Dynamics of phytate-zinc balance of fungi fermented cassava products (gari and flour)

Abstract

Fungi fermented cassava products (gari and flour) were produced by fermenting cassava pulp with pure strains of some common saprophytes namely, Aspergillus flavus, Aspergillus niger, Rhizopus oryzae and Saccharomyces spp. (Baker's yeast and palm wine yeast). The phytate contents were determined by titration of 2% HCl extract of the samples against standard FeCl3. Zn and Ca were determined using atomic absorption spectrophotometry. Calculation of [phytate]/[Zn], [Ca]/[phytate] and [Ca][phytate]/[Zn] molar ratios were used in predicting the effect of phytate on zinc bioavailability. The results of the studies revealed that there was a decrease in the phytate content of fungi fermented cassava products [flour (505.6 ± 4.2−748.5 ± 2.3 mg/100 g) and gari (373.5 ± 6.2−56.7 ± 5.2 mg/100 g)] when compared to naturally fermented cassava products [flour (705.1 ± 1.2 mg/100 g) and gari (633.9 ± 3.2 mg/100 g)] and unfermented cassava products [flour (874.4 ± 3.2 mg/100 g) and gari (662.8 ± 6.5 mg/100 g)]. The calculated [Ca][phytate]/[Zn] molar ratios for the products indicated that the fungi fermentation enhanced the bioavailability of zinc from the products. Moreover, values obtained in the present study were far below the critical value of 0.5 mol/kg. This indicates that fungi fermentation would bring about a decrease in the phytate content of cassava products (flour and gari) and consequently mprove the bioavailability of zinc from the products.