Pervasiveness of Staphylococcus carnosus over Staphylococcus xylosus is affected by the level of acidification within a conventional meat starter culture set-up

Staphylococcus carnosus and Staphylococcus xylosus are commonly used, individually or in combination, within conventional starter cultures for the purposes of colour and flavour development during meat fermentation. Yet, little is known about the relative importance of both species under different processing conditions. The present study aimed at investigating the competitiveness of S. carnosus within a meat starter culture under different acidification profiles. The experimental set-up involved a gradient of decreasing experimental control but increasing realism, ranging from liquid meat fermentation models in a meat simulation medium, over solid mince-based meat fermentation models, to fermented sausage production on pilot-scale level. In general, S. carnosus gained a fitness advantage over S. xylosus in the most acidified variants of each set-up. In contrast, increasing persistence of S. xylosus was seen at the mildest acidification profiles, especially when approximating actual meat fermentation practices. Under such conditions, S. carnosus was reduced to co-prevalence in the mince-based meat fermentation models and was fully outcompeted on pilot-scale level. The latter was even the case when no S. xylosus starter culture was added, whereby S. carnosus was overpowered by staphylococci that originated from the meat background (mostly S. xylosus strains). The results of the present study suggested that conventional starter cultures behave differently when applied in different technological set-ups or using different recipes, with possible repercussions on fermented meat product quality.