Species Pervasiveness Within the Group of Coagulase-Negative Staphylococci Associated With Meat Fermentation Is Modulated by pH.

Despoina Angeliki Stavropoulou,Alberto Berardo,Luc De Vuyst,Stefaan De Smet,Panagiota Filippou,Bente Janssens,Hannelore De Maere,Frédéric Leroy

doi:10.3389/fmicb.2018.02232

Abstract

During spontaneous meat fermentations, Staphylococcus equorum, Staphylococcus saprophyticus, and Staphylococcus xylosus are generally the most prevailing species within the communities of coagulase-negative staphylococci (CNS). There is an interest to introduce CNS isolates from artisan-style spontaneous meat fermentations as starter cultures in more industrialized processes, as to confer additional quality benefits. However, staphylococcal competitiveness within the meat matrix is affected by the processing conditions, which vary considerably among product types. A major factor of variability relates to the intensity of acidification, driven by the concentration of added carbohydrates. The effect of pH on CNS prevalence was studied in both a mince-based meat fermentation model and in fermented sausages produced on pilot scale. Roughly, from all experiments combined, it appeared that a pH of 5.3 corresponded with a breakpoint for CNS selection. Above this value, a general prevalence by S. xylosus was found, even overruling the addition of starter cultures consisting of S. equorum and S. saprophyticus strains. At pH values below 5.3, S. xylosus was also accompanied by S. equorum (following a mild pH drop) and S. saprophyticus (following a stronger pH drop). Still, addition of starter cultures affected the volatile profile compared to the control batch, even if those starter cultures were not able to dominate during the ripening process. This study nonetheless provides a warning for an overly confident use of specific CNS species as starter cultures, especially when in a given processing context the prevailing conditions do not allow superior growth compared to the CNS from the background microbiota.

Highlights

Coagulase-negative staphylococci (CNS) are fundamental to the process of meat fermentation, whereby their metabolic activities contribute to the development of qualitative end-products (Sánchez Mainar et al, 2017)
The experiment using fermented mince-based meat models without added CNS indicated that S. xylosus became the leading CNS species during the first days of fermentation and was accompanied by either S. equorum in the mildly acidified batches and by S. saprophyticus in the most acid variants
Note that a minor fraction of S. carnosus emerged in the batches with the lowest pH, as this CNS species is known for its robustness toward acidic conditions but poor adaptation to higher pH values (Stavropoulou et al, 2018a)

Summary

Introduction

Coagulase-negative staphylococci (CNS) are fundamental to the process of meat fermentation, whereby their metabolic activities contribute to the development of qualitative end-products (Sánchez Mainar et al, 2017). CNS in Fermented Meats of selected lactic acid bacteria (LAB) and CNS strains to allow more control over the process (Leroy et al, 2006). The artisan-type technique of spontaneous fermentation is still in use, albeit rarely on an industrial scale (Talon et al, 2007; Coton et al, 2010; Janssens et al, 2013; Leroy et al, 2015). The acidification level is one of the main factors shaping the CNS microbiota during meat fermentation, whether they are added as starter cultures or not (Stavropoulou et al, 2018a,b). Common in many types of fermented sausages, affects the pH through the consumption of lactic acid and, modulates staphylococcal composition as well (Janssens et al, 2013)

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Conclusion