Characterization and optimization of Casimiroa (Casimiroa Edulis) fruit juice using Response Surface Methodology (RSM)

Background: Casimiroa edulis fruit is an underutilized seasonal fruit of Ethiopia, is a rich source of many medicinal and nutritional properties. The fruit is found in different parts of the country, Ethiopia. However, there is no clear research evidences of the fruits on post-harvest handling, preservation, processing, and value addition. Purpose of the study: The present study is aimed at the characterization, optimization of enzyme assisted casimiroa fruit juice clarification process based on selected quality parameters of the final product. Methodology: D-Optimal Mixture Design and RSM were used to investigate level of ingredients and the effects of independent variables on physicochemical composition, functional properties, mineral values and acceptability tests of casimiroa fruit juice. Graphical and numerical optimization were conducted to find the best variables conditions. Casimiroa fruit was treated at various enzyme concentrations (0.01-0.2%), incubation temperature (30-55oC) and incubation time (30-100 mini.) of treatment. A second order Central composite (CCD) was employed to identify the effect of independent variables on the final product. Results: In this study, a statistical significant difference (p < 0.05) was observed within the process variables on nutritional profiles of casimiroa fruit juice. Furthermore, the enzyme treatment reduced the cloudy appearance of casimiroa fruit juice and improved the clarity of juice. The coefficient of determination, R2 values for the dependent variables were almost greater than 0.8. This study revealed that, clarity, viscosity, TSS, TA, pH, phenolic compounds, flavonoids, β-carotene, ascorbic acid, Na, K, Ca, Fe, Zn, P and overall acceptability were significantly (p < 0.05) correlated to incubation temperature, incubation time and enzyme concentration. Incubation time and enzyme concentration were the most important factors affecting the characteristics of the casimiroa fruit juice as it exerted a highly significant influence (p < 0.05) on the dependent variables. Conclusion: In conclusion, enzyme-treatment improves qualities of fruit juice and the overall optimization suggests that enzymatic-treated juice made with 75% fruit pure, 21.25% water, 2.63% sugar and 1.13% citric acid with process variables of incubation temperature (44.01oC), incubation time (62.74 min.) and enzyme concentration (0.2%), respectively achieved the best formulation for this combination of variables with a desirable of 0.9029.