Effect of alginate coatings containing Zataria Multiflora Boiss essential oil in forms of coarse emulsion and Nano-emulsion on inoculated Escherichia coli O157:H7 in beef fillets

The present study was carried out to compare the inhibitory effect of alginate coatings containing Zataria Multiflora Boiss essential oil (ZMEO) in two forms of coarse emulsion and Nano-emulsion on the growth of inoculated Escherichia coli O157:H7in beef fillet during 16 days of refrigeration (4 C °). Accordingly, alginate solutions (3%) with different concentrations of ZMEO (0.25%, 0.5% and 1%) were prepared and coarse emulsion and Nano-emulsion forms were then prepared. Beef fillets after being inoculated by Escherichia coli O157:H7 (1.5×105 log CFU/g) were immersed in different alginate treatments and bacterial count was performed during refrigeration on days: 0, 4, 8, 12 and 16.Results indicated that alginate coating containing ZMEO in both forms (coarse/Nano-emulsion) is a proper candidate to control E. coli O157:H7   at 4 C °; however higher antibacterial effect (P <0.05) was observed in samples treated by Nano-emulsion form than coarse emulsion when they were compared to control. The lowest bacterial growth was observed in samples coated with alginate Nano-emulsion containing 1% ZMEO (5.3 ± 0.24 log CFU/g) at the end of storage.  Accordingly, applying alginate coatings containing ZMEO particularly in the form of Nano-emulsion, can effectively decrease the growth of E. coli O157:H7 during storage; therefore, It is natural additive which can be chosen to be applied in food industry specially meat industry.