Isochoric freezing to extend the shelf life of pomegranate juice.

Pomegranate juice was treated by isochoric freezing (-15°C/130 MPa) for 24 h and then stored under three different conditions for up to 4 weeks: 4°C/0.1 MPa, 24°C/0.1 MPa, and -10°C/100 MPa. The juice microbiological stability and quality were compared to those using heat treatment at 95°C for 15 s followed by cold storage at 4°C. Heat-treated and isochoric frozen (IF) pomegranate juice stored under isochoric conditions showed no spoilage microorganisms after 4 weeks of storage. Also, IF juice stored at 4 or 24°C for 4 weeks had lower microbial loads than those in fresh pomegranate juice. IF juice stored under isochoric conditions showed greater color stability, antioxidant capacity, and nutrient retention (anthocyanins, ascorbic acid, and total phenolic compounds) than heat-treated juices stored at 4°C. IF juice stored at 4°C also showed greater anthocyanin and ascorbic acid contents compared with heat-treated juice. PRACTICAL APPLICATION: Isochoric freezing storage at -10°C can be used to preserve the quality properties of fresh pomegranate juice. Isochoric freezing at -15°C for 24 h can also be used as a pretreatment to extend the shelf life of refrigerated pomegranate juice since the applied pressures reached total inactivation levels of spoilage microorganisms.