Metabolites produced during the growth of probiotics in cocoa supplementation and the limited role of cocoa in host-enteric bacterial pathogen interactions

Cocoa contains various compounds that can significantly affect the growth of a broad range of bacteria, and have multiple human health-promoting properties. In this study, the effects of cocoa powder on the growth of Lactobacillus, common milk resident bacteria, and three major foodborne enteric bacterial pathogens; enterohemorrhagic Escherichia coli O157:H7 (EHEC), Salmonella enterica serovar Typhimurium, and Listeria monocytogenes, were investigated in vitro. Significant (p < 0.05) growth stimulation on beneficial bacteria including Lactobacillus and other resident bacteria in milk was observed in the presence of 3% cocoa powder. In contrast, growth of three foodborne enteric pathogens was significantly (p < 0.05) inhibited within 9 h, but no stimulation was found with longer incubation. In addition, cocoa powder significantly (p < 0.05) inhibited adhesion to and invasion of INT407 cells by these bacterial pathogens in a dose dependent manner. These results suggest that addition of cocoa into dairy products could improve the beneficial effect of probiotics by stimulating their growth, without raising the risk of cross-contamination with enteric pathogens.