An investigation of current and novel controls of the broiler meat-associated microbiota

Chicken meat is a product for which demand is growing due to its low cost, versatility and high nutritional value. However, it is also subject to microbial spoilage and pathogen contamination. There is a need to improve safety, with up to 90% of chicken meat contaminated with Salmonella or Campylobacter and concerns over increasing population vulnerability. These risks increase due to the prevalence of in-home cross-contamination events and poor preparation practices. The consistent adulteration of poultry meat products despite current interventions necessitates the development of new antimicrobial interventions prior to, during, and after product packaging, though the consequences of these interventions should be understood to maximise product safety while keeping public support. This thesis aimed to survey the current issue of poultry meat contamination, then propose realistic high impact and minimal consequence controls. • This thesis first sought to survey the microbiome of poultry meat and examine the effect that primary production factors have on its microbial integrity. To accomplish this, a comparative survey of the microbiota of conventionally produced and free-range chicken thighs from three processing facilities was conducted. • To assess secondary processing effects, two broiler processors were surveyed to assess the microbiome of the environment in which meat is processed, with particular attention to key critical control points prior to and after the chilling step of meat production. • To address consumer worries about antimicrobial interventions, antibacterial marinades were created utilising natural ingredients to control bacterial proliferation on chicken meat. • Given concerns about the development of antimicrobial resistance, virulence and bacterial stress responses, this thesis finally incorporated an assessment of the transcriptomic response of Salmonella or Campylobacter to antimicrobial stresses, including ultraviolet light, plasma functionalised water (PFW) and antimicrobial marinades. Comparing the microbiota of meat raised under conventional versus free-range systems found no significant difference in bacterial carriage in the end-product. This highlights that the processing environment, shared by both conventionally reared and free-range meat products in this study, had a greater overall effect on the microbiota composition. The poultry processor survey underlined the role that it plays in the establishment of an adaptable spoilage microbiome on broiler carcasses, as well as the role that the processor microbiome can play in product contamination. However, these results also emphasised the role that carcass carriage plays in Campylobacter perseverance, as it was not frequently found in processor sites. Antimicrobial marinading showed the desired effect in extending meat shelf-life while reducing the carriage of Salmonella enterica ser. Typhimurium, Campylobacter jejuni or Listeria innocua. However, recipe optimisation with a view to improving sensory characteristics to maintain consumer engagement is needed. This treatment offers an achievable means for consumers to engage in product safety while assuaging concerns about ‘natural’ vs ‘unnatural’ treatments. Transcriptomic analysis of sub-lethally UV/PFW/marinade-treated Salmonella and Campylobacter showed increases in cell activity, gene diversity and pathway expression. This was particularly in response to the antimicrobial marinade composition and spark cold plasma treated PFW, showing the high stress that these interventions cause microbes. The findings of this thesis both underline the need for improvements in antimicrobial interventions in current meat production practices, as well as support the implementation of optimised novel interventions in-line, in-package, and in-home. With the implementation of these technologies, safer food systems are possible, with benefits for consumers, producers, and society as a whole.