Articles
Interrelation between viability of chlorine-injured Listeria innocua on fresh-cut cabbage and storage temperature
Article number
1442_39
Pages
293 – 300
Language
English
Abstract
Chlorine-based sanitizer can induce bacteria into a non-lethal, injured state.
We determined the effects of temperature variations (1, 5, 10, and 15°C) on the viability of sublethally injured Listeria innocua using electrolyzed water in both a broth system and fresh-cut cabbage, applying the thin agar layer (TAL) method.
In an in vitro study using a pure culture of L. innocua (7 log CFU mL‑1), treatment with electrolyzed water reduced bacterial counts by 2-3 logs and caused injury for a 33-56% level of L. innocua. When the culture of injured L. innocua was incubated at different temperatures for 72 h, bacterial counts remained below 4 log CFU mL‑1 with injured cells at a 37-61% range during incubation at 1, 5, and 10°C, whereas counts of L. innocua increased to 8 log CFU mL‑1 accompanied by a 25-40% level of injured cells at 15°C. In an in vivo study involving cabbage, shredded cabbage was inoculated with chlorine-injured L. innocua (4 log CFU mL‑1; 70-85% injury) and stored in modified atmosphere packaging (MAP) at different temperatures.
The counts of L. innocua were below the detection level (3.4 log CFU g‑1) with no injured cells detected during storage at 1°C. In contrast, bacterial counts increased to 5-6.5 log CFU g‑1 at 5-15°C, proportionally with temperature, and injured cells were detected at a 45% level only at 5°C. The MA packages approached an equilibrium of 6-10% CO2 and 5-10% O2 during storage at all temperatures.
These results suggest that storing shredded cabbage at 1°C is practical because injured bacteria persisted at 5°C and bacterial proliferation occurred above 10°C when injured pathogens adhered on fresh-cut produce.
We determined the effects of temperature variations (1, 5, 10, and 15°C) on the viability of sublethally injured Listeria innocua using electrolyzed water in both a broth system and fresh-cut cabbage, applying the thin agar layer (TAL) method.
In an in vitro study using a pure culture of L. innocua (7 log CFU mL‑1), treatment with electrolyzed water reduced bacterial counts by 2-3 logs and caused injury for a 33-56% level of L. innocua. When the culture of injured L. innocua was incubated at different temperatures for 72 h, bacterial counts remained below 4 log CFU mL‑1 with injured cells at a 37-61% range during incubation at 1, 5, and 10°C, whereas counts of L. innocua increased to 8 log CFU mL‑1 accompanied by a 25-40% level of injured cells at 15°C. In an in vivo study involving cabbage, shredded cabbage was inoculated with chlorine-injured L. innocua (4 log CFU mL‑1; 70-85% injury) and stored in modified atmosphere packaging (MAP) at different temperatures.
The counts of L. innocua were below the detection level (3.4 log CFU g‑1) with no injured cells detected during storage at 1°C. In contrast, bacterial counts increased to 5-6.5 log CFU g‑1 at 5-15°C, proportionally with temperature, and injured cells were detected at a 45% level only at 5°C. The MA packages approached an equilibrium of 6-10% CO2 and 5-10% O2 during storage at all temperatures.
These results suggest that storing shredded cabbage at 1°C is practical because injured bacteria persisted at 5°C and bacterial proliferation occurred above 10°C when injured pathogens adhered on fresh-cut produce.
Authors
H. Izumi, K. Inui, K. Satou
Keywords
injured bacteria, foodborne pathogens, shredded cabbage, modified atmosphere packaging, temperature variations
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