Effect of enzymatic treatments and microfiltration on the physicochemical properties and antioxidant activities of two Tunisian prickly pear juices

Prickly pear has attracted domestic and international industries’ attention owing to its nutritional and health benefit potentials. However, consumption of prickly pear juices is limited by many factors which are addressed essentially through processing methods. The purpose of this study was to compare the effect of clarification by pectinolytic enzymes of Penicillium occitanis coupled with microfiltration (MF) on the physicochemical properties and antioxidant activities of prickly pear juices. The juices were treated with various enzyme concentrations (0.5–5 U/mL), at different times (10–40 min) and temperatures (35–65 °C). The effect of these enzymatic treatments on the viscosity of juices was evaluated using a central composite design. The optimum conditions for the clarification of red fruit juice (RFJ) and green fruit juice (GFJ) were obtained based on surface and contour plots. The optimal treatment conditions were as follows: enzyme concentration 4.75 U/mL, time 37 min and temperature 55 °C for RFJ and enzyme concentration 4.65 U/mL, time 35 min and temperature 55 °C for GFJ. The experimental value of viscosity of the two prickly pear juices was reduced by 34.1% and 30%, respectively which was closely linked to the predicted value (31.79% and 28.93%, respectively). Higher permeate flux and better juice quality were achieved after the enzymatic treatment. The total phenolic and flavonoid contents were correlated with the antioxidant activities. During three months of storage at 4 °C, the clarified juices were microbiologically safe. Our findings showed that the combined pectinolytic enzymes-MF process can be considered as a promising technique that satisfactorily preserves the juice quality.