Microbial and some chemical constituent changes of high cyanide cassava during simultant spontaneous submerged and solid state fermentation of "gadungan pohung"

Fermentation is one ways to reduce cyanogenic compounds in cassava. Fermentation of cassava is usually performed by submerged fermentation and solid state fermentation separately. "Gadungan pohung" is one of Indonesian traditional of cassava fermentations that combines spontaneous submerged and solid state fermentation simultantly. The objective of this study was to evaluate some chemical compound changes, microbiological profile, and cyanides reduction of three high cyanide cassava varieties during 3 days submerged fermentation and 3 days solid state fermentation simultaneously, in "gadungan pohung" processing. The resuls showed that submerged and solid state fermentation decreased most of nutritonal compounds of cassava except carbohydrate. Submerged fermentation reduced pH value from 6 to 4.5, meanwhile solid state fermentation increased pH value from 4.5 to 6. All cassava varieties revealed similar changes. Bacteria, mainly lactic acid bacteria, dominated during submerged and solid state fermentation. Yeasts were also found in higher number than molds. Cassava varieties slightly affected the pattern of microbial growth during solid state fermentation. Submerged fermentation reduced cyanide compounds. Some cyanide compounds were found in fermenting medium. Significant declined was found in cyanogenic glycosides, meanwhile cyanohydrin and free HCN increased in all cassava varieties. Solid state fermentation decreased cyanogenic glycosides and cyanohydrin, meanwhile concentration of free HCN were fluctuated during 3 days fermentation. Degradation of cyanides in solid state fermentation was due to microbial activity and increasing pH to above 5. Combination of submerged and solid state fermentation effectively reduced cyanide compounds in high cyanide cassava varieties to about 89-93%.