Role of Ultrafiltration Process in Pomegranate Juice Clarification: Quality and Rheological Indices and Bioactive Compounds

In this study, the effect of ultrafiltration membrane clarification process on quality indices, bioactive compounds and rheology of pomegranate juice was investigated. For this purpose, after clarification of pomegranate juice by classic method, the juice was treated by ultrafiltration clarification and the effect of operating parameters such as temperature (20 and 30°C) and pressure (1.5, 2.0 and 2.5 bar) on clarity, viscosity, pectin, anthocyanin, phenol, tannin and DPPH radical scavenging activity of pomegranate juice was studied. The results showed that treatments of temperature 20°C and pressure 2 bar and temperature 30°C and pressure 2 bar had the lowest (2.8%) and highest (14.3%) reduction in total anthocyanin, respectively. The treatments temperature 20°C and pressure 2 bar and temperature 30°C and pressure 2 bar had the lowest (6564 mg/L) and highest (5697 mg/L) total phenol content, respectively. The highest reduction of total tannin was observed for treatment temperature 20°C and pressure 2.5 bar (49.7%). The results showed that in all treatments, pectin amount had been reduced over 98% and also, the maximum clarity (96.5%) was observed in sample temperature 20°C and pressure 2.5 bar. In addition, the results showed that an increase in pressure from 1.5 to 2.5 bar led to a significant decrease in viscosity in both temperatures of 20 and 30°C (p < 0.05). Finally, it was concluded that treatment temperature 20°C and pressure 2.5 bar in ultrafiltration membrane clarification are suitable for pomegranate juice clarification.