Combined treatment of cinnamon bark oil emulsion washing and ultraviolet-C irradiation improves microbial safety of fresh-cut red chard

Cationic surfactant (cetylpyridinium chloride (CPC))-based trans-cinnamaldehyde (TC) or cinnamon bark oil (CB) emulsions (TCE and CBE, respectively) were used to wash fresh-cut red chard (FCR). To enhance the washing effect, CBE (0.02% CB + 0.002% CPC) was combined with ultraviolet-C treatment (1.2 kJ/m2), and the combined treatment reduced the populations of Listeria monocytogenes and Salmonella Typhimurium on FCR by 1.29 and 1.40 log CFU/g, respectively, as compared to populations after water washing. The log reduction levels of the combined treatment against these two pathogens were higher than those of NaOCl (0.2 g/L) treatment (0.68 and 1.13 log CFU/g, respectively). After the combined treatment, the membranes of both pathogens on the red chard surface were observed to be damaged through scanning electron microscopic images. In addition, the microbial reductions by the combined treatment were maintained during storage, and sensory evaluation results showed that it did not affect the quality of the red chard. Therefore, a CBE/UV-C combined treatment can be considered a satisfactory washing method for FCR to replace chlorination.