Enhanced extraction of beetroot peel polyphenols using response surface methodology and their stabilization in W/O/W emulsions using whey protein isolates

This study aims to investigate the bioactive compounds in beetroot peel and their stabilization in W/O/W emulsions for potential use in future food industrial applications. The extraction of polyphenols, flavonoids, and antioxidants from beetroot peels was performed with the green extraction method, and their effects were determined through spectrophotometric methods. Box-Behnken Design was used for optimizing extraction parameters and model validation. The design suggested a quadratic model for all the responses. The minimum and maximum coded values examined for the experimental design included extraction time (10-30 min), sample concentration (1-5 %), and operating power (10-50 W). The W/O/W emulsions were prepared with varying concentrations of whey protein isolates (WPI) (1 % (E₁), 2 % (E₂), and 3 % (E₃) (w/w)). The emulsions were studied in terms of creaming index, viscosity, encapsulation efficiency, antioxidant determination, color analysis, droplet size distribution, and optical microscopy on samples stored for 0, 10, 20, and 30 days at 4 °C. The optimized conditions for maximum extraction of polyphenols were 21.72 min, 4.99 % sample concentration, and 49.76 W power. The yield of total polyphenols, total flavonoids, DPPH, and ABTS activity was 46.5 mg GAE/g DW, 10.9 mg QE/g, 66.3 %, and 89.6 % respectively. 3 % (w/w) WPI provided the highest color retention, oxidative and physical stability, and encapsulation efficiency. Overall, it was observed that all the independent factors played a significant role in the extraction of phytochemicals from beetroot peel extract and could be improved to maximize model responses. The formulated emulsion has potential for utilization in future food applications.