Detoxification and nutritional enrichment of cassava waste pulp using Rhizopus oligosporus and Aspergillus niger

Abstract

The present study evaluated the detoxification and nutritional enrichment potentials of the fermented cassava waste pulp obtained through different processing methods of sweet (S) and bitter (B) cassava varieties by fermentation with Rhizopus oligosporus and Aspergillus niger. Four batches [two with both bark and cortex of the tuber removed (S- and B-), two with bark only removed (S+ and B+)] of cassava waste pulp (CWP) were produced from each of S and B varieties. CWP from the four treatments were then subjected to Rhizopus oligosporus, Aspergillus niger, and natural fermentation. Cyanide (mg HCN/kg), phytate (mg/100g), tannin (mg/100g), pH, crude protein (N X6.25) (%), ash (%), Fe, P, K and Ca (mg/100g) content of the unfermented and fermented CWP were determined using standard procedures. The range of the reduction (%) in cyanide content for Rhizopus oligosporus fermented CWP (RCWP), Aspergillus niger fermented CWP (ACWP), and naturally fermented CWP (NCWP) were 86.24 – 91.95, 79.68 – 84.34 and 72.96 – 78.58 while those for phytate were 58.82 – 71.20, 29.98 – 39.26 and 36.16 – 40.32 respectively. Fermentation had no significant (p>0.05) effect on the tannin content while the pH range of NCWP, RCWP and ACWP were 7.20 – 7.50, 5.41 – 6.40, and 3.83 – 4.21, respectively. The  range of the increase (%) in the protein content for NCWP, RCWP, and ACWP was 346 – 375 , 671 – 728 and 508 – 542  while those of the ash content were 7.16 – 7.91, 6.72 – 6.84, and 5.42 – 5.63 respectively. Of all the examined minerals, only calcium increased by 5.68 – 26.89, 49.96 - 70.43, and 59.71 – 98.87 % in NCWP, RCWP, and ACWP respectively. Results from the present study are indicating that controlled fermentation offers greater benefit over natural fermentation and that the cassava variety and not the peeling method will determine the extent of detoxification and nutrient enrichment.