A Candida parapsilosis inactivation-based UV-C process for calamansi (Citrus microcarpa) juice drink

Spoilage yeasts were isolated from ready-to-drink calamansi juice stored at room temperature. Biochemical and morphological characterizations revealed that both isolates were Candida parapsilosis. Known population of each of the two isolates was separately inoculated to freshly prepared juice drink and individually subjected to UV-C inactivation challenge. Both isolates (BC1 and SC1) exhibited a biphasic inactivation behavior, with an inactivation curve with upward concavity. The inactivation curves of both isolates had an initial inactivation lag time with minimal or no population change (7.78-14.64 s), followed by fast log-linear population decay (0.03-0.09 log CFU/s). Despite exhibiting the same inactivation behavior, the inactivation kinetic parameters of the two isolates were significantly different, with the SC1 isolate being more resistant. The inactivation kinetic parameter of the SC1 isolate was therefore used as basis for the establishment of UV-C process for the same calamansi juice drink with a lethal rate against the test organism equal to 99.999%. Application and evaluation of the process showed that the processed juice drink had sensory quality attributes not significantly different from non-processed samples. These results provide baseline information on the application of UV-C as a non-thermal processing technology for calamansi juice drink and other similar food matrices.