No abstract

The effect of different concentrations of Zataria multiflora Boiss. essential oil (EO; 0%, 0.005%, and 0.015%), nisin (0, 0.125, and 0.25 microL/mL), and their combinations on the production of staphylococcal enterotoxin C (SEC) and alpha-hemolysin (alpha-toxin) by Staphylococcus aureus at different inoculation levels (10(3), 10(4), and 10(5) cfu/mL) in brain heart infusion broth during storage at 35 degrees C for up to 43 days was evaluated. The SEC production was significantly (p < 0.05) inhibited and the hemolysis due to alpha-toxin was significantly (p < 0.05) reduced by EO concentration at levels 0.015% and 0.005%, respectively. Significant (p < 0.05) inhibitory effect of EO on SEC production at level 0.005% was observed when it was used in combination with nisin = 0.125 microL/mL. The significant (p < 0.05) synergistic effect of EO = 0.005% and nisin = 0.125 microL/mL was also observed as more reduction of hemolysis due to alpha-toxin than EO = 0.005% alone. Further, EO significantly (p < 0.05) prevented SEC production by S. aureus during the manufacturing process of a traditional Iranian white brined cheese (as a food model) even at its lowest concentration (5 microL/100 mL), in this study.

Yoghurt is a popular dairy product in Iran because of its beneficial influence on human health and nutritional value. Aflatoxin M1 (AFM1) is the metabolite of potential carcinogen aflatoxin B1, which can contaminate milk through the feed and is not eliminated by common processing heat treatment. An analytical method using immunoaffinity column for extraction and a high-performance liquid chromatography (HPLC) for quantification was developed for AFM1 in this study. An HPLC method with fluorimetric detection for the determination of AFM1 in yoghurt milk has been optimized and validated according to Commission Decision BS EN ISO 14501: 2007 by using the conventional validation approach. The procedure for determining selectivity, recovery, precision, decision limit (CCα) and detection capability (CCβ) of the method has been reported. The results of the validation process demonstrate the agreement of the method with the provisions of Commission Regulation 401: 2006:EC. A new HPLC method with fluorescence detection was developed to determine aflatoxin M1. The detection limit was 1 ng/kg for yoghurt. The calibration curve was linear from 0.1 to 3.0 μg l⁻¹ injected. The method includes a preliminary clean-up and the average recoveries determined on three different days at the concentration levels of 0.025, 0.050 and 0.075 μg kg⁻¹ were in the range of 72.57%-86.66% with RSD in the range of 2.56%-8.41%. The interday and interlevel mean recovery value, which has been used to correct routine analysis results, was 80%. The method is rapid, easily automatable and therefore useful for accurate and precise screening of aflatoxin M1 in yoghurt.

Q fever is a widespread zoonosis caused by the obligate intracellular micro-organism Coxiella burnetii. The objective of this study was to determine the prevalence rate of C. burnetii in bulk milk samples from dairy bovine, ovine, caprine, and camel herds in Isfahan province, Iran. In the present study, 567 bulk milk samples from 186 dairy bovine, ovine, caprine, and camel herds were tested for C. burnetii using a nested polymerase chain reaction assay. The animals whose milk samples collected for this study were clinically healthy. In total, 8 of 247 (3.2%) bovine milk samples were positive; the positive samples originated from 6 of 90 (6.7%) dairy herds. Eight of 140 (5.7%) ovine bulk milk samples from 42 sheep breeding farms and 5 of 110 (4.5%) caprine bulk milk samples from 32 goat breeding farms were positive for C. burnetii. One of 70 (1.4%) camel bulk milk samples from 22 camel breeding farms was also positive for C. burnetii. Although no extensive prevalence study was undertaken, the results of this study indicate that clinically healthy dairy animals are important sources of C. burnetii infection in Iran. To the authors' knowledge, this study is the first report of direct identification of C. burnetii using polymerase chain reaction in bulk milk samples from dairy ovine herds in Iran and the first report of direct identification of C. burnetii in bulk milk samples from dairy camel herds. Further intensive prevalence studies on Coxiella infection and on possible risks of dairy products will be needed to elucidate the epidemiology of Q fever in Iran.

A total of 150 samples of hamburgers (120 raw and 30 cooked) from different retail stores in Tehran were examined bacteriologically for total aerobes, total coliforms, Staphylococcus aureus, and Salmonella. Attempts to isolate any Salmonella from both cooked and raw hamburgers failed. It was shown that heat treatment had a significant effect on the bacteriological quality of the hamburgers.

Aflatoxin M1 (AFM1) was determined by enzyme linked immunosorbent assay in 88 samples of traditional cheese consumed in Esfahan city of Iran. In 47 of 88 samples (53.4%), the presence of AFM1 was detected in concentrations between 82 ng/kg and 1254 ng/kg. The mean level of AFM1 of positive samples was 412 ng/kg. AFM1 in 28 (31.8%) samples was higher than the maximum tolerance limit (250 ng/kg) accepted by some countries. Statistical analysis showed that there were no significant differences (P>0.05) between the mean concentrations of AFM1 in cheese samples of spring, summer, autumn and winter. However, the mean concentration of AFM1 in cheese samples from spring and summer was significantly lower than autumn and winter (P=0.05). It can be concluded that the high occurrence of AFM1 in cheese is probably due to the presence of aflatoxin in the feed and cheese milk. This condition should be considered as a probable hazard for human health.

Nanopackaging is one of the most significant subjects in food packaging And it is so important for food safety and food quality control, then we need natural method (without chemical material)for packaging process. In this study, the possibility of using nanocomposite (LDPE) based on silver nanoparticle as a food packaging was proposed. Chemical reduction method with Trisodium citrate as a reductant was applied for preparing silver nanoparticle. In the method mentioned using of diverse reducing agent can be produced different size of nanoparticles that having different antibacterial action. The nanostructure and particle size of of silvernanoparticles were confirmed by scanning electron microscopy(SEM). The average of particle size was 68 nm. After confirming the formation of nanoparticles, they were coated on the LDPE surface by melt mixing method. Surface morphology of the silver/LDPE nanocomposite was characterised by Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX) and X-ray Photoelectron Spectroscopy (XPS). The film thickness was 33.67nm. In addition, the antibacterial properties of the prepared nanocomposite film was evaluated by disc diffusion method. The results showed avourable antibacterial efficiency against Escheria Coli (ATCC 8739) and staphylococcus aureus(ATCC 6538) and The results show that the released silver from the coated film is enough to create antimicrobial activity in the incubated solution.

No abstract