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As natural antioxidants and antimicrobials, essential oils (EOs) have been increasingly used to control foodborne pathogens. However, the application of EO in the food industry is limited due to low water solubility, intensive flavor, and high volatility. Therefore, to enhance water dispersion and prevent EO from degradation, nanoemulsions may be an alternative. In this study, two types of thyme essential oil (TEO) nanoemulsions, with distilled water (NEO) and with cinnamon aqueous extract (NEOC), were prepared. The physical, antimicrobial and antioxidant properties of TEO extracts and nanoemulsions were determined. The results showed that the mean particle size and PDI index of NEOC and NEO were 728.2 and 162.4 nm and 0.19 and 0.30, respectively. Polyphenolic compounds of aqueous extract of cinnamon, TEO, NEO and NEOC were in the range of 33.4 to 10.9 mg gallic acid equivalent/g. The antioxidant activity (DPPH) was in the range of 16.3 to 66.4%. Phenolic compounds and DPPH, TEO and NEOC were the highest. Also, the antimicrobial effects of NEO and NEOC against Staphylococcus aureus and Salmonella Typhimurium were significantly higher than TEO and cinnamon aqueous extract. The lowest values of MIC and MBC were first related to NEOC and then to NEO, which indicates the greater sensitivity of the studied microorganisms to nanoemulsions. According to the results, the highest antimicrobial and antioxidant activity was related to NEOC nanoemulsion. Therefore, it can be used in food products to prevent food poisoning and to treat diseases caused by S. aureus and S. Typhimurium.

Due to the increasing need to gain knowledge about the inhibitory effects of plants, in this study, the antimicrobial effects of Carum copticum, Rosa damascene, Anethum graveolens and Cuminum cyminum essential oils on some bacteria and yeast were investigated. The essential oils were extracted using a Clevenger apparatus and their compounds were determined by gas chromatography equipped with a mass spectrometer. Also, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of the essential oils were determined and their antimicrobial properties were compared by well-diffusion method. MIC results of Bacillus cereus and Staphylococcus aureus showed that Cuminum cyminum essential oil with 50 µg/ml had the lowest bactericidal effect. The essential oils of Carum copticum, Anethum graveolens and Rosa damascene had the highest bactericidal effect with 0.78 μg/ml on the studied bacteria. In the case of Escherichia coli, the highest antimicrobial effect was shown by Carum copticum essential oil at 6.25 μg/ml. Rosa damascene essential oil, with a concentration of 3.12 μg/ml, had the highest antifungal properties on Candida albicans. In the case of Saccharomyces cerevisiae, the most antifungal effect was provided by Rosa damascene and Cuminum cyminum essential oils with 0.78 μg/ml. The antibacterial effect of Carum copticum essential oil was higher than the other three essential oils. In the case of yeasts, Rosa damascene and Cuminum cyminum essential oils had the most antifungal effect. According to the results, Carum copticum essential oil in controlling bacteria and Rosa damascene essential oil in controlling studied yeasts are recommended.

Listeria monocytogenes (Lm) is an important foodborne pathogen that is of great importance in milk and its products. Despite the measures taken to eliminate and control Lm contamination in pasteurized milk products, but due to its high spread in the environment, there is a possibility of secondary contamination in products such as Ultra-filtered (UF) white cheese. This study aimed to investigate the inhibitory effect of nisin-producing Lactococcus lactis on Lm in Ultra-filtered white cheese. Ultra-filtrated and pasteurized cow's milk was inoculated with 3 Log CFU/g of standard or native strains of Lm and control and treatment (containing nisin-producing L. lactis) cheese samples were manufactured. Changes in the population of Lm and nisin concentration were estimated throughout the storage period. According to the results, in all groups, the population of Lm began to decrease from day five onwards. Nonetheless, the decreasing trend in the treatment samples and in parallel with the production of nisin was significant (p < 0.01). The native strain of Lm was significantly (p < 0.01) more resistant than the standard one. Since the nisin-producing L. lactis, despite inhibiting Lm, did not negatively affect the growth of starter bacteria and the resulting pH decline of the cheese samples. Consequently, nisin-producing L. lactis can be used to control some bacterial contamination of the UF white cheese. It is also necessary to study the behavior of native strains isolated from food samples along with laboratory strains in inoculation studies.

