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Plant essential oils can prevent the growth of bacteria and increase the shelf life of food products such as seafood and fish. In this study, the effect of zizphora and tarragon essential oils at concentrations of 500, 1000, and 2000 mg/L on microbial quality and shelf life of rainbow trout fillets stored at 4 ºC was investigated. The results showed that the essential oils of ziziphora and tarragon were effective in reducing the production of volatile nitrogen bases and the greatest effect was related to ziziphora essential oil with a concentration of 2000 mg/L. It was also observed that the use of ziziphora and tarragon essential oils reduced the total viable counts, psychrotrophic bacteria, coliforms, and Escherichia coli bacteria compared to the control sample, which confirms their antimicrobial properties. It was concluded that ziziphora essential oil with a concentration of 2000 mg/L was more effective than tarragon essential oil in controlling the microbial load and delaying the spoilage of rainbow trout fillet at refrigerator temperature.

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Excessive use of antibiotics in the animal husbandry causes the accumulation of their residual amounts in food of animal origin such as dairy products. Since the consumption of these foods has a negative effect on human health, authorized organizations such as the European :union: have set maximum residue limits (MRLs) for antibiotics in food of animal origin. This research aimed to present a magnetic ionic solvent based extraction procedure for preparation and preconcentration of tetracycline, oxytetracycline and enrofloxacin residues in cheese samples and their determination by high-performance liquid chromatography equipped with a diode array detector. For this, the effect of various parameters on the extraction efficiency was investigated and optimized. The results showed that the residual amounts of oxytetracycline and tetracycline in 4 and 5 samples of the tested cheeses, respectively, were determined above the permissible limits. Enrofloxacin residue was not found in any of the samples. From the advantages of the proposed extraction method, we can point out the high separation power and the possibility of highly sensitive analyzing of mixed analytes, so that under optimized conditions, the recovery percentage ranges were 80-91. The limits of detection and quantification were respectively less than 1.8 and 6 ng/g, which is much lower than the MRLs set for target antibiotics in cheese (100 ng/g).