High-fiber foods: Researchers highlight nutritional quality of climate-resilient sorghum bran

18 Sep 2023 --- Sorghum bran has higher levels of essential amino acids and minerals needed for human health and development than whole grain or dehulled sorghum flour, find researchers from the University of Johannesburg. The bran also contained higher levels of crude protein, fat and fiber than whole and dehulled grain. 

Compared to whole or dehulled grains, sorghum bran is higher in calcium, zinc and potassium. The gluten-free grain contains similar protein, crude fiber, carbohydrates and minerals found in corn, wheat, rice, barley and oats. 

After identifying the nutritional quality and functional properties of white and brown sorghum, the researchers suggest that sorghum (Sorghum bicolor) bran has significant potential in the food industry and could serve as a nutritionally rich food ingredient.

“We believe that this study will have an impact on the food industry, especially toward whole grains for food product development and the use of sorghum bran as an ingredient in the development of high-fiber foods,” the study’s lead author, Dr. Janet Adebo, a researcher at the Food Evolution Research Laboratory of the University of Johannesburg, tells Nutrition Insight.

In response to the study, Monia Caramma, sustainable food researcher and steering committee member of the branch organization Sorghum ID tells us the grain has characteristics “that are currently not exploited due to the lack of knowledge of this cereal by processing companies.” 

“The application of a by-product that allows the optimization of production processes in the sustainable logic of the fight against waste. Bran is an essential food in the health market, and sorghum bran could improve the quality of gluten-free products as an essential fiber component.”

Keeping the bran 
Adebo notes that reducing nutrients in sorghum bran has become a matter of nutritional concern. She explains that bran removal, or reduction in bran particle size due to milling or deliberate dehulling, affects the nutritional quality. 

Regular whole grain consumption is linked to various health benefits in scientific studies, which, Adebo posits, is mostly associated with the bran component included in whole grain. 

Dr. Hema Kesa (left) and Dr. Janet Adebo (right) assessed the nutritional and functional qualities of sorghum bran (Image credit: University of Johannesburg).She details: “According to existing literature, sorghum is known for its health benefits, including its role in easing obesity and diabetes and reducing oxidative stress. Likewise, sorghum is gluten-free; thus, subsequent products are good for those with celiac disease.” 

“Some studies have shown pigmented sorghum (such as red or brown) to be versatile and to contain more health-promoting properties. Nutritional content seems to vary across varieties, but perhaps the red/brown could be a better option due to the additional health benefits.” 

Nutritional values
The current study, published in Heliyon, found higher crude fiber in the bran than other parts of the whole bran, at +278% for white sorghum bran and +203% for brown sorghum bran, compared to the entire grain. 

The bran also contains essential amino acids, such as leucine – 1.6 g per 100 g in brown sorghum and 1.2 g per 100 g in white sorghum – and valine – 0.8 g per 100 g in brown sorghum and 0.69 g per 100 g in white sorghum. 

Leucine and valine support repairing and building muscle tissue, while valine is also crucial in growth hormone production. 

Moreover, the researchers found relatively high calcium and magnesium levels in sorghum bran, which they note can assist in bone growth and development. 

Caramma adds that in food use, sorghum represents an essential source of iron and antioxidants that resist cooking and milling. 

“It is suitable for diets with reduced sugar content, for people with diabetes and represents an alternative to oats, corn and rice thanks to its reduced nickel content (1.4 mcg per 100 g). Thanks to this last peculiarity, it is used safely in systemic nickel allergy syndrome, which involves approximately 15% of the European population.”

The researchers caution that sorghum bran’s potential antinutrients must be investigated and reduced to ensure optimum use in food product development. They suggest further studies should explore different dehulling rates to determine how this affects composition. 

Research should look at developing food products with sorghum bran, the overall composition of these products and health-promoting constituents. 

As a climate-resilient crop, sorghum offers improved yields in arid regions.Climate-resilience 
Sorghum is currently the most important food crop after rice, corn, wheat and barley, and a critical food source for people in Africa and Asia. The grain offers improved yields in arid regions. For example, in South Africa, it is grown in drought-prone areas and is the primary source of nutrients and energy. 

Adebo explains that sorghum is known to be drought-tolerant and climate-resilient. Earlier research reported that sorghum is a “substantial contributor to food security in some of the world’s poorest regions, and literature shows that several important variables, including population growth, agricultural inputs, climate change and economic development, influence the production of this crop.”

Although the grain has gained popularity recently due to its agronomic qualities and health benefits, Adebo notes that South Africa is a net importer since “only 28,800 hectares of sorghum were planted commercially in South Africa in 2017.” 

“The Bureau for Food and Agricultural Policy predicts that South Africa will continue to be a net importer of grain sorghum through 2027,” she adds. 

The researchers expect that with a growing population in Africa, there will be a need for reliance on indigenous grains such as sorghum. 

Sustainable food researcher Caramma explains that sorghum has roots that sink deep, allowing for water savings. “It does not require nitrogenous soil with chemical fertilizers. It is as versatile as corn and can be used in the human food, livestock, biomass and cosmetic industries.” 

“Unknown to food processing industry” 
Although the market for sorghum has grown in the last eight years, according to Caramma, the cereal is still almost unknown to the food processing industry. 

“The research and development departments do not have the funds to start research on transformation techniques. Suffice it to say that attempts are made to use raw flour in the pasta and pastry sectors without considering the importance of grain size and gelatinization.” 

Sorghum can be used to develop many food products, such as pasta (Image credit: Monia Caramma).She also sees a need for more specific research on identifying the characteristics of individual varieties useful for categorizing them based on food applications.

Caramma sees the snack industry focusing on sorghum because it represents an alternative perceived as healthier even by mothers. 

“Consumers use the grain and the flour to make pancakes, wraps and small sandwiches by adding simple psyllium to the dough. The choice is mainly oriented toward a hulled product.” 

Organizing the industry 
Caramma predicts that if the food, cosmetic and health industries decide to valorize sorghum, there will be an explosion in cultivation. However, extensive technical training is required.

“Unfortunately, there is still a disconnect between farmers and processing companies. It often happens that part of the grain remains unsold or that there is a lack of organic cultivation.” 

“The sorghum sector first and foremost needs regulation from an economic point of view,” Caramma continues. “The only stock exchange is in Bologna and is not adequately consulted.” 

“Price fluctuations are such that sorghum becomes uneconomical in the food sector, especially in the presence of speculation. Coordinated action by institutions and supply chain actors, mills first and foremost, is necessary.”

By Jolanda van Hal