ANTIMICROBIAL EFFECTS OF MENTHA PULEGIUM ESSENTIAL OIL AND NISIN AGAINST STAPHYLOCOCCUS AUREUS IN COMMERCIAL BARLEY SOUP

Background and Aim:: Food-borne pathogens are causing a great number of diseases with remarkable effects on human health. Mentha pulegium has several biological uses e.g. antimicrobial, antioxidant and antispasmodics, in good correlation with the high contents of phenolic compounds. The aim of the current study was to assess the effects of Mentha pulegium essential oil (MPO) alone and in combination with nisin against Staphylococcus aureus in commercial barley soup stored at refrigerated temperature during 14 days.Methods:Gas chromatography-mass spectrometry analysis of MPO was performed. A commercial barley soup was prepared according to the method described by producer manual. It contained barley, onion, salt, vegetable oil, parsley, yeast extract, carrot, monosodium glutamate, citric acid and spices. After preparation, the samples were inoculated with 5 log CFU/ml of S. aureus. Then, concentrations of MPO (0, 0.1, 0.2 and 0.4%) separately and in combination with nisin (0 and 100 IU/ml) were added into the barley soups.Results:Based on our findings, pulegone (77.32%) and l-menthol (11.11%) were the major compounds of the MPO. The following sequence inhibition effect on S. aureus was observed in treated soups: MPO 0.4% + nisin 100 IU/ml > MPO 0.2% + nisin 100 IU/ml > MPO 0.1% + nisin 100 IU/ml > MPO 0.4% > MPO 0.2% > MPO 0.1% > nisin 100/ml.Conclusion:The results of the present study demonstrated that antibacterial effects of different concentrations of MPO separately and in combination with were effective in inhibition growth of S. aureus inoculated to the commercial barley soup.

Keywords:

Mentha pulegium essential oil , Nisin , Staphylococcus aureus , commercial barley soup