Effect of food structure and buffering capacity on pathogen survival during in vitro digestion

Even though a plethora of barriers are employed by the human gastrointestinal tract (GIT) to cope with invading pathogens, foodborne diseases are still a common problem. The survival of food pathogens in the GIT is known to depend on food carrier properties. The aim of this study was to investigate the influence of food buffering capacity and food structure on the survival of Salmonella Typhimurium and Listeria monocytogenes during simulated digestion, following contamination of different food model systems that had different combinations of fat and protein content. The results illustrated the strong protective properties of proteins, acting either as a strong buffering agent or as a physical barrier against gastric acidity, for both pathogens. In comparison, fat manifested a lower buffering capacity and weaker protective effects against the two pathogens. Intriguingly, a low fat content was often linked with increased microbial resistance. Nonetheless, both pathogens survived their transit through the simulated GIT in all cases, with S. Typhimurium exhibiting growth during intestinal digestion and L.monocytogenes demonstrating a healthy residual population at the end of the intestinal phase. These results corroborate the need for a deeper understanding regarding the mechanisms with which food affects bacterial survival in the human GIT.