Enterococci are among lactic acid bacteria that are homogeneous and are commonly found in raw milk and its products. The purpose of this study was to isolate Enterococcus species from raw milk and traditional milk products in Tabriz region and to study their inhibitory effect on some of pathogenic bacteria. For this, 105 specimens including 15 samples of each of raw milk, yogurt, cheese, cream, butter, dough, and whey were tested. After isolation and differential identification of the species, 24 isolates were selected based on the sample type and the variety of Enterococcus species. Due to the pathogenic potential of E. faecalis and E. fascism species, they were evaluated for the presence of Esp and Asa1 genes, respectively. The inhibitory effect of Enterococcus isolates was tested on nine important foodborne pathogens using overlay method. According to the results, nine species of E. fascism, E. faecalis, E. gallinarum, E. avium, E. Benedetti, E. caseliflavus, E. hirae, E. saccharoliticus and E. raffinosus were isolated. All isolates had an inhibitory effect on indicator organisms; however, the inhibitory effect was found different among various species and various strains. E. faecalis and E. fascism species had the most antibacterial effects. The molecular evaluation showed that out of 5 isolates of E. faecalis, 2 isolates contained Esp gene. In the case of E. faecalis, none of the isolates harbored Asa1 gene. If further experiments are carried out in relation to the proven safety of enterococci, their inhibitory effect on food pathogenic bacteria can be used.

Bacillus is the dominant genus encloses gram-positive spore-formers that some are considered as a threat to the quality of foods and consumers’ health. This study aimed to explore the occurrence of Bacillus species in raw milk tankers and dairy processing equipments as well as to examine the biofilm-forming ability of the isolates. For this reason, a total of 80 samples consisting of 30 samples obtained from raw milk tankers, 30 samples of dairy processing equipments and 20 samples from various surfaces of the production plant was collected. According to the results, 16.66% of the samples obtained from raw milk tankers, 20% of dairy processing equipments and 40% of surface samples were found positive for Bacillus species. Various species of the Bacillus were found; amongst B. cereus with 36% and B. aloe and B. pumilus with 4% occurrence rate, were the most and least abundant species, respectively. Results of biofilm production revealed that 96% of the isolates were capable of producing biofilm. Eventually, it was concluded that conventional CIP procedure is unable to entirely remove the biofilm of Bacillus species from dairy plant surfaces. Hence, there is a need for a new approach to conquer the problem.

Herbs are often produced by traditional methods and in poor sanitary conditions and can contain high amounts of spoilage and pathogenic microbes. The aim of this study has investigated the effect of ozone on some qualitative characteristics and microbial spices sumac, cumin and pepper. For this purpose, samples were treated by ozone at a concentration of 2 g per hour for 10, 20, 40 and 60 minutes. Then microbial count and chemical characters such as moisture content, antioxidant properties, and phenolic compounds were determined. The results showed that compared with controls, treatment with ozone decreased 2 logarithmic units (P

This study aimed to investigate the prevalence of Staphylococcus aureus in raw milk and traditional dairy products of West-Azerbaijan Province and also to evaluate the presence of TSST-1 virulence gene, antibiotic resistance and biofilm formation of the isolates. Using stratified random method, a total of 80 raw milk and traditional dairy products (including traditional cheese, cream and curd) together with 20 nasal swab samples of the dairy products’ manufacturers were collected. S. aureus strains were isolated and identified by conventional culture methods. Afterwards, the isolates were subjected to PCR analysis to detect the presence of TSST-1 gene. According to the findings, 35% of the samples were contaminated by S. aureus. Moreover TSST-1 gene was recognized in 1 cheese and 2 swab samples. Antibiotic resistance profile revealed that most of S. aureus isolates were resistant towards vancomycin, penicillin, and methicillin and sensitive towards co-trimoxazole, gentamicin, rifampin, oxacillin, and cephalothin. Moreover, 2.85%, 17.15%, and 80% of the isolates were capable to form high, moderate and low amounts of biofilm. High occurrence of S. aureus in milk and dairy products which harbor TSST-1 virulence gene, and the strains that demonstrated resistant to several antibiotics and capable of biofilm formation, could be considered a health threat to the consumers of these products.