Suspicion over chemical-derived synthetic preservatives has pushed food makers to source natural preservatives such as rosemary extract instead, and market analysts Global Information pitch the global food preservative market at €422.7bn, reaching €522bn by 2008.
"It may be concluded that, the ethanolic extract of propolis tested, in the performed experimental conditions may successfully inhibit the E. coli development in vitro, at safe levels for human consumption and, consequently, they could be useful as ground fresh beef natural preserver or as unspecific antibacterial food preserver," wrote lead author Enzo Tosi in the journal Food Chemistry.
Tosi and his co-workers from Argentina's National University if Technology looked at the effect of Argentinian propolis extracts against E.coli, and thereby as a preservative for foods.
"Most propolis components are natural constituents of food and recognized as safe substances," added Tosi.
The researchers report that an average minimum inhibitory concentration of 14.3 mg soluble compounds per millilitre of the most active propolis was capable of inhibiting E. coli populations of up to 10,000 cells per millilitre.
Such an extract was said to be composed of 32 per cent total soluble compounds, comprising eight per cent galangine, seven per cent caffeic acid, five per cent quercitin, two per cent coumaric, and nine per cent no-identified phenolics compounds.
"From the consumer standpoint, a safe dose for human consumption would be 1.4 mg/kg body weight/day, or approximately 70 mg/day in adults," said the researchers. "Suitable levels of propolis as food preserver must be established by a consumer acceptance test by a trained tasting panel."
Further research is clearly necessary, and variations over local and botanical factors may limit the applicability and sustainability of this novel preservative.
"The propolis extracts tested, may successfully inhibit the E. coli development in vitro, and consequently may be useful as natural food preserver," concluded the researchers.
It is reported that propolis contains about 180 different compounds and the waxy resin has previously been linked to improvements of general health, skin health, and oral health.
Source: Food Chemistry (Elsevier)
Published on-line ahead of print, doi: 10.1016/j.foodchem.2007.01.011
"Food preservative based on propolis: Bacteriostatic activity of propolis polyphenols and flavonoids upon Escherichia coli"
Authors: E.A. Tosi, E. Ré, M.E. Ortega and A.F. Cazzoli