Red sorghum for gluten-free diets

In Argentina, coeliac disease affects one in a hundred people. Therefore, it is the most frequent chronic bowel disease in the country. This autoimmune disease is characterized by intolerance to gluten, a protein found in cereals such as wheat, oat, barley and rye (TACC in Spanish). This affection can manifest itself at any age, it is hereditary and more prevalent in women.

So far, to counteract its effects, the only possible treatment is to go on a lifelong diet free from gluten to fix the lining of the small intestine, as this protein affects the uptake of nutrients. In spite of the current awareness of this disease and the fact that its care, clinical and epidemiological research were declared to be of national interest – Law 26,588 -, the diet for people with coeliac disease is costly. Flour without TACC is three times more expensive than the traditional one.

Professionals at the CONICET work in a research project to produce beer and flour suitable for people with this disease. For this reason, researchers use red sorghum, a very common cereal cultivated in the province of Chaco.

“We came up with the idea because we have friends with celiac disease so we wanted to produce a beer for them. This disease is usually detected late, so the problem is that these people’s palate is used to consuming beer made with barley. The different versions of this drink, especially the one made with corn, are very different in terms of colour – paler – and flavour. We began to work with red sorghum because it has tannin and it could be regulated to obtain the colour and the flavour of the traditional beer”, Elisa Benítez, assistant researcher at the Laboratorio de Química Teórica y Experimental (QuiTEx) [Laboratory of Theoretical and Experimental and Experimental Chemistry] of the Department of Chemical Engineering of the Facultad Regional Resistencia of National Technological University (UTN)

Benítez comments that the sorghum is very present in the northeast of Argentina. It is cultivated due to its resistance to extreme climatic conditions such as low rainfall and high temperature, to the attacks of birds and insects and fungal infections. This cereal is used mainly for crop rotation as it helps to recover the structure of soil and maintain its fertility. It is also used as fodder. “A tonne of corn or wheat are better paid so the cost of transportation to other provinces is justified. The sorghum, however, is available here and the cattle consume it. This project provides added value to the cereal”, the researcher adds.

The red sorghum gets his characteristic colour from its high concentration of tannin – a natural chemical substance present in some plants – which reduces the availability of proteins in the production of food. Benitez’s team studies a methodology to reduce the content of these molecules through successive extractions using an aqueous solvent. This allows the researchers to recover tannins, use them as antioxidant and also obtain a clearer grain to produce food.

Likewise, this cereal has a great number of carbohydrates which hinder the production of beer. “A high level of carbohydrates makes the beer viscous. We use commercial enzymes to reduce these levels. These enzymes degrade the starches so that the yeast can ferment them. We mainly use amylases, which degrade the starch and work well with sorghum. The production process is similar to the barley beer one but with some differences such as a longer process of maceration”, the researcher explains.

“This project is experimental but we expect to finish all development aspects by the end of the year. We have conducted some trials on the beer and improved its colour and flavour but the sensory analysis is still missing. We have performed some compositional studies and the figures are similar to the ones of the barley, but so far we have worked on the flavour and colour. For instance, we added honey to a 3 per cent and the taste is pleasant, we have to study the quantities, though. Furthermore, we aim to lower the level of tannin and concentrate it to produce coloration similar to the one of a Pale ale or lagger beer”, Benitez comments.

As regards that, the researcher says that there is another project to create a procedure to lower the tannin on sorghum, dry it and grind it to obtain flour with an improved protein level. “We can get flour with a good number of carbohydrates and proteins if we work with moisture. We have not started yet the project but it would complement the first one. The first objective was to produce beer but as it had a high level of carbohydrates, it was viscous. For this reason, we separate carbohydrates and use a portion to prepare flour with antioxidant properties due to the condensed tannins. Thus, we promote a global use of the cereal”, the scientist adds.

The production process is set to be finished in two years. During the first months, the trials are conducted and the design of the experiment is created to obtain repetitive sample values. After that, the flour is going to be produced and analysed in terms of its chemical composition. Finally, we hope to promote the development of other food products such as spaghettis, cookies or bread. This flour made of this cereal could replace the premix traditionally used to make gluten-free bread products that include rice flour, cassava starch and cornstarch, which are more expensive than the wheat flour.

“With this project we revalue a piece of raw material important for the province but without greater added value. Apart from that, it provides another option for people with coeliac disease because they could obtain flour with a lower cost than the rice one or cornstarch. This study does not only provide added value to the sorghum but also to the development of regional economies. Furthermore, it protects the environment due to the use of this cereal to improve the conditions of the soil in crop rotation”, Benitez concludes.