Inhibitory activity of honey against foodborne pathogens as influenced by the presence of hydrogen peroxide and level of antioxidant power

Antimicrobial activity of honey has been attributed to hydrogen peroxide, w hich is produced by naturally occurring glucose oxidase, and phenolic compo unds, although lethality of and inhibition by these and other components ag ainst microorganisms vary greatly, depending on the floral source of nectar . This study was undertaken to compare honeys from six floral sources for t heir inhibitory activity against Escherichia coli O157:H7, Salmonella typhi murium, Shigella sonnei, Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus. A disc assay revealed that development of zones of inhibi tion of growth depends on the type and concentration of honey, as well as t he test pathogen. Growth of B. cereus was least affected. The inhibition of growth of S. sonnei, L. monocytogenes, and S. aureus in 25% solutions of h oneys was reduced by treating solutions with catalase, indicating that hydr ogen peroxide contributes to antimicrobial activity. Darker colored honeys were generally more inhibitory than light colored honeys. Darker honeys als o contained higher antioxidant power. Since antimicrobial activity of the d arker colored test honeys was not eliminated by catalase treatment, non-per oxide components such as antioxidants. may contribute to controlling the gr owth of some foodborne pathogens. The antibacterial properties of honeys co ntaining hydrogen peroxide and characterized by a range of antioxidant powe r need to be validated using model food systems. (C) 2001 Elsevier Science B.V. All rights reserved.