COMBINATION EFFECT OF UV-C LIGHT AND OZONE FOR THE INHIBITION OF LISTERIA SPP. ON GALA APPLES SURFACEPhan Le Bao Ngoc and Patimakorn Pasuwan
This study investigated the effectiveness of ultraviolet-C (0.96, 1.92 and 2.88 kJ/m2) and 1.7 ppm gaseousozone with different exposure time (5, 10 and 15 minutes) on the behavior of Listeria species (Listeriamono cytogenes serotype 4b, Listeria monocytogenes serotype 1/2a, atypical Listeria innocua and cocktail of Listeria) on Gala apples surface and to observe the recovery of these bacterial pathogens on treated apple after 6 days of storage at 12ÂºÂ±1. Results indicated significant reduction of Listeria spp. population. Ozone treatment alone only showed the significant disinfection on Listeria treatments (except L. monocytogenes 4b)with the longest exposing time treatment (15 minutes), got 1.1-, 0.9- and 1.8- log count reduction on L.innocua, L. monocytogenes 1/2a and cocktail, respectively. The inactivated efficiency on Listeria treatment was most significant improved by combination of UV-C 0.96 kJ/m2 and gaseous ozone with 15 minutes exposing, resulting in 5.1-, 3.6-, 4.4- and 4.2- log count reduction with L. innocua, L. monocytogenes 1/2a, L.monocytogenes 4b and cocktail, respectively. After 4 days storage (12ÂºÂ±1) with treated samples, the microbial reductions were observed for all storage treatments from 1 log N/N0 to 4.5 log N/N0 (N: the microbiale numeration after storage time, N0: the microbial enumeration after UV-C and ozone treatments), indicating that a residual antimicrobial effect of UV-C and ozone was been continuously during storage. In conclusion,the combination of UV-C and ozone could be an appropriate treatment considering as safe, friendly and cost-effective method to control the survival of Listeria spp. as well as its regrowth ability on fruits surface after treating.
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