Effect of an UV-C Light-Based Hurdle Strategy for Carrot-Orange Juice Processing on Candida parapsilosis Inactivation and Physiological State: Impact on Juice Sensory and Physicochemical Quality Parameters

Abstract

In the past two decades, novel preservation technologies have been investigated to achieve sufficient microbial reduction while improving the quality of food and beverages. The effect of UV-C light (UV-C, 1720 mJ/cm2) assisted by mild heat (H, 50 °C) on the inactivation and the physiological state of Candida parapsilosis ATCC 22019 in a carrot-orange juice was studied by flow cytometry. Additionally, the juice samples processed or not (control) by the single (UV-C; H) and combined (UV-C/H) treatments were analyzed for total polyphenol content (TPC), total antioxidant activity (TAA), color, turbidity, °Brix, pH, and pectin methylesterase units (PME) along 13–24-day storage (4 °C). Consumer-profiling studies were conducted on UV-C/H and a pasteurized juice. UV-C/H was highly effective in reducing C. parapsilosis by 5.5 log cycles, whereas the single UV-C and H treatments induced 2.9 and 3.9 log reductions, respectively. Flow cytometry revealed a shift with time from cells with intact membrane and esterase activity to those with permeabilized membrane and without esterase activity, which was significantly higher for UV-C/H samples (98.0%) compared with the single treatments (12.0–46.2%). UV-C/H preserved juice color, pH, °Brix, and turbidity of the juice, which exhibited equal TAA (0.7 mg/mL) and higher TPC (302.1 μg/mL) than the control (TAA = 0.7 mg/mL/TPC = 205.0 μg/mL), remaining constant throughout storage. PME decreased 42–45% for the H and UV-C/H treatments, respectively. A cluster sensory analysis revealed that one group of consumers showed a remarkable interest in the UV-C/H juice, while the conjoint study showed that it was perceived as very healthy. The CATA question determined that the UV-C/H processing prevented the juice from being perceived too particulate or with cooked or artificial taste, as happened with the pasteurized juice.