Aims : To find the minimum inhibitory concentration (MIC) in an in vitro assay of the antioxidants ascorbic acid, naringenin and quercetin against the foodborne pathogens Escherichia coli serotype 0157:H7 and Staphylococcus aureus and the opportunistic pathogen Pseudomonas aeruginosa. Results: Inhibition zones were recorded using a broad range of concentrations from 10,000 to 1 micrograms/ml on Escherichia coli serotype 0157:H7, Staphylococcus aureus and Pseudomonas aeruginosa. The MIC for the antioxidants ascorbic acid and naringenin were 1 micrograms/ml for P. aeruginosa and E. coli serotype 0157:H7, respectively. The MIC for quercetin was 1 micrograms/ml on E. coli serotype 0157:H7 while high concentrations of the antioxidant were required to inhibit S. aureus (MIC of 5,000 micrograms/ml) and P. aeruginosa (MIC of 7,500 micrograms/ml). Conclusions: Low concentrations (1 microgram/ml) of the antioxidants ascorbic acid and naringenin were effective on some of the evaluated bacteria (P. aeruginosa and E. coli serotype 0157:H7, respectively) and therefore could be incorporated into foods. The antioxidant quercetin was effective against the pathogenic bacteria Escherichia coli serotype 0157:H7 at low concentration (1 microgram/ml) while inhibition against S. aureus and P. aeruginosa required concentrations that if used as food additives would have a negative effect on the organoleptic properties of the foods. The assessment of the effective antioxidant concentration to eliminate these bacteria can be useful in developing value-added and safe food products.


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