Abstract
The aim of this study was to obtain the growth parameters of specific spoilage micro-organisms previously isolated in minced pork (MP) samples and to develop a three-spoilage species interaction model under different storage conditions. Naturally contaminated samples were used to validate this approach by considering the effect of the food microbiota. Three groups of bacteria were inoculated on irradiated samples, in mono- and in co-culture experiments (n = 1152): Brochothrix thermosphacta, Leuconostoc gelidum, and Pseudomonas spp. (Pseudomonas fluorescens and Pseudomonas fragi). Samples were stored in two food packaging [food wrap and modified atmosphere packaging (CO2 30%/O2 70%)] at three isothermal conditions (4, 8, and 12°C). Analysis was carried out by using both 16S rRNA gene amplicon sequencing and classical microbiology in order to estimate bacterial counts during the storage period. Growth parameters were obtained by fitting primary (Baranyi) and secondary (square root) models. The food packaging shows the highest impact on bacterial growth rates, which in turn have the strongest influence on the shelf life of food products. Based on these results, a three-spoilage species interaction model was developed by using the modified Jameson-effect model and the Lotka Volterra (prey–predator) model. The modified Jameson-effect model showed slightly better performances, with 40–86% out of the observed counts falling into the Acceptable Simulation Zone (ASZ). It only concerns 14–48% for the prey–predator approach. These results can be explained by the fact that the dynamics of experimental and validation datasets seems to follow a Jameson behavior. On the other hand, the Lotka Volterra model is based on complex interaction factors, which are included in highly variable intervals. More datasets are probably needed to obtained reliable factors, and so better model fittings, especially for three- or more-spoilage species interaction models. Further studies are also needed to better understand the interaction of spoilage bacteria between them and in the presence of natural microbiota.
Highlights
During production and distribution steps, spoilage of meat and meat products may occur, rendering them unacceptable for human food consumption
It is well known that the initial bacterial counts on meat and meat products is highly variable (Benson et al, 2014), but several studies have established that only a dominant fraction of the microbiota, designated as specific spoilage organisms (SSOs), contributes to spoilage (Nychas et al, 2008; Kreyenschmidt et al, 2010; Pennacchia et al, 2011; Benson et al, 2014; Zotta et al, 2019)
This study considers the effect of two bacteria, Pseudomonas fluorescens and Listeria innocua, on the bacterial growth of Listeria monocytogenes
Summary
During production and distribution steps, spoilage of meat and meat products may occur, rendering them unacceptable for human food consumption. It is well known that the initial bacterial counts on meat and meat products is highly variable (Benson et al, 2014), but several studies have established that only a dominant fraction of the microbiota, designated as specific spoilage organisms (SSOs), contributes to spoilage (Nychas et al, 2008; Kreyenschmidt et al, 2010; Pennacchia et al, 2011; Benson et al, 2014; Zotta et al, 2019) In this context, predictive microbiology can be a helpful tool because the prediction of microbial growth, especially SSOs, enables food industries to optimize their production and storage managements, and reduce their economic losses (Kreyenschmidt et al, 2010; Fakruddin et al, 2012; Li et al, 2017; Tamplin, 2018). These models often describe the growth of the SSOs depending on the storage temperature (Dominguez and Schaffner, 2007; Gospavic et al, 2008; Kreyenschmidt et al, 2010; Psomas et al, 2011; Longhi et al, 2013; Antunes-Rohling et al, 2019) or the packaging conditions (Devlieghere et al, 1999; Chaix et al, 2015; Guillard et al, 2016; Couvert et al, 2019; Kapetanakou et al, 2019), but do not always consider the interaction of these storage conditions for the growth of spoilage bacteria (Rosso et al, 1995; Augustin and Carlier, 2000; Le Marc et al, 2002; Pinon et al, 2004; Dalcanton et al, 2018; Kakagianni et al, 2018; Nyhan et al, 2018; Correia Peres Costa et al, 2019)
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