MAKING SAFE FLOUR FROM BITTER CASSAVA BY INDIGENOUS SOLID SUBSTRATE FERMENTATION
Laboratory experiments showed that non-inoculated incubation of disinfected root pieces reduced cyanogenic glucoside levels, and separate inoculation with fungi and a Bacillus sp. isolated from on-farm fermented cassava caused significant additional reduction. Several of the micro-organisms involved were capable of displaying linamarase activity. However, enhanced glucoside breakdown in root pieces was associated with root softening but not with the micro-organisms' linamarase capacity. Addition of a cell wall-degrading enzyme preparation under aseptic conditions caused softening of root pieces and a significant reduction of cyanogenic glucosides, but adding linamarase did not. It is proposed that the main contribution of micro-organisms to linamarin level reduction in solid substrate fermenting cassava is their cell wall-degrading capacity which facilitates the contact between endogenous linamarase and the cyanogenic glucosides.
Inclusion of a stage of solid substrate fermentation during processing into flour appeared instrumental in reducing the potential toxicity of cassava roots and was more effective than sun-drying alone; there is room, however, for optimization to ensure safer products.