Behaviour of Listeria monocytogenes and autochthonous flora on meat stored under aerobic, vacuum and modified atmosphere packaging conditions with or without the presence of oregano essential oil at 5 oC

The provision of plentiful good-quality food is a primary issue in the modern world. This work was planned to study the influence of packaging atmosphere and oregano (Origanum vulgare) essential oil addition [(vacuum packaging: T1 or modified atmosphere packaging or T2 (CO2/N2 = 4:6) or T3, T2 with oregano essential oil (T2 + EO)] under various storage temperatures (0, 5, 10, and 15 °C) on the control of survival of Escherichia coli O157:H7 and associated spoilage flora in sliced smoked turkey meat. The pathogen increased by only <1.0 log colony-forming unit (CFU)/g under all packaging and temperature combinations. Moreover, T1, T2, and T3 exerted practically similar inhibitory activity against the pathogen and dominating bacteria, with a relatively low growth of E. coli O157:H7 in sliced smoked turkey during the shelf life under all storage regimes compared to the control. However, the pathogen survival was highest on the sliced smoked turkey under T1, decreasing by only 0.67, 0.74, 0.63, and 1.30 log CFU/g within 37 days if kept at 0, 5, 10, and 15 °C, respectively. Under T2 and the same condition, E. coli O157:H7 in the product declined by only 0.31, 0.50, 0.72, and 1.10 log CFU/g within 37 days of storage, respectively. In the T3 samples, the pathogen was reduced by only 0.33, 0.67, 1.72, and 3.46 log CFU/g through 37 days of storage, respectively. Under T3 were E. coli O157:H7 populations in smoked turkey eliminated (negative by enrichment) under all conditions (after 129, 95, 95, and 43 days maintained at 0, 5, 10, and 15 °C, respectively) compared with other packaging temperature combinations. Thus, T3 contributed to developing ready-to-eat smoked turkey with enhanced product quality and eliminating the pathogen.

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Growth Potential of Listeria monocytogenes on Refrigerated Spinach and Rocket Leaves in Modified Atmosphere Packaging

Foods ◽

10.3390/foods9091211 ◽

2020 ◽

Vol 9 (9) ◽

pp. 1211

Author(s):

Paul Culliney ◽

Achim Schmalenberger

Keyword(s):

Listeria Monocytogenes ◽

Modified Atmosphere Packaging ◽

Growth Curves ◽

High Growth ◽

Food Product ◽

Growth Potential ◽

Modified Atmosphere ◽

Visual Appearance ◽

Iceberg Lettuce ◽

Duration Of Storage

Minimally processed ready-to-eat (RTE) vegetables are increasingly consumed for their health benefits. However, they also pose a risk of being ingested with food-borne pathogens. The present study investigated the ability of RTE spinach and rocket to support the growth of Listeria monocytogenes as previous studies provided contradicting evidence. Findings were compared to growth on iceberg lettuce that has repeatedly been shown to support growth. Products were inoculated with a three-strain mix of L. monocytogenes at 10 and 100 cfu g−1 and stored in modified atmosphere (4 kPa O2, 8 kPa CO2) at 8 °C over 7–9 days. Spinach demonstrated the highest growth potential rate of 2 to 3 log10 cfu g−1 over a 9-day period with only marginal deterioration in its visual appearance. Growth potential on rocket was around 2 log10 cfu g−1 over 9 days with considerable deterioration in visual appearance. Growth potential of iceberg lettuce was similar to that of rocket over a 7-day period. Growth curves fitted closely to a linear growth model, indicating none to limited restrictions of growth over the duration of storage. The high growth potentials of L. monocytogenes on spinach alongside the limited visual deterioration highlight the potential risks of consuming this raw RTE food product when contaminated.

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Effect of Gamma Radiation and Oregano Essential Oil on Murein and ATP Concentration of Listeria monocytogenes

Journal of Food Protection ◽

10.4315/0362-028x-69.12.2961 ◽

2006 ◽

Vol 69 (12) ◽

pp. 2961-2969 ◽

Cited By ~ 19

Author(s):

STÉPHANE CAILLET ◽

MONIQUE LACROIX

Keyword(s):

Listeria Monocytogenes ◽

Essential Oil ◽

Gamma Radiation ◽

Cell Damage ◽

Electron Microscopic Observation ◽

Wall Structure ◽

Electron Microscopic ◽

Oregano Essential Oil ◽

Transmission Electron ◽

Oregano Oil

The effects of gamma radiation and of oregano essential oil alone or in combination with radiation on murein composition of Listeria monocytogenes and on the intracellular and extracellular concentration of ATP were evaluated. The bacterial strain was treated with two radiation doses, 1.2 kGy to induce cell damage and 3.5 kGy to cause cell death. Oregano essential oil was used at 0.020 and 0.025% (wt/vol), which is the MIC. All treatments had a significant effect (P ≤ 0.05) on the murein composition, although some muropeptides did not seem to be affected by the treatment. Each treatment influenced differently the relative percentage and number of muropeptides. There was a significant correlation (P ≤ 0.05) between the reduction of intracellular ATP and increase in extracellular ATP, following treatment of the cells with oregano oil. The reduction of intra-cellular ATP was even more important when essential oil was combined with irradiation, but irradiation of L. monocytogenes alone induced a significant decrease (P ≤ 0.05) of the internal ATP without affecting the external ATP. Transmission electron microscopic observation revealed that oregano oil and irradiation have an effect on cell wall structure.

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