Biochemical and microbiological studies on kawal, a meat substitute derived by fermentation of cassia obtusifolia leaves

Biochemical and microbiological changes during the fermentation of leaves of the tropical legume, Cassia obtusifolia , in the preparation of the traditional Sudanese food, kawal, are reported. The microflora during fermentation were dominated by two bacteria, Bacillus subtilis and Propionibacterium sp. Other species present included Lactobacillus plantarum, Staphylococcus sciuri and two yeasts. No marked inter‐special successional pattern was observed during fermentation. Sun‐dried kawal possessed a mean crude protein content of 26.2% indicating negligible loss of N during fermentation. The overall chemical score of kawal protein was 73 with lysine as the most limiting amino acid. The main fermentation products were volatile fatty acids (VFA) principally n ‐butyric and acetic acids although propionic and isobutyric acids were also present. Total VFA content averaged 15% at the end of fermentation but fell to 10% during sun‐drying. Lactic acid concentrations remained low throughout fermentation, the final product containing only 0.2% of this compound. Accumulation of ammonia‐N closely paralleled VFA formation and similarly declined sharply in concentration during sun‐drying. The major alcohols formed during fermentation were n ‐propanol and n ‐butanol which attained a maximum combined concentration of 3% although disappearing during the drying process. The insignificant change in pH during fermentation was ascribed to the buffering effect of the high calcium content of the leaves. Changes in chemical composition noted during sun‐drying indicated that this process involved not only dehydration but secondary microbial action.