Saturday, October 24, 2009

Antimicrobial Activity of Honey

Antimicrobial Activity of Honey Against Food Pathogens and Food Spoilage Microorganisms
M. A. MUNDO1, O. I. Padilla-Zakour, and R. W. Worobo. (1)
Department of Food Science and Technology, Cornell University, NYSAES, W North St, Geneva, NY 14456

The growth of many microorganisms is either partially or completely inhibited in the presence of diluted honey. Previous researchers have demonstrated strong antibacterial activity by specific honey samples against Staphylococcus aureus. We are interested in detecting the spectrum of antimicrobial activity against several food pathogens and spoilage microorganisms. Our research objective was to investigate the antimicrobial activity of different types of honey against food pathogens and food spoilage microorganisms.

A variety of American honey samples were tested for antimicrobial activity by placing 0.2 g of honey into well diffusion agar plates, with 1.0% of the test microorganism inoculated into a 0.75% overlay agar. Six pathogenic and six spoilage microorganisms were evaluated. Inhibition zones were analyzed for both full-strength and diluted honey. Physical and chemical evaluations of each honey were also performed, including pH, Titratable Acidity, soluble solids (Brix), total phenols (Folin-Ciocalteu method), and color measurements.

The microorganisms tested were inhibited by both hydrogen peroxide and other antimicrobial agents found in the honey. A variety of antimicrobial activity exists within the floral source of the honeys. Tarweed and Montana Buckwheat samples impeded growth of Listeria monocytogenes at one-quarter and one-eighth dilutions, respectively, as well as Lactobacillus, Bacillus, E. coli and Salmonella at stronger dilutions. However, the Chinese Buckwheat sample was effective against E. coli and Salmonella only at full-strength. Gram negative bacteria seem to be inhibited by honey's high sugar concentration while Gram positive bacteria appear to require a threshold inhibitory level of antibacterial activity in order to prevent growth.

Certain varieties of honey were shown to exhibit non-peroxide antimicrobial activity and were capable of inhibiting the growth of food pathogens and food spoilage microorganisms. The incorporation of honey into foods could enhance their safety and shelf-life without the use of chemical preservatives.