Antibacterial effect of water-soluble tea extracts on foodborne pathogens in laboratory medium and in a food model.
The microbial inhibition of foodborne pathogens was determined in brain heart infusion broth with 10% (wt/vol) water-soluble extracts of green, jasmine, black, dungglre, and oolong tea against Escherichia coli O157:H7, Salmonella enterica serovar Enteritidis, Listeria monocytogenes, and Staphylococcus aureus. The mixed culture (approximately 6.0 log CFU/ml), which was composed of the four pathogens, was inoculated into brain heart infusion broth with and without tea extracts. After incubation at 35 degrees C for 0, 1, 3, and 5 days, proper dilution of each sample was spiral plated on each selective agar. Viable cell counts were performed after incubation at 35 degrees C for 24 to 36 h. Green, jasmine, and black tea exhibited an approximately 5.0 log suppression of S. aureus compared with the control from days 1 to 5. Green and jasmine tea also suppressed the growth of L. monocytogenes by approximately 3.0 log CFU/ml on day 5. In contrast, no tea extracts inactivated E. coli O157:H7 and Salmonella Enteritidis. Based on the result in liquid medium, green and jasmine teas of 0.1% (vol/wt) were individually evaluated for their antimicrobial activity against L. monocytogenes and S. aureus in a food model (ground beef) stored at 7 degrees C for 0, 1, 3, 5, and 7 days. Viable cell counts of total bacteria, L. monocytogenes, and S. aureus in ground beef were not significantly different among green and jasmine tea and the control.
Kim
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Food Microbiology Laboratory, Department of Animal Sciences and Industry, Kansas State University, Manhattan, Kansas 66506-1600, USA. kim98@purdue.edu
Ruengwilysup
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Fung
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D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development; D015169:Colony Count, Microbial; D003470:Culture Media / Q000737:chemistry; D019453:Escherichia coli O157 / Q000187:drug effects / Q000254:growth & development; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods; D008089:Listeria monocytogenes / Q000187:drug effects / Q000254:growth & development; D010936:Plant Extracts / Q000494:pharmacology*; D012477:Salmonella enteritidis / Q000187:drug effects / Q000254:growth & development; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development; D013662:Tea / Q000737:chemistry*; D013997:Time Factors
D000900:Anti-Bacterial Agents; D003470:Culture Media; D010936:Plant Extracts; D013662:Tea