Modelling the growth rate ofListeria monocytogenesin cooked ham stored at different temperatures

Abstract

Introduction: The purpose of the study was to determine and model the growth rates of L. monocytogenes in cooked cured ham stored at various temperatures. Material and Methods: Samples of cured ham were artificially contaminated with a mixture of three L. monocytogenes strains and stored at 3, 6, 9, 12, or 15ºC for 16 days. The number of listeriae was determined after 0, 1, 2, 3, 5, 7, 9, 12, 14, and 16 days. A series of decimal dilutions were prepared from each sample and plated onto ALOA agar, after which the plates were incubated at 37ºC for 48 h under aerobic conditions. The bacterial counts were logarithmised and analysed statistically. Five repetitions of the experiment were performed. Results: Both storage temperature and time were found to significantly influence the growth rate of listeriae (P < 0.01). The test bacteria growth curves were fitted to three primary models: the Gompertz, Baranyi, and logistic. The mean square error (MSE) and Akaike's information criterion (AIC) were calculated to evaluate the goodness of fit. It transpired that the logistic model fit the experimental data best. The natural logarithms of L. monocytogenes' mean growth rates from this model were fitted to two secondary models: the square root and polynomial. Conclusion: Modelling in both secondary types can predict the growth rates of L. monocytogenes in cooked cured ham stored at each studied temperature, but mathematical validation showed the polynomial model to be more accurate.

Listeria monocytogenes Biofilm Adaptation to Different Temperatures Seen Through Shotgun Proteomics

“…The cleaning and disinfection of surfaces and materials in food industries is difficult to achieve due to L. monocytogenes capacity to survive under harsh condition, such as a wide pH range (79), desiccated environments (9, 20), and low temperatures (80). Since L. monocytogenes is a psychrotrophic microorganism able to multiply in food stored under refrigerated temperatures, a low contamination number present in RTE products can grow to a level which threatens consumer health (81). At low temperatures, Listeria faces multiple molecular constraints such as increased membrane rigidity, amino acid starvation, oxidative stress, aberrant protein synthesis, cell surface remodeling, reduced protein and enzyme activity, slow transport, and nutrient uptake processes (56, 82).…”

Listeria monocytogenes Survey in Cubed Cooked Ham Packaged in Modified Atmosphere and Bioprotective Effect of Selected Lactic Acid Bacteria

“…Listeria monocytogenes can cause fatal disease (30–40%) in foetuses, infants, pregnant women, elderly subjects and immunocompromised individuals with cancer, kidney disease, heart disease or AIDS; subject to organ transplants; and/or treated with immunosuppressants [ 1 , 2 , 3 ]. The incidence of the disease caused by L. monocytogenes , which is named listeriosis, is decreasing and varies every year.…”

Estimating Listeria monocytogenes Growth in Ready‐to‐Eat Chicken Salad Using a Challenge Test for Quantitative Microbial Risk Assessment

“…Refrigeration is one of the most common procedures used in food processing and distribution to ensure food safety during product's shelf‐life (Melo, Andrew, & Faleiro, 2015). However, the ability of L. monocytogenes to grow in refrigerated foods may potentially threaten consumer's health (Szczawiński, Szczawińska, Łobacz, Tracz, & Jackowska‐Tracz, 2017). Because of that, European legislation establishes a limit of 100 colony‐forming units per gram of food at the end of shelf‐life, whether the food is able or not to support the growth of L. monocytogenes (European Commission, 2005).…”

“…Therefore, accurate information on the behavior of L. monocytogenes in RTE salads constitutes crucial knowledge. Experimental data regarding L. monocytogenes ’ growth obtained during storage at different temperatures can be described mathematically by predictive models that can be used in subsequent quantitative microbial risk assessments (QMRAs) (Szczawiński et al., 2017). QMRA is often used to evaluate risk in food safety, as it offers a logical and structured approach to assess risks due to the consumption of a hazard in a specific food.…”