Quality Assessment of Powdered Maize Ogi Fortified with African Walnut (Tetracarpidium conophorum) Flour

Abstract

Protein deficiency of fermented cereal gruel popularly known as ogi (akamu) is a justification to fortify it with African walnut. In this study, powdered maize ogi and walnut flour in the ratio 100:0; 90:10; 80:20 and 70:30 labelled AZ, BY, CX and DW, respectively were formulated. Sample ‘AZ’ served as the control. Microbiological analysis, proximate composition, and functional properties of the composite flour samples were determined using Standard methods. Sensory evaluation of ogi porridge prepared using the flour samples were carried out using 9-point Hedonic scale. Total heterotrophic bacterial and fungal count of the flour samples were within the range of 7.01-7.41 and 4.23-4.45 log10CFU/g, respectively. The frequency of occurrence of bacterial isolates from the flour samples include Corynebacterium spp. (27%), Micrococcus spp. (14%), Lactobacillus spp. (13%), Citrobacter spp. (13%), Pseudomonas spp. (13%), Bacillus spp. (13%) and Streptococcus spp. (7%) while the fungal isolates were Aspergillus spp. (45%), Rhizopus spp. (22%), Geotrichum spp. (22%) and Mucor spp. (11%). All the proximate parameters and functional properties of the flour samples showed significant differences (p<0.05) with the exception of protein content and bulk density, respectively. Sample ‘AZ’, ‘BY’, ‘CX’ and ‘DW’s protein content is 0.88±0.08%, 1.14±0.20%, 1.23±0.27% and 1.31±0.38%, respectively. The lipid content (2.00±0.75 - 15.20±0.61%), ash content (0.40±0.06 - 0.90±0.04%), emulsion capacity (2.98±0.14 - 5.62±0.17%), bulk density (0.56±0.06 - 0.61±0.06 g/ml), and swelling index (1.99±0.10 - 18.89±0.21%) of the flour samples increased as the level of walnut flour substitution increased with few exceptions. In contrast, other proximate parameters, gelatinization temperature (75.6±0.48 - 82.4±0.58 oC), water absorption (2.60±0.11 - 3.35±0.35 g/g) and oil absorption (1.56±0.06 - 1.80±0.08 g/g) capacity of the flour samples decreased with few exceptions. Although ogi porridge made from ‘BY’ is more desirable than using other fortified flour formulations, ogi porridge made from ‘AZ’ was assigned the highest score for all the sensory attributes except appearance. Interestingly, ogi porridge prepared using maize ogi flour fortified with walnut flour and 100% maize ogi flour were generally acceptable.