who require these essential nutrients.

Calcium and magnesium

Relatively high calcium and magnesium levels were detected in sorghum bran. The results show that sorghum bran is a cheap and readily available source of these minerals which can assist in bone growth and development.

The analysis found 1020.91 mg/100 g calcium and 292.25 mg/100 g magnesium in brown sorghum bran.

In white sorghum bran, the results show 995.17 mg/100 g calcium and 226.02 mg/100 g magnesium.

Crude fat

Relatively high levels of fat in the bran could potentially open a market for sorghum bran oil — a ‘plant’-based oil.

The crude fat was higher in both bran samples, as compared to other anatomical parts of the sorghum grain.

Compared to the whole grain, white sorghum bran had 120.7% higher crude fat and brown sorghum bran flours had 81.3% higher crude fat.

According to Kesa, sorghum held up well with macro-nutrients when compared with top grains worldwide such as corn, wheat, rice, barley and oats. It contained similar ranges of protein, crude fibre, carbohydrates and minerals.

“Sorghum has a relatively low glycaemic index (GI) compared to some other grains. Foods with a lower GI can help regulate blood sugar levels, which is particularly important for people with diabetes,” Kesa said.

The study is published in Heliyon.

Image caption: Dr Hema Kesa (left) and Dr Janet Adebo (right). Image credit: Therese van Wyk, University of Johannesburg.