Viability of sublethally injured indicator and pathogenic coliform bacteria on fresh-cut cabbage during storage in an active MAP of 10% CO2.

Abstract

Shredded cabbage treated with either tap water or electrolyzed water was stored in an active modified atmosphere packaging (MAP) of 10% CO2 for 5 d at 10℃, 7 d at 5℃, and 8 d at 1℃ to evaluate the occurrence and viability of sublethally injured coliform bacteria. The CO2 and O2 concentrations in the packages approached an equilibrium of 10% CO2 and 10% O2 during storage at all temperatures tested. Coliforms in shredded cabbage increased during storage at all three temperatures, with the increase being greater at 10℃. Sublethal injury at 65% to 69% for the coliforms was detected only on cabbage samples treated with electrolyzed water and stored at 5℃ for 4 and 7 d. Enterobacter cloacae was one of the injured species of coliform bacteria in shredded cabbage. Shredded cabbage was inoculated with chlorine-injured Escherichia coli O157:H7 and stored at 5℃ for 6 d in an active MAP of 10% CO2. Counts of E. coli O157:H7 remained almost constant during storage, and injured E. coli O157:H7 ranging from 50% to 70% were found on shredded cabbage throughout the storage period. These results indicate that sublethally injured indicator and pathogenic bacteria would be found on fresh-cut cabbage in the realistic MAP storage at 5℃.