Compatibility of Commercially Produced Protective Cultures with Common Cheesemaking Cultures and Their Antagonistic Effect on Foodborne Pathogens

Abstract

The documented survival of pathogenic bacteria, including Listeria monocytogenes (LM), Shiga toxin–producing Escherichia coli (STEC), and Salmonella during the manufacture and aging of some cheeses highlights the need for additional interventions to enhance food safety. Unfortunately, few interventions are compliant with the Standards of Identity for cheese. Protective bacterial cultures (PCs) represent actionable, natural interventions. However, supportive data for commercially produced PCs regarding their efficacy against pathogens and potential antagonism with each other and cheesemaking cultures are scant, thereby impeding their potential use by the cheese industry. The overall objective of this study was to identify commercially produced PCs that exert antimicrobial activity toward pathogens with minimal impact on beneficial cheese microbes. Direct antagonism and agar well diffusion assays were used to determine the impact of 10 commercially produced PCs on the growth of starter cultures and cultures of ripening bacteria and fungi. Deferred antagonism was used to evaluate the potential for antimicrobial effects against LM, STEC, and Salmonella. PCs and starter cultures were cocultured in ultrahigh-temperature-processed milk to determine the effects of coculture on starter acidification profiles when incubated according to a simulated cheesemaking temperature profile (4 h at 35°C followed by 20 h at 20°C). Compatibility assays suggest that PC antagonism is microbe and strain specific. Only one PC negatively impacted the acidification of the starters tested. PC antagonism of ripening bacteria and fungi growth varied but was consistent within species. All PCs displayed deferred inhibition of LM, STEC, and Salmonella growth, but to varying degrees. These data identify commercial PCs with potential for the control of pathogens and characterize their compatibility with cheesemaking cultures for future use by cheesemakers and investigations of their efficacy in the production of cheese. HIGHLIGHTS

Effect of storage temperature and produce type on the survival or growth of Listeria monocytogenes on peeled rinds and fresh-cut produce

“…L. monocytogenes levels remained the same in these fruit samples stored at 4°C, possibly influenced by competition for nutrients with yeasts and molds. Gramisci et al (2018) and Gensler et al (2020) both demonstrated the antagonistic effect that the growth of yeast and mold can have on foodborne pathogens.…”

Lactic Acid Bacteria Adjunct Cultures Exert a Mitigation Effect against Spoilage Microbiota in Fresh Cheese

“…When the three adjunct cultures were evaluated as a pool, positive results were obtained at 8 and 14 °C mostly due to the presence of Carnobacterium , but also to the synergic effect generated by bacteriocins production by the three bacterial strains. LAB mixed cultures often demonstrated to exert a highest protective action without affecting the cheese making and the final organoleptic properties [ 14 , 15 , 56 ]. As a general observation, the use of adjunct cultures significantly shapes the cheese microbiota, by reducing the alpha-diversity index, as shown in Figure 4 .…”

A Snapshot, Using a Multi-Omic Approach, of the Metabolic Cross-Talk and the Dynamics of the Resident Microbiota in Ripening Cheese Inoculated with Listeria innocua

“…On the other hand, the metabolic behavior of Lactobacillus spp. in one cheese has been investigated by means of traditional analytical techniques [ 14 ], but no detailed description of the released compounds has been reported while interacting with pathogens [ 16 , 17 , 20 , 22 , 23 , 24 , 25 , 26 ]. Recently, Tzora et al [ 27 ] established differences in the molecular signaling (also called cross-talk) exchanged between resident microbiota in Kefalograviera cheese after the feeding system of the dairy sheep was changed.…”