Viability of chlorine-injured indicator and pathogenic coliform bacteria on fresh-cut cabbage stored in high CO₂ atmospheres

Electrolyzed water containing chlorine can induce bacteria to be in a sublethal, injured state. Sublethally injured indicator and pathogenic coliform bacteria on shredded cabbage were evaluated during storage in air or high CO₂ controlled atmospheres (CA) of 5, 10, and 15% at 10°C and in a modified atmosphere packaging (MAP) using two types of packaging (an equilibrium of 5% CO₂/15% O₂ and 15% CO₂/
5% O₂) at 5 and 10°C, using the thin agar layer (TAL) method. When shredded cabbage rinsed with electrolyzed water containing 25 ppm available chlorine was stored in a CA and MAP, coliform counts on TAL plates increased 2-3.2 log and 3-4.5 log from the initial counts during storage at 5 and 10°C, respectively, with the increase being greater in low CO₂ atmospheres. The extent of injury ranging from 24 to 87% for the coliform bacteria was detected on samples on the initial day and during subsequent storage irrespective of the CO₂ atmosphere, except for a MAP storage at 10°C. Shredded cabbage was inoculated with chlorine-injured E. coli O157:H7 (% injury = 45-65%) by using electrolyzed water containing 1 ppm available chlorine, and then stored in a CA and MAP. Counts of E. coli O157:H7 on TAL plates increased 0.5-1.4 log from the initial counts during storage at 10°C, with the increase being greater in high CO₂ atmospheres. Chlorine-injured E. coli O157:H7 (% injury = 34-74%) were detected on samples during storage irrespective of the CO₂ atmosphere and temperature. These results indicated that chlorine-injured indicator and pathogenic bacteria on fresh-cut cabbage were capable of exhibiting different degrees of injury during storage regardless of the storage atmosphere and temperature.