Modelling the kinetics of Listeria monocytogenes in refrigerated fresh beef under different packaging atmospheres

Abstract

a b s t r a c tThe objective of this study was to model the fate of Listeria monocytogenes inoculated in beef at two concentrations (2.5 and 4.0 log CFU/g), packaged under air, vacuum and three modified atmospheres MAP: 70%O 2 /20%CO 2 /10%N 2 , 50%O 2 /40%CO 2 /10%N 2 and 30%O 2 /60%CO 2 /10%N 2 , and refrigerated at a normal temperature (4 C) and at a mild abusive temperature (9 C). The experimental design produced a total of 20 environmental conditions. An omnibus model based on the Weibull equation proved statistically that L. monocytogenes survives better in vacuum (VP) than in aerobic conditions, although without significant difference in its ability to survive in the temperature range between 4 C and 9 C. Furthermore, regardless of the refrigeration temperature, the presence of CO 2 in the package atmosphere exerted a bactericidal effect on L. monocytogenes cells, being approximately 1.5 log of reduction when storage time reached 10 days. Since the pathogen can survive in VP/MAP beef, there is a need of maintaining its numbers below 100 CFU/g before packaging by placing efforts on the implementation of control measures during processing.

Modeling the Behavior of Listeria monocytogenes in Meat

“…monocytogenes growth in vacuum-packaged beef stored at 0 and 5 C. They indicated that growth of this bacteria on beef depends on the storage temperature, pH and the type of tissue (fat or lean). Although L. monocytogenes grows at both temperatures, a scarce lag period was observed in beef stored at 5 C. Similarly, [35] observed an increase of lag phase of L. monocytogenes in beef samples stored at 4 C compared to those stored at 9 C. In a study with pork cuts [38] stored at mean refrigerator temperatures did not increase the populations of L. monocytogenes over 2 log CFU/g in the end of product shelf-life. However, at abusive temperatures, microbial counts were higher than 3 log CFU/g for some cases, which required a more severe heat inactivation treatment before consumption.…”

“…Although regarding vacuum packaging, this preservation methodology seems not affecting the growth of L. monocytogenes as observed by [16]. With reference to [35], it was showed that L. monocytogenes survives better in vacuum packaging than in air-packed beef samples. According to [36], neither L. monocytogenes grow after 42 days of storage nor significant reductions were observed in inoculated vacuum-packed beef stored at 4 C[37]obse rv edL.…”

“…The growth of L. monocytogenes is scarcely affected by anaerobic or oxygen-reduced atmosphere. According to [16,35], modified atmosphere packaging (MAP) systems may reduce the survival and growth of L. monocytogenes by the presence of carbon dioxide in modified atmosphere packaging (MAP). In fresh beef, MAP with 60% CO 2 : 30% O 2 : 10% N 2 prevented growth at 4 C for more than 2 weeks of storage.…”

“…According to [61], the role of microbial competition in models is now taken into consideration. Some studies were published regarding the survival of L. monocytogenes in fresh beef stored at two temperatures and different packaging systems as modified atmosphere packaging (MAP), using omnibus model based on the Weibull Equation [35]. Besides the increase of studies using predictive models, there are few data referred to the application of predictive models to composite foods containing raw and cooked ingredients [67].…”

Assessment of Spoilage Bacterial Communities in Food Wrap and Modified Atmospheres-Packed Minced Pork Meat Samples by 16S rDNA Metagenetic Analysis

“…The composition of modified atmosphere systems can be an effective way to reduce the growth rate of spoilage aerobic organisms and modify the microbial ecology of the product. But their effectiveness strongly depends on the initial microbial contamination of raw materials, storage temperature, film permeability and the carbon dioxide concentration used (20-40% is commonly used to suppress microbial growth) (Simpson and Carevic, 2004;Rotabakk et al, 2006;Stoops et al, 2015;Guillard et al, 2016;Saraiva et al, 2016;Couvert et al, 2017). The carbon dioxide concentration was here theoretically sufficient to limit the microbial growth.…”