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Background and objectives: Chitosan is a preservative that is commonly used in food packaging due to forming a film with antimicrobial activity. Many antimicrobial agents have been used to control the growth of different bacteria, fungi and yeasts in food products using chitosan coating. The present research was conducted to examine inhibitory effects of a coating incorporated with the essential oils of Zataria multiflora (ZEO) and Bunium persicum (BEO) on the growth of Pseudomonas artificially inoculated onto salmon fillets over a period of 12 days at 4 °C.
Methods: The antibacterial activity of BEO against P. aeruginosa was evaluated using the microdilution method via determining minimum inhibitory concentration and minimum bactericidal concentration. For the food model investigation, three P. aeruginosa strains were inoculated onto trout fillets as culture cocktail to assess their survival over 12 days of storage.
Results: The results indicated that ZEO and BEO had stronger inhibitory effect on P. aeruginosa in trout fillets when applied along with gel type nano-emulsion of chitosan solution. The separate use of each of these substances also significantly inhibited the growth of these pathogenic bacteria compared with the control. In addition, the use of chitosan coating without any antimicrobial agent affected the growth of P. aeruginosa.
Conclusion: The gel type nano-emulsion of chitosan coating containing ZEO and BEO can be applied on foodstuff, particularly fish and its products, as an antimicrobial agent.

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Background and objectives: Neutralized electrolyzed water (NEW) is a novel natural disinfectant. It has been suggested that application of NEW can improve the shelf life of fish. This study aimed to investigate effect of NEW incorporated in alginate coating on growth of Escherichia coli O₁₅₇: H₇ on salmon fillets over a period of 12 days.
Methods: Fish fillets were inoculated with E. coli O₁₅₇:H₇ and divided into six different treatment groups: control (no coating), distilled water, alginate, EW, EW & alginate (Samples coated with alginate solution prepared by EW), and EW+ alginate (samples immersed in EW, then coated with alginate solution). The fillets were kept at 4 °C, and the bacterial count was determined on days: 0, 2, 4, 8, and 12. Data analysis was performed using repeated ANOVA and Bonferroni post-hoctest at statistical significance of 0.05.
Results: Treatment with alginate coating and EW alone could significantly reduce E. coli O₁₅₇: H₇ count on the salmon fillets. However, maximum reduction (1.27 log CFU/g) of bacteria was achieved when using alginate coating combined with EW.
Conclusion: According to the results, the combination of alginate coating with EW can be applied as a natural antimicrobial for increasing safety of food products, especially fish, against pathogenic bacteria such as E. coli O157: H7.