Antimicrobial effects of Mentha spicata essential oil and methanolic carrot extract against Staphylococcus aureus and Listeria monocytogenes in fish soup

Plant essential oils and natural extracts have been attracted research interest to control bacterial contamination of food products. Staphylococcus aureus and Listeria monocytogenes are considered as public health bacterial hazards which survive in various types of food. The aim of the current study was to assess the effects of Mentha spicata essential oil (MSO: 0, 0.1 and 0.2%) alone and in combination with methanolic carrot extract (MCE) (0, 0.25 and 0.5%) against S. aureus and L. monocytogenes in fish soup. Untreated and treated homemade fish soups with different concentrations of MSO and MCE were inoculated with 5 log CFU/ml of S. aureus and L. monocytogenes, and then stored at 4 ± 1 ˚C (refrigerated temperature), 9 ± 1 ˚C (abused temperature) and 25 ± 1 ˚C (room temperature) during 15 days. Based on these findings, carvone (78.76%) and limonene (11.50%) were the major compounds of the MSO. The following sequence inhibition effect on S. aureus and L. monocytogenes was observed in treated soups: MSO 0.2% + MCE 0.5% > MSO 0.2% + MCE 0.25% > MSO 0.2% > MSO 0.1% + MCE 0.5% > MSO 0.1% + MCE 0.25% > MSO 0.1% > MCE 0.5% > MCE 0.25%. The results of the present study demonstrated that antibacterial effects of different concentrations of MSO separately and in combination with MCE were higher at 4 and 9 ˚C than 25 ˚C.