Successfully seeking new uses for sorghum
Take one of the most well-adapted crops in Africa, add a dash of scientific enthusiasm and what do you get? The result, as recently announced at a science exhibition in London, is a whole new range of potential uses for the fifth most important cereal in the world. "It was a chance encounter with another sorghum enthusiast Dr John Taylor at the University of Pretoria in South Africa that started all this," says Professor Peter Belton of the University of East Anglia in the UK. "I'd been thinking of how to make more of sorghum for 10 years or more." Since then, his team have produced an array of foods, drinks and packaging materials. "Now there is no need for sorghum to play second fiddle to maize any more in Africa when sorghum can give us all this," he says.
One of the first priorities of the EU-funded research team was to develop new food uses for sorghum. The nutritional quality of sorghum is limited by its low content of the essential amino acid lysine. One strand of the research work has been looking at the genetic enhancement of the plant with higher lysine protein from barley. But getting more protein into sorghum is not the only hurdle. The other, and it's an ancient problem, is how to make the protein in sorghum grains - kafirin - digestible to human beings. "Traditional techniques such as malting and fermentation do go some way to improving the digestibility of the protein" explains Professor Belton. "What we have done is refine it and develop a handbook of the technique for small-scale food processors to produce porridges and other fermented food products with the highest protein possible."
The proof of any new food is in the eating, so tasting panels were set up in Kenya, Mozambique and South Africa and the testers asked to mark the new sorghum foods with either happy or frowning stickers to show their preferences. "African tastes vary widely. One of the tricks is to make sure you don't produce some 'one size fits all' product. You have to tailor the product to local taste, the local culture, the local needs." But Professor Belton has no doubt about the need for tasty, affordable and convenient meals. Africa is urbanising rapidly and the urban population has a need for ready-prepared foods and it's especially important that highly-nutritious weaning foods are available, he says. "Sorghum is a traditional weaning food, but the low protein is a problem. We've found that by incorporating fermented sorghum material into weaning food and then treating it by a process called extrusion we can produce a food which is the right thickness and has just the right amount of protein in it for growing children. In Kenya, my colleague Sam Wambugu of the Kenya Industrial Research and Development Institute has really promising products that one hopes will go to commercialisation."
The sorghum team's other breakthrough may help wean the world off its dependence on petrochemical-based plastics and packaging. "The sorghum industry in places like South Africa tends to be quite sophisticated and sophisticated industries produce a lot of waste," says Professor Belton. In the case of sorghum, milling produces bran and his team is trying to exploit that bran by taking the protein out and making plastics from it. "These plastics have the advantage that they're going to be biodegradable so they don't contribute to the huge waste problem," he says.
Sorghum protein can be made into edible, biodegradable films and coatings that could be used with fruit, vegetables and nuts exported from sub-Saharan Africa. However, experiments to date have shown that kafirin-only films are brittle, but adding glycerol and other natural plasticisers can improve film flexibility.
Science may have helped unlock the potential of sorghum for food and other uses, but now Professor Belton believes that only if these new products make business sense will that potential be exploited to the full. "One of the things that we want to do is help to create micro-industries. Because one of the ways Africa is going to grow is through the development of very small-scale industries."