The main functions of nitrite, which is the most frequently used additive in meat products, are to develop typical taste and aroma of cured meat, to prevent lipid oxidation, to create the typical color of cured meat production by reacting with myoglobin, and to produce an antimicrobial effect (Marco et al., 2006). However, since nitrite causes the formation of carcinogenic N-nitroso compounds, the studies concentrated on other additives (Zarringhalami et al., 2009). Studies were carried out on the alternative additives, which fulfill various functions of nitrate and nitrite in the processed meat products such as antimicrobial, anti-oxidative, and colorization effects formation and which pose a lower level of health risk in comparison to nitrate and nitrite (Öztürk et al., 2015). Since nitrate/nitrite has various functions in meat, no single additive that could fulfill all these functions could be found. Besides decreasing or preventing the use of nitrite in meat products by making use of natural elements, organic acids, irradiation, pressure applications, and hazard technology were also investigated in the previous studies (Turp & Sucu, 2016).Thyme is an important herb, thanks to its high thymol concentration. Previous studies revealed the anti-oxidative, antimi-

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mg/kg Se respectively. Certified reference material (NIST CRM 2976 muscle tissue) was analyzed for accuracy of method. This results are good agreement (≥95 %) with the certified values.

The use of bacteriocins in protecting the foods has significantly increased in recent years. Nisin is an important bacteriocin and is a food preservative additive safely used in food industry. In the present study, it was aimed to investigate the effect of nisin, which is an alternative to the synthetic additives, on the growth of milk-derived Staphylococcus aureus strains in the cheese. For this purpose, 100 different milk specimens were obtained, transferred using cold chain (at 0-4°C), and inoculated to Baird-Parker agar. At the end of inoculation process, 37 suspicious colonies were selected and coagulase-positive Staphylococcus aureus was detected. The strains obtained were passaged to the pre-enriched agars and the intensities of the strains were determined according to McFarland. Besides these strains, the coagulase-positive Staphylococcus aureus strains obtained from Etlik Veterinary Microbiology Institute were inoculated into each specimen at 10 4 CFU mL-1 concentration. The cheese production was made using milks containing the strains, which were isolated from the milk, and the standard strains at different concentrations. The specimens obtained from cheeses produced from milk containing using standard strains were divided into groups K, A, B, and C containing 0, 100, 200, and 400 IU mL-1 nisin, respectively. Similarly, the specimens obtained from cheeses produced from milks containing milk-derived strains were divided into groups K1, A1, B1, and C1 containing 0, 100, 200, and 400 IU mL-1 nisin, respectively. The procedures were triplicated. Staphylococcus aureus counting on the cheese specimens were performed on 1 st , 6 th , 12 th , and 24 th hours from curd to ball and on 5 th , 10 th , 20 th , 30 th , and 40 th days of storage at +4°C. In conclusion, it was observed that the nisin inhibited the growth of all the Staphylococcus aureus strains. However, it was also determined that the inhibition of milk-derived Staphylococcus aureus strains were higher than the inhibition of standard strains.

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