Benefits of isochoric freezing for carrot juice preservation

Isochoric freezing (IF) at -5 degrees C/77 and -10 degrees C/100 MPa was used to preserve carrot juice for 12 weeks. The juice qualities were compared to those using heat treatment (HT) at 95 degrees C for 15 s followed by cold storage at 4 degrees C. The native population of total aerobic bacteria, yeasts, and molds in isochoric frozen juice remained below the detection limit for 12 weeks. In comparison, microbes started to grow in heat-treated juices after 3 weeks of refrigeration. The color of isochoric frozen juice appeared more deep orange than the fresh juice due to an increase in carotenoid extractability. IF was not effective in reducing the activities of peroxidase, polyphenol oxidase, and pectin methyl esterase compared with HT. However, the isochoric samples showed higher carotenoid content, polyphenol content, and antioxidant capacity compared to the fresh and heat-treated juices.