Quality evaluation of gari produced from provitamin A cassava (Manihot esculenta) enriched with African yam bean (Sphenostylis stenocarpa)

Abstract

Provitamin A cassava (PVAC), a biofortified yellow cassava, has great potential to alleviate vitamin A deficiency in sub-Saharan Africa. Blending PVAC with an underutilized legume, African Yam Bean (AYB), in gari production will go a long way in reducing protein and vitamin A malnutrition problems in sub-Saharan Africa where gari is a staple food. Gari was produced from PVAC mash substituted with varying proportions (0, 7.5, 15, 23 and 30%) of AYB using simplex lattice design expert (version 16.0). The gari samples were evaluated for their nutritional composition, physicochemical properties and anti-nutritional factors. Sensory attributes of the products were evaluated using a 7-point hedonic scale. Moisture contents of all the gari samples were below 5% indicating safe level for prolonged storage. Substituting PVAC with AYB at varying proportions resulted in 14.4-23.7%, 16.3-23.5%, 19.8-20.3% and 15.5-20.3% for ash, protein, calorific and beta-carotene contents, respectively, and 18.3–21.8% reduction in fiber content. Production of gari from blends of PVAC and AYB significantly (p<0.05) increased pH level and reduced total titratable acidity of the gari samples. Gari produced from 92.5% PVAC and 7.5% AYB mash had the least value of 1.20 mg/kg HCN, and 100 % cassava gari had the highest value (5.0 mg/kg) of HCN. The swelling capacity decreased with increase in the substitution level of AYB in the mixture. The results of syneresis of the samples followed a similar trend with that of swelling capacity. Water absorption capacity and reconstitution index showed increase with increase in the level of AYB inclusion. The anti- nutritional factor of the gari sample ranged from 1.95 to 5.65% for trypsin inhibitor, 4.53-31.02 mg/100g for total phenols, and 2.56-5.33 mg/100g for alkaloids. Gari produced from 100% PVAC was the most preferred in terms of colour, texture, aroma and appearance while gari substituted with 7.5% AYB was best preferred in terms of taste. Significant difference (p<0.05) was recorded for the overall acceptability attribute of 100% PVAC gari (control sample) which was best rated by the panelists. It was concluded that a substitution of 7.5% AYB into PVAC mash gave the gari with the best overall quality acceptability. These findings indicated the potential of AYB in gari processing to curb vitamin A deficiency among the vulnerable group.