Effect of solid state fermentation with Rhizopus oryzae on biochemical and structural characteristics of sorghum (Sorghum bicolor (L.) Moench)

Sorghum (Sorghum bicolor L. Moench) is a major cereal consumed widely in Asian and African countries as a human food, while in other countries it is consumed as a feed. Despite having an adequate nutrient content, its use in food is limited, mainly due to the content of antinutritional factors such as condensed tannins. Fermentation technology has been shown to improve the nutritional characteristics of products and help to decrease the content of these anti-nutritional compounds. The study was aimed to evaluate the effect of the solid-state fermentation (SSF) process with Rhizopus oryzae (MUCL 28168) on the chemical composition, physical-structural characteristics and nutritional value of sorghum grains. The physical structure of the sorghum starch granules was modified during the fermentation process due to the action of the enzymes, mainly amylases, produced by the microorganism. The results showed that the total carbohydrate content decreased by 1.74%, while the crude protein content increased by 23.87%. Moreover, there was an increase of 19.62% in protein digestibility. For the amino acids, some increased their concentration while others decreased it. An important result was that the lysine and tryptophan content were higher at the end of the fermentation. The fermentation process improved the nutritional characteristics of sorghum, therefore the use of sorghum can be considered for human and animal consumption.