ABSTRACT

This study was carried out to produce and evaluate the properties of homogenized canned Ngu (African salad dressing), stabilized with two different plant based natural stabilizers (Akparata and Ofo), as well as carboxyl methyl cellulose (CMC) at various concentrations (0.0%, 0.63%, 1.25%) and sterilization time (10, 15, 20 min). A 3³ factorial response surface design was applied to generate the experimental runs for the production of the canned Ngu and the samples were subjected to the following analysis in replicates: proximate composition (moisture content, protein content, fat, fibre, and carbohydrate)  physicochemical (Vitamin A, Peroxide Value, Free Fatty Acid (FFA) and Acid Value), colour (CIE L*, a*, b*: L*:lightness, a*:redness, b*:yellowness), functional properties (Viscosity, Emulsion capacity and pH), Microbial (Total Viable Count (TVC), Total Fungal Count (TFC)), and Sensory (Taste, Aroma, Thickness, Appearance and General acceptability). The coefficient of determination (R²) which indicates the relationship between the parameters of interest and the independent variables (stabilizer, stabilizer concentration and sterilization time) of the proximate composition, colour, functional, physiochemical, microbial, and sensory characteristics of the canned Ngu ranged from 0.220(fat) to 0.7722(protein); 0.8445 (L*) to 0.8543 (b*); 0.6070 (pH) to 0.8204 (viscosity);  0.3751 (FFA) to 0.9822 (Peroxide Value);  0.1618 (TFC) to 0.4192 (TVC); and 0.9377 (Aroma) to 0.9788 (Thickness) respectively. The results showed that increase in the linear effects of stabilizer concentrations increased the scores of taste, aroma, appearance, thickness and general acceptability of the canned Ngu while a decrease occurred in the pH value. Increase in sterilization time resulted in increased peroxide value and a* value of the product but resulted in a decrease in protein value, b*value, appearance score and thickness score. The score for the thickness increased with change of stabilizer from CMC to Akparata and then to Ofo. The quadratic effect of stabilizer, stabilizer concentration and sterilization time were also evaluated and the results showed that: change of stabilizer from CMC to Akparata and then to Ofo resulted in increase in viscosity, L*, and taste score of the canned Ngu, while moisture content, thickness and general acceptability score decreased. Increase in the quadratic effect of stabilizer concentration, resulted in increase in Vitamin A, a* value, viscosity value and the taste score of the canned Ngu, but resulted in decrease in Free Fatty Acid (FFA), acid value, L* and b*, appearance, thickness, aroma and the general acceptability scores. Increase in the quadratic effect of the sterilization time resulted in increase in protein, fat, Vitamin A, emulsion capacity, pH contents of the canned Ngu while carbohydrate, peroxide value, Total viable count and b*value of the canned Ngu reduced as the quadratic effects of the sterilization time increased. This study concluded that from the optimization results, the optimum processing variables would require the use of 1.25% Ofo as stabilizer and sterilizing the emulsion for ten (10) minutes. This would give 67.0502%, 0.7881%, 3.21849%, 25.4167%, 3.66881% and 1.85186µg/100g as optimum values for moisture, ash, protein, fat, carbohydrate and vitamin A content of the product.