Effect of harvest age of cassava roots and sweet potato tubers on alcohol yield

Several studies have been conducted in the past using cassava and sweet potato as feedstock to optimise the yield of alcohol. Harvest age of cassava and sweet potato may have some effects on the fermentable carbohydrates quantity. This study aims to establish the best harvest age of cassava and sweet potato for alcohol production. Two varieties of cassava (Sika bankye and Ampong) cultivated and harvested at 8, 10 and 12 months and two sweet potato varieties (Apomuden and Tuskiki) harvested at 3, 4 and 5 months were used for the study. Starch hydrolysis was performed with two sets of enzymes followed by fermentation with Bio-Ferm XR (Lallemand) yeast. The nutrients in Sika bankye were generally higher than in Ampong, except for ash. Sika bankye had the highest alcohol yield (14.8% v/v) between the two cassava varieties, with the best harvest age of cassava for ethanol production being 10 months. Apomuden had relatively higher nutrients than Tuskiki at all levels of growth except for fat. Apomuden had the highest alcohol yield (15.7% v/v) between the two sweet potato varieties with 3 months being the economical harvest age of sweet potato for ethanol production.   Key words: Cassava, sweet potato, harvest age, saccharification, fermentation, alcohol yield.