Combination of trans-cinnamaldehyde or eugenol with nisin for inactivation of L. monocytogenes

Abstract

Effect of combination of nisin with trans-cinnamaldehyde or eugenol against L. monocytogenes was evaluated in milk and unripened cheese as model. Antilisterial activity of alone or combination was initially determined in broth. A standard checkerboard assay was applied to know type of interactive effect between them using FIC index. Further Log DP method was followed to know combination of antimicrobials effect in milk with fat <0.5%, 1.5% and 3% and in unripened cheese spiked with target pathogen. The results indicated that MBC of nisin with trans-cinnamaldehyde or eugenol in skim milk was 400 IU/ml, 2.1 mg/ml and 4.3 mg/ml, respectively revealed synergistic effect for combinations nisin with trans-cinnamaldehyde or eugenol according to FIC index. A stronger inhibition in terms of Log DP was displayed by combinations than alone in milk with different levels of fat and unripened cheese. The significant increase in cell constituents was observed as a result of combination treatments. Furthermore, observation of antimicrobial treated cells under transmission electron microscopy revealed extensive damage to the cell membrane of bacteria. The finding of this study this gives possibility to explore multi preservative approach by exploiting synergistic interactions of antimicrobials to increase antibacterial activity of essential oil at lower doses.