Sensory and microbiological qualities of romaine lettuce and kale affected by a combined treatment of aqueous chlorine dioxide and ultraviolet-C

Abstract

The effects of a combined treatment of aqueous chlorine dioxide (ClO2) and ultraviolet-C (UV-C) on the sensory and microbiological qualities of Romaine lettuce and kale were examined. Samples of Romaine lettuce and kale were artificially inoculated with Escherichia coli O157:H7 and Salmonella enterica serotype Typhimurium. The inoculated Romaine lettuce and kale, as well as fresh samples, were treated with 50 L L−1 aqueous ClO2, 10 kJ m−2 UV-C, and a combination of aqueous ClO2 and UV-C, and stored at 4 for 7 days. The combined treatment of aqueous ClO2 and UV-C reduced the initial populations of total aerobic bacteria in the Romaine lettuce and kale by 2.07 and 2.49 log CFU/g, compared to 6.36 and 6.07 log CFU/g for the control, respectively. The combined treatment also reduced the populations of yeast and mold in the samples by 1.85 and 4.25 log CFU/g, respectively. In particular, E. coli O157:H7 and S. Typhimurium inoculated in the Romaine lettuce and kale were eliminated by the combined treatment. The Hunter ‘L’, ‘a’, and ‘b’ values of Romaine lettuce and kale were not significantly different among the treatments. Sensory evaluation results indicated that the combined treatment provided better scores than did the control. Our results suggest that the combined treatment of 50 L L−1 aqueous ClO2 with 10 kJ m−2 UV-C can be useful for maintaining the microbial safety and sensory qualities of Romaine lettuce and kale.