Fermentation in cassava (Manihot esculenta Crantz) pulp juice improves nutritive value of cassava peel

Abstract

A major challenge in using cassava peels as a source of feed for animals is the presence of cyanogenic glycosides and the low concentration of protein. Cassava pulp juice was squeezed out of grated cassava pulp and fermented for 3 days at ambient temperature. The microorganisms in the fermented pulp juice were identified as Aspergillus niger, Aspergillus flavus and Lactobacillus spp. Non-sterile cassava peels were sun-dried, milled, and inoculated with fermented cassava pulp juice over a 7-day period. Controls were treated with either sterile distilled water, autoclaved inoculum or phosphate buffer (pH 5) over the same period. After 7 days, the cyanogenic glycoside content of the peels, determined by the silver nitrate titration method, had decreased to 12.3% (p<0.05) of the value for untreated peels while the cyanogenic glycoside content of the controls 38.8 - 42.9%. Proximate analysis of 7-day inoculum-treated and untreated cassava peels showed that the protein content of the treated peels had increased 10-fold, and significant decreases in starch and fat content were recorded. The fibre content remained unchanged. The present findings show that microorganisms present in fermented cassava pulp juice are capable of enhancing the nutritional value of cassava peels by increasing the protein content and reducing the cyanogenic glycoside content to levels safe for consumption by livestock.