Tea and soybean extracts in combination with milk fermentation inhibit growth and enterocyte adherence of selected foodborne pathogens

• Extracts of tea and soybean showed dose-dependent growth inhibition of pathogens.
• Growth of pathogens and their adhesion to Caco-2 cells were inhibited by extracts.
• Phenolic-enriched milk (PEM) was formulated, fermented with LAB and ultrafiltered.
• Fermented PEM inhibited bacterial growth and enterocyte adhesion more significantly.
• Multiple agents may exhibit synergistic antibacterial and anti-adhesive activity.

This study examined the antibacterial and anti-adhesive properties of pure plant extracts (PPEs) of green tea (GT), black tea (BT) and soybean individually or in combination with milk. Fermented phenolic enriched-milk (fPEM) was prepared by combining PPEs with milk and fermented with lactic acid bacteria. Antimicrobial activity of extracts was evaluated by broth-dilution and agar diffusion assay. Anti-adhesive property of extracts was evaluated in Caco-2 cell model. Results from antibacterial tests showed that PPEs exhibited a dose-dependent growth inhibitory effect. Tea extracts were more effective in inhibiting Gram-positive bacteria while soybean extract exhibited similar effects against all pathogens tested. For fPEM, although total phenolic contents decreased compared with those in PPEs, growth inhibitory effect of fPEM containing tea extracts was greatly enhanced. All extracts showed significant inhibition against pathogen adhesion to Caco-2 cells. In particular, adhesion inhibition against Staphylococcus aureus and Listeria monocytogenes was >89% when fPEM extracts were applied.