Comparative Study of the Microbial Stability and Quality of Carrot Juice Treated by High-Pressure Processing Combined with Mild Temperature and Conventional Heat Treatment

High-pressure processing at mild temperatures (HPMTs) could be an alternative to thermal processing for destroying pressure-resistant bacteria and achieving commercial sterilization. In this study, carrot juice was pressure-treated at 300, 400 and 500MPa for 15min at 40, 50 and 60C, and afterward stored at 4, 25 and 37C. The results showed that 400-500MPa/50C and 300-500MPa/60C-treated samples had a shelf life of 28 days at 4C, lasting just as long as heat-treated samples. HPMT reduced peroxidase activity to 16-50%. The vitamin C content of the HPMT-treated samples was 28.7-60.7% higher than that of the heat-treated samples. HPMT conditions, except 500MPa/60C, preserved lightness (L*) and redness (a*) better than heat treatment (P<0.05). Carotenoid was stable under both HPMT and heat treatment. Sensory analysis indicated that the HPMT-treated samples were more acceptable to consumers than heat-treated samples. It can be concluded that the HPMT parameters of 400-500MPa/50C and 300-400MPa/60C showed comparable effects on microbial stability at 4C and better quality preservation performance than heat treatment. Practical ApplicationsHigh-pressure synergetic technologies are a research hot spot in the nonthermal sterilization field and are expected to find application in food processing as an alternative to thermal sterilization. It is necessary to assess the performance of this novel technology in terms of microbiological stability and quality preservation. In practice, processing parameters should be explored to ensure that the treatment not only kills microorganism effectively but also retains the quality of the food as much as possible. This study suggests some processing and preservation conditions for carrot juice demonstrating the advantages of high-pressure processing at mild temperature over traditional thermal sterilization, which will be of benefit to the fruit and vegetable juice industry.