GROWTH PARAMETER AND VIABILITY MODIFICATIONS OF Escherichia coli BY PHENOLIC COMPOUNDS

RODRIGUEZ VAQUERO M. J; MANCA DE NADRA M.C.

Trivandrum, India

Conferencia; International Conference on New Horizons in Biotechnology; 2007

Food contamination is an enormous public health problem. The actual tendency is the use of natural preservatives. Phenolic compounds are plant secondary metabolites abundant in foods and beverages. We investigated the anti-bacterial effect of pure non-flavonoids gallic, vanillic, protocatechuic and caffeic acids and pure flavonoids quercetin, rutin and catechin and the effect of  total polyphenols of three Argentinean wines varieties, Cabernet Sauvignon, Malbec and Merlot, against Escherichia coli, microorganism widely distributed in the environment and frequently detected in fresh and processed foods. Phenolic compounds were added to the medium at concentrations from 25 to 500 mg/l. Bacterial growth was determinate by measuring absorbance and by enumerating the number of viable cells. The clarified wines were used as control. The polyphenols effect was ethanol independent. In any case was observed cellular lysis. As the polyphenols concentrations in Merlot wine was higher than in Malbec wine, and Merlot and Malbec wines produced the cellular death at the same time, it is possibly to infer that the polyphenolic composition of Malbec wine was more effective to inhibit the viability of E. coli. So, we confirm that phenolic compounds of wines could be considered as antibacterial agents to prevent food contamination by this bacterium. The hydroxycinnamic derivate caffeic acid and the flavonoid quercetin were the more effectives against E. coli ATCC 35218. The comparative results of the polyphenols effect with those obtained previously with Listeria monocytogenes permit to conclude  that the effect of these biopreservatives are independent of the Gram-positive or Gram-negative microorganism character.