Modelling the Color and Microbial Properties of Canned Ngu by Response Surface Method

Abstract

Background: Ngu is an African salad dressing used to improve the stability and shelf life of African salad. The aim of this study was to produce canned Ngu using three stabilizers at various concentrations, constant sterilization temperature, and varied sterilization times. Methods: Ngu (50 L) was prepared from potash using three stabilizers at various concentrations. A three-level factorial response surface design was applied to generate the experimental runs for the production of the canned Ngu. The Ngu emulsion was filled inside 250 ml bottle jars, sterilized at 121 oC at various times, and canned. The color of the canned Ngu was evaluated using the Comission Internationale de l'Eclairage color scale, and its microbiological attributes, Total Viable Count (TVC) and Total Fungal Count was determined with standard procedures. The effect of the stabilizers (Akparata, Ofo, and Carboxyl Methyl Cellulose), stabilizer concentration, and sterilization time on the color and microbial properties of the canned Ngu was assessed. The Statistical Software Design Expert version 8.0.7 was utilized for response surface analysis and derivation of model equation. Results: Increase in sterilization time increased the a* value and decreased the b* value of the canned Ngu. The quadratic effect of stabilizer, stabilizer concentration, and sterilization time indicated that the alteration of stabilizer from Carboxyl Methyl Cellulose to Akparata and then to Ofo increased the L* value, of the canned Ngu. An increase in the quadratic effect of stabilizer concentration increased the a* value but decreased the L* and b* values of the canned Ngu. However, the TVC and b* value of the canned Ngu reduced as the quadratic effects of the sterilization time increased. Conclusion: Total Fungal Count and TVC value of all the canned Ngu samples were within acceptable limits, ensuring the samples safe for human consumption.