STUDIES ON THE EFFICIENT UTILIZATION OF TIGERNUT (CYPERUS ESCULENTUS) AS A SOURCE OF VEGETABLE OIL, ETHANOL AND ANIMAL FEED

Fresh tigernut tubers (yellow variety) were screened, washed, dried, ground into coarse powder and the powder extracted with hexane. Similarly, fresh tigernut tubers were sprouted, screened, washed, dried, ground into coarse powder and extracted with hexane. Hexane extract was filtered and solvent removed under reduced pressure affording tigernut oil in 32.63±1.31 and 36.67±0.63% yield, for un-sprouted and sprouted samples respectively. Results of physicochemical analyses of the oil confirmed that tigernut tuber is a good source of edible (vegetable) oil. Following oil extraction as above, the residue obtained was saccharified and then fermented. Three saccharification methods were investigated: enzyme, acid and enzyme/acid, respectively. The yield of ethanol produced from un-sprouted tigernut residue after oil extraction is as follows: 112±0.95 (no saccharification), 128±1.08 (acid), 176±1.26 (enzyme) and 252±1.00 (enzyme/acid) cm3 per Kg dry matter. The yield of ethanol produced from sprouted tigernut residue, after oil extraction, is as follows: 148±1.39 (acid), 184±1.25 (enzyme) and 284±1.12 (enzyme/acid) cm3 per Kg dry matter respectively. Direct fermentation of sprouted tigernut without saccharification yielded 128±1.21 cm3 per Kg dry matter. The results show that sprouting followed by enzyme/acid saccharification gave the highest yield of ethyl alcohol. The fermentation residues were analyzed for nutrients composition. There is increase in crude protein (18%), crude fibre (17%) and ash (39%), between un-sprouted tigernut flour and fermentation residue. Crude fat and carbohydrate contents of fermentation residues decreased by 28% and 42% respectively, from the un-sprouted tigernut flour. The elements copper, phosphorus, potassium, magnesium, zinc and iron showed increase whereas manganese, calcium and sodium showed decrease. The amino acids lysine,histidine, arginine, aspartic acid, glutamic acid, proline, glycine, alanine, cystine,