U.S. Department of Agriculture, Western Regional Research Center, Albany, California, USA.
Department of Mechanical Engineering, University of California, Berkeley, California, USA.
J Food Sci. 2024 Mar;89(3):1324-1336. doi: 10.1111/1750-3841.16963. Epub 2024 Feb 5.
Isochoric freezing (IF) at -5°C/77 and -10°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°C for 15 s followed by cold storage at 4°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. PRACTICAL APPLICATION: Isochoric freezing was used to produce carrot juice with extended shelf life. Isochoric freezing could be a beneficial alternative to conventional heat treatment for carrot juice processing as the applied pressures reached total inactivation levels of spoilage microorganisms. Moreover, the low processing temperatures better retained desirable compounds and quality attributes of fresh juice throughout its shelf life.
等容冷冻（IF）在-5°C/77 和-10°C/100 MPa 下用于保存胡萝卜汁 12 周。将其品质与经过 95°C 热处理 15 s 后再在 4°C 下冷藏的胡萝卜汁进行比较。在 12 周的时间里，等容冷冻的胡萝卜汁中原生需氧细菌、酵母和霉菌的总数仍保持在检测限以下。相比之下，经过热处理的胡萝卜汁在冷藏 3 周后开始出现微生物生长。由于类胡萝卜素的提取率增加，等容冷冻的胡萝卜汁颜色比新鲜果汁更深橙色。与热处理相比，IF 对过氧化物酶、多酚氧化酶和果胶甲酯酶的活性没有降低作用。然而，与新鲜果汁和热处理果汁相比，等容样品的类胡萝卜素含量、多酚含量和抗氧化能力更高。
等容冷冻用于生产保质期延长的胡萝卜汁。等容冷冻可以作为胡萝卜汁加工的传统热处理的有益替代方法，因为所施加的压力达到了使变质微生物完全失活的水平。此外，较低的加工温度在整个保质期内更好地保留了新鲜果汁的理想化合物和品质特性。
