The contribution of moulds and yeasts to the fermentation of ‘agbelima’ cassava dough

Agbelima, a fermented cassava meal widely consumed in Ghana, Togo and Benin, is produced by fermenting grated cassava with one of several types of traditional cassava dough inoculum. During fermentation a smooth textured sour dough is produced, the toxicity of cassava is reduced and there is a build up of volatile aroma compounds. Four types of inocula were included in the present investigation. In one type moulds were found to form a dominant part of the microbiota, the species present being Penicillium sclerotiorum, P. citrinum, P. nodulum, Geotrichum candidum and a basidiomycete. All these moulds were found to possess cellulase activity which was responsible for the hydrolysis of cassava tuber cellulose during fermentation leading to a breakdown of the coarse texture of cassava dough. The yeasts Candida krusei, C. tropicalis and Zygosaccharomyces spp. were present in high numbers in the four types of inocula including the mouldy inoculum. The yeasts C. tropicalis and some strains of Zygosaccharomyces, all of which possessed cellulase activity, were also found to contribute to the modification of cassava texture during fermentation. All yeasts and moulds exhibited linamarase activity and were therefore capable of breaking down the cyanogenic glucosides present in cassava.