Microbiological and chemical characterisation of ting, a sorghum-based gluten-free fermented cereal product from Botswana

Fermented cereal foods produced in Africa involve a wide range of raw materials, e.g. millets, sorghum and maize, which are fermented using various microorganisms. Fermentation of these foods progresses under the influence of microorganisms and their enzyme activities. Fermentation processes differ with respect to processing technology, preparation time, and the type of raw material used. African food fermentations are largely dependent on spontaneous fermentation, or are controlled by back-slopping. These practices are often associated with inconsistent product quality and a non-reliable fermentation process. This study investigated microbiota of ting, a fermented sorghum product of Botswana, and investigated characteristic traits of lactobacilli isolated from ting. Lactobacillus reuteri and Lactobacillus fermentum; Lactobacillus harbinensis and Pediococcus acidilactici; Lactobacillus plantarum and Lactobacillus parabuchneri; Lactobacillus casei and Lactobacillus plantarum; L. harbinensis and Lactobacillus coryniformis were used as starter cultures to produce ting. All the binary strains combinations were capable of producing ting. Traditionally processed ting requires 2 to 3 days to attain a pH below 4; the starter cultures thus reduced the fermentation time to 8 h. African cereals have a high content of polyphenolic compounds, particularly sorghum and millet which reduce the nutritional value and digestibility of nutrients in these grains. Polyphenolic compounds from various sorghum varieties from Botswana were identified and the study demonstrated that microbial fermentation of sorghum by two binary strain combinations, L. plantarum and L. casei, or L. fermentum and L. reuteri affects the content of polyphenolic compound and can influence the nutritional value and antimicrobial activity of sorghum. Polyphenols have antimicrobial activities against a wide range of microorganisms and their presence in sorghum consequently influence the microbial association during fermentation and thus acting as selective agents for sorghum sourdough microflora.