An improved fermentation package for optimal detoxification of high cyanide cassava roots and peel

The fermentation process previously devised using a mixed culture resulted in slightly higher retention of cyanide in fermented roots and peel from cassava cultivars with high cyanide content. The system was therefore improved upon by introducing steps like change of steep water during fermentation, prolonging fermentation for peel and sun drying the fermented products. The efficacy of fermentation with change of steep water at every 24 h (T2) and 48 h (T3) in eliminating cyanide from roots and peel of three high cyanide cultivars (initial total cyanide 332-432 mg/kg DM as HCN equivalent in roots and 1416-1537 mg/kg in peel) was compared with non-fermented samples (T1). Total cyanide (roots) was reduced to 27-41 (T2) and 32-42 mg/kg (T3) through fermentation (72 h) while retention in nonfermented roots was 226-295 mg/kg. Bound cyanide was hydrolyzed extensively during fermentation. Fermentation (120 h) reduced the total cyanide in peel to 190-198 (T2) and 171 -218 mg/kg (T3) as against 395-596 mg/kg in nonfermented peel (T1). Fermentation followed by sun drying eliminated 90 percent-94 percent total cyanide from roots, of which 88 percent-92 percent was removed during fermentation itself. From 70 percent to 74 percent total cyanide was eliminated from nonfermented roots, of which 30 percent-36 percent only was removed during incubation and the rest during sun drying. Fermentation and sun drying removed 96 percent-97 percent total cyanide from peel of which 84 percent-88 percent was contributed by fermentation. In nonfermented peel, 89 percent-94 percent total cyanide was eliminated of which 60 percent-74 percent was through incubation and the rest through sun drying. A significant difference in cyanide removal was not obtained between T2 and T3, indicating that change of steep water at 48 h only (roots) and 48 h intervals (peel) followed by sun drying could effectively detoxify high cyanide cassava roots and peel and render them safe for food of feed use. The role of microorganisms in elaborating linamarase to help in the hydrolysis of linamarin during fermentation is discussed.