Biochemical and microbiological investigations of sigda--a Sudanese fermented food derived from sesame oilseed cake

Biochemical and microbiological changes during the fermentation of sesame (Sesamum inducum L) oilseed cake to produce the traditional Sudanese food sigda are reported. The microflora during fermentation was dominated by a homofermentative lactic acid bacterium Streptococcus sp, though initially, the yeasts Candida sp and Saccharomyces sp were also present. The main fermentation product was lactic acid, the concentration of which attained 50 g kg-1 during fermentation. Acetic acid was also present at levels not exceeding 15 g kg-1. No other volatile fatty acids were formed in significant quantities. The accumulation of acids led to the pH of the mixture decreasing to 4.0 after 3 days. Dried sigda possessed a crude protein content of 440 g kg-1 and retained the high sulphur amino acid content of the sesame seed cake although lysine remained the most limiting amino acid nutritionally. The sigda fermentation was quite different from that of another Sudanese fermented food kawal, prepared from Cassia obtusifolia L leaves, and was also in marked contrast to the traditional oilseed fermentations practised in West Africa with respect to both the microflora and the products of fermentation. The traditional Sudanese fermented food furundu, prepared from the seed of karkade (Hibiscus sabdariffa L), was also examined. Initial findings suggest that the furundu fermentation is intermediate in character between that of sigda and kawal. It yielded a product with a crude protein content of 270 g kg-1, the protein of being excellent nutritional value with a chemical score of 80.