Antibacterial Properties

Honey exhibits antibacterial properties - the growth of bacteria is inhibited due to the low water activity, high acidity, and the hydrogen peroxide activity (PA). This activity has been reviewed extensively by Molan (1992), and is usually measured by diffusion assays (Patton et al, 2006). In this technique, sample material is placed into wells bored into inoculated agar growth media, this diffuses into the agar around the well, and produces a zone of inhibited bacterial growth. Inhibition zones are used to determine the potency of the sample tested. Alternatively, discs prepared from sterile absorbent material are soaked in the sample solution and placed on inoculated growth media. The samples diffuse into the agar around the disc and are assayed for the ability to produce a zone of inhibition also. Patton et al (2006) developed another method, a spectrophotometric assay, with greater sensitivity to also assess antibacterial activity in honey.

Hydrogen peroxide is the principal component responsible for the antibacterial action of honey, although phenolic acids, lysozyme and flavonoids also contribute to a lesser degree (Weston et al, 1999; 2000). Hydrogen peroxide is synthesised through the oxidation of glucose, a reaction is catalysed by the enzyme glucose oxidase. This enzyme originates from the hypopharyngeal glands of the bee (White, 1978), and as with many enzymes, it is inactivated by light and heat. The more intense the level of light or heat, the faster the rate of inactivation. Room temperature and/or light, given enough time, is sufficient to reduce glucose oxidase activity, meaning that antibacterial activity in honeys can vary.

Hydrogen peroxide content has been shown to vary between honeys of different floral sources also:

Recent Research on Hydrogen Peroxide in NZ monofloral honeys

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