title: Identification of H₂O₂ as a major antimicrobial component in coffee.
abstract: Coffee shows distinct antimicrobial activity against several bacterial genera. The present study investigated molecular mechanisms and active ingredients mediating the antimicrobial effect of coffee. Depending on concentration, roasted, but not raw coffee brew inhibited the growth of Escherichia coli and Listeria innocua. Several coffee ingredients with known antibacterial properties were tested for their contribution to the observed effect. In natural concentration, caffeine, ferulic acid and a mixture of all test compounds showed very weak, but significant activity, whereas trigonelline, 5-(hydroxymethyl)furfural, chlorogenic acid, nicotinic acid, caffeic acid, and methylglyoxal were not active. Antimicrobial activity, however, was completely abolished by addition of catalase indicating that H(2)O(2) is a major antimicrobial coffee component. In accordance with this assumption, bacterial counts during 16 h of incubation were inversely related to the H(2)O(2) concentration in the incubation solution. Pure H(2)O(2) showed slightly weaker activity. The H(2)O(2) dependent antimicrobial activity of coffee could be mimicked by a reaction mixture of d-ribose and l-lysine (30 min 120 °C) indicating that H(2)O(2) is generated in the coffee brew by Maillard reaction products. Identification of H(2)O(2) as major antimicrobial coffee component is important to evaluate the application of coffee or coffee extracts as natural preservatives.
authors.affiliation: Department of Chemistry and Pharmacy, Food Chemistry, Emil Fischer Center, Friedrich-Alexander University Erlangen-Nuremberg.
authors.forename: Ulla
authors.initials: U
authors.lastname: Mueller
authors.forename: Tanja
authors.initials: T
authors.lastname: Sauer
authors.forename: Ingrid
authors.initials: I
authors.lastname: Weigel
authors.forename: Rohtraud
authors.initials: R
authors.lastname: Pichner
authors.forename: Monika
authors.initials: M
authors.lastname: Pischetsrieder
mesh_terms: D000470:Alkaloids / Q000032:analysis; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002110:Caffeine / Q000032:analysis; D002726:Chlorogenic Acid / Q000032:analysis; D003069:Coffee / Q000737:chemistry*; D003373:Coumaric Acids / Q000032:analysis; D003470:Culture Media / Q000032:analysis; D004926:Escherichia coli / Q000187:drug effects; D005662:Furaldehyde / Q000031:analogs & derivatives / Q000032:analysis; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008087:Listeria / Q000187:drug effects; D008239:Lysine / Q000378:metabolism; D010936:Plant Extracts / Q000494:pharmacology*; D012266:Ribose / Q000378:metabolism; D013696:Temperature
chemical_list: D000470:Alkaloids; D000890:Anti-Infective Agents; D003069:Coffee; D003373:Coumaric Acids; D003470:Culture Media; D010936:Plant Extracts; D002726:Chlorogenic Acid; D002110:Caffeine; C009560:trigonelline; D012266:Ribose; C008046:5-hydroxymethylfurfural; C004999:ferulic acid; D006861:Hydrogen Peroxide; D005662:Furaldehyde; D008239:Lysine