Slightly dewatered (50% moisture content) grated cassava (Manihot esculenta Crantz) mash was inoculated with Candida utilis and Geotrichum candidum – two yeasts predominant in soils from cassava processing sites in the Ogoni area of Rivers State, Nigeria – either singly or in combination. Inoculated mash was then either tied in Hessian bags or spread over pieces cut from Hessian bags and overlaid with the same material. Uninoculated samples were similarly either bagged or spread out. All samples were held at ambient temperature (30 ± 2o C) for up to 48 h. A continuous rise in pH occurred in all inoculated samples, with concomitant cyanide reduction. In all cases where inoculated mash was spread out, the pH was > 7 by 36 h, and cyanide was no longer detectable; this occurred within 24 h where the inoculum was C. utilis. For the uninoculated spread samples, an initial drop in pH within the first 12 h was followed by a continuous rise although it was still below 7 by 48 h. By contrast, there was continuous decline in pH in the bagged samples. It is proposed that aeration, brought about by spreading - rather than bagging - during cassava mash fermentation, results in alkaline fermentation, and contributes towards accelerated cyanide loss.
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