Inactivating E. coli

Fresh lettuce can be contaminated with foodborne pathogens at farm by manure and irrigation water. Lettuce, as a minimally processed and ready-to-eat food product, can act as a vehicle for transmitting foodborne disease. Spray washing is a common sanitizing method for the fresh produce industry. UGA food scientists investigated the antimicrobial effect of spraying slightly acidic electrolyzed water (SAEW) and a combination of ozonated water with ultraviolet light in reducing Escherichia coli O157:H7 on romaine and iceberg lettuces. The combination of UV and ozonated water treatment had significant higher reduction than either UV or ozonated water treatment alone. The synergistic effect of UV and ozonated water combination treatment may be due to ozonated water plus ozone gas released from ozonated water that can get to the folded leaves where UV-C light was not able to reach. In the current study, lower antimicrobial efficacy on iceberg lettuce than romaine lettuce for SAEW may be because SAEW cannot reach or penetrate into the stomata on iceberg lettuce where the bacterium was internalized. However, for UV-ozonated water combination, UV can stimulate the opening of the stomata, allowing ozonated water or ozone gas to inactivate bacteria that may be internalized in the stomata.