Viability of Chlorine-injured <i>Escherichia Coli</i> O157:H7 on Fresh-cut Cabbage during Cold Storage in High CO₂ Atmospheres

Abstract

Viability of chlorine-injured E. coli O157:H7 inoculated onto shredded cabbage was evaluated during storage in air or high CO 2 controlled atmospheres CA of 5%, 10%, and 15% at 10 and in a modified atmosphere packaging MAP at 5 and 10. When shredded cabbage was inoculated with chlorine-injured E. coli O157:H7 % injury = 65% and then stored in air or CA at 10 , counts of E. coli O157:H7 increased during storage and injured E. coli O157:H7 % injury = 34-66% were detected on samples throughout the storage regardless of the CO 2 atmosphere. When shredded cabbage inoculated with chlorine-injured E. coli O157:H7 % injury = 45-59% were stored in a MAP using either a high or low oxygen transmission permeability OTR package film, the counts of E. coli O157:H7 increased during storage at 10 and they remained constant during storage at 5. Injured E. coli O157:H7 were detected on shredded cabbage at a 54-56% level in a low OTR film at 10 and a 73-74% level in a high OTR film at 5. These results indicated that chlorineinjured E. coli O157:H7 inoculated on fresh-cut cabbage exhibited different degrees of injury during storage in a high CO 2 CA and MAP at 5 or 10 .

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

“…When an active MAP of 10% CO 2 in this study was compared with a passive MAP in our previous study (Izumi and Inoue, 2018b) , the trend of chlorine-injured E. coli O157:H7 that remained constant during storage at 5℃ were similar regardless of CO 2 concentration particularly in the first few days of storage. In high CO 2 atmospheres > 40%, Okon (1987) reported that inoculation of 10 8 CFU/mL of Azospirillum brasilense on tomato plants stimulated the respiration rate to a 1.7-fold increase as compared to noninoculated controls due to the increased activity of malate dehydrogenase related to TCA cycle in respiration.…”

“…Nontoxigenic Escherichia coli O157:H7 JCM18426 obtained from the Japan Collection of Microorganisms (Riken BioResource Center, Ibaraki, Japan) were grown in tryptic soy broth (TSB; Nissui Pharmaceutical, Tokyo, Japan) and incubated at 30℃ for 24 h. Cells were washed twice in sterile saline solution (0.85% NaCl in distilled water) by centrifugation (3,000×g, 20℃ for 10 min) , and adjusted with sterile saline solution to approximately 10 8 CFU/mL. Izumi and Inoue (2018b) reported that electrolyzed water containing 0.5 to 2 ppm available chlorine caused chlorineinjury with injury level of 46 to 90% to a pure culture of E. coli O157:H7. Thus, electrolyzed strongly acidic water was diluted to the concentration of 1 ppm of available chlorine with sterile distilled water.…”

“…a common intervention technique such as chemical disinfectant. We previously reported that chlorine-injured coliform bacteria in fresh-cut cabbage (Izumi and Inoue, 2020) and injured E. coli O157:H7 inoculated on shredded cabbage (Izumi and Inoue, 2018b) exhibited different percentages of injured cells during passive MAP storage at 5℃ or 10℃, in which CO 2 concentration ranged from 5% to 15%. In contrast, behavior of injured bacteria on fresh-cut cabbage stored in an active MAP of high CO 2 was not reported.…”

Viability of sublethally injured bacteria of fresh and fresh-cut vegetables from the field through distribution

“…Symbols with ＊ indicate significant at P ≤ 0.05 between paired low and high OTR films in the same day. CA of 5%, 10%, and 15% CO 2 at 10℃ (Izumi and Inoue 2018b) . Counts of E. coli O157:H7 increased during storage of 5 days, the increase being greater in 10 and 15% CO 2 than in air and 5% CO 2 (FIG.…”

“…We previously reported the enumeration and identification of injured bacteria by chlorine (Izumi et al 2016b;Izumi and Inoue 2018a, 2018b, 2020 , ethanol (Inoue et al 2017) , fungicide (Izumi et al 2016b) , and cold and high CO 2 atmosphere (Izumi and Inoue 2018a, 2018b, 2020 . This review is made on our published and unpublished data on the occurrence and viability of sublethally indicator and pathogenic coliform bacteria of fresh vegetables during production and harvest and fresh-cut vegetables during processing and distribution.…”