Optimization of ultrasonic-assisted extraction of phenolic compounds from pomegranate and orange peels and their antioxidant activity in a functional drink

This study aimed to optimize the ultrasound extraction conditions of phenolic compounds from pomegranate (PPE) and orange peels (OPE) as agricultural wastes and use the optimized extracts to enrich a functional drink. The statistical analysis results demonstrated that the quadratic model used had high R 2 (>0.89) and good predictability of experimented results. In optimizing the extraction of PPE and OPE, the effect of three factors of extraction time (X1:10–40 min), temperature (X2: 40–70 °C), and solid to a solvent ratio (X3: 1:20–1:40 g/mL) on two responses of total phenol content (TPC) and antioxidant activity were investigated. The highest TPC (2.70 and 1.86 mg GAE/g) and antioxidant activity (72.11 and 54.27%) of PPE and OPE were obtained in the X1: 40 min, X2: 70 °C, and X3: 1:40 g/mL. No significant difference was observed between the predicted and experimental values. The results of drink tests indicated that adding PPE and OPE and increasing their levels from 10% to 15% v/v in the drinks significantly enhanced the samples' bioactive compounds content and antioxidant activity ( p < 0.05 ). The content of vitamin C (212.37 mg/100 mL) and flavonoids (83.44 mg QE/100 mL) in the drink containing 15% OPE was higher than in other samples, while the sample containing 15% PPE had the highest TPC (158.88 mg GAE/100 mL). There was a positive relationship between the level of extracts and the antioxidant activity of the drinks. During 60-days of cold storage, the content of bioactive compounds and antioxidant activity of drink samples gradually decreased ( p < 0.05 ). • Optimizing ultrasound extraction of Pomegranate (PPE) and orange peels (OPE) was done. • The functional drink was enriched by the optimized extracts of PPE and OPE. • PPE and OPE extracts were increased a functional drink's bioactive content and antioxidant activity.