A physical stability study of whey-based prickly pear beverages

This study aimed at the development of whey-based prickly pear (WBP) beverages. Prickly pear juice and acid whey were characterized and a factorial design was used to study the effect of three factors. Four formulations of whey-based prickly pear beverages were prepared using the fractional 2^3-1 factorial design. To note, the three factors considered were whey treatment (WT) and added sugar and pectin (S and P). Two levels for each factor were tested, namely added sugar (5 or 10%), whey treatment (with or without heat treatment) and added pectin (0 or 0.05%). The turbidity percentage increase, the color-index percentage decrease, the sedimentation percentage increase, as well as the serum separation percentage were evaluated after 40 days of storage condition at 4 °C. The three factors optimization for the beverages' maximum stability were implemented by testing the main and interaction effects plots, the analysis of variance (ANOVA), the normal probability plots of standardized effects and residuals, the Pareto charts and the contour plots. The achieved results showed that the beverages were physically stabilized by sugar and HM-pectin amount increase using the heat-treated whey. Hence, regression models were suggested, which fitted the experimental data very well (R² >75% and p < 0.05).