Reducing cassava toxicity by heap-fermentation in Uganda

Processing of cassava roots by the Alur tribe in Uganda includes a stage of solid substrate fermentation in heaps. Changes in cyanogen levels during the process, microflora involved, and protein levels, amino acid patterns and mycotoxin contamination of the final products were studied. Processing was monitored at six rural households and repeated at laboratory site, comparing it to sun-drying. Flour samples from rural households were analysed for residual cyanogens, mutagenicity, cytotoxicity and aflatoxins. Mean (±SD) total cyanogen levels in flours collected at rural households were 20.3 (±16.8) mg CN equivalents kg−1 dry weight in 1990 (n = 23) and 65.7 (±56.7) in 1992 (n = 21). Mean (±SD) levels of cyanohydrins plus HCN were 9.1 (±8.7) in the 1992 flours. Total cyanogen levels in the village monitored batches were reduced considerably by heap-fermentation from 436.3 (±140.7) to 20.4 (±14.0) mg CN equivalents kg−1 dry weight cassava. Residual cyanogen levels were positively correlated with particle siz...