The aim of this study was to test the reliability of commercial ELISA tests (RC-bovino) within raw and heat treated cow milk detection in sheep milk and cheese in order to obtain a high-quality, reliable and economically beneficial method suitable for routine application in practice. These tests were subsequently used for quantification of cow milk in commercial "Bryndza". Raw sheep milk, cow milk and heat-treated cow milk (pasteurisation at 72 °C for 15 sec or at 85 °C for 3 sec) were mixed in precisely defined proportions (0 -100% cow milk in sheep milk). The milk mixtures were sampled to detect adulteration and subsequently cheese was made. By ELISA tests was possible to determine these amounts of raw cow milk in sheep milk: 0.5% (0.2%), 5 % (4.81%), 50% (42.08%) and 75% (56.52%). The pasteurized samples in different combinations gave lower optical density responses than those prepared from raw milk (by approximately 60%). In context with the above mentioned, the relationship between the real and detected amount of cow milk (%) in different production stages (milk, cheese) using a regression analysis was examined. However, a lower reliability of the detection was indicated by R 2 values, which ranged from 0.4058 (cheese) to 0.5175 (milk). In practice this means that although individual percentage (%) of cow milk in the sample can be detected, but in the unknown sample it can not be clearly confirm whether the cow milk was raw or heat-treated. In this context, the results can be inaccurate and may not correspond to the real situation. Within monitoring phase of this research, 9 samples of bryndza were analysed with the results of detected cow milk ranged from 11.56% to 14.3%. The obtained results confirm that the appropriate selection of ELISA tests can become an important factor in the setting of analytical capabilities for the detection of milk and cheese adulteration.

The aim of this study was to follow contamination of ready-to-eat food with Listeria monocytogenes by using the Step One real time polymerase chain reaction (PCR). We used the PrepSEQ Rapid Spin Sample Preparation Kit for isolation of DNA and MicroSEQ® Listeria monocytogenes Detection Kit for the real-time PCR performance. In 30 samples of ready-to-eat milk and meat products without incubation we detected strains of Listeria monocytogenes in five samples (swabs). Internal positive control (IPC) was positive in all samples. Our results indicated that the real-time PCR assay developed in this study could sensitively detect Listeria monocytogenes in ready-to-eat food without incubation.

The object of the research was to investigate the quality of vegetable oils for cooking food. The analysis used two types of oils - oil Fritol and Promienna. Both oils were purchased commercially. Oil changes were observed at frying French fries. At the same changes were observed oil stored at room temperature and the temperature in the refrigerator. The determined parameters included the measurement of polar materials in oil with electronic device Testo 265 for measuring the quality of cooking oil. Determination of change in the texture of oil during the oil deterioration by device Texturometer TA.XT Plus and determination the peroxide value by STN EN ISO 3960:2007. The work is also evaluating the results of the studied parameters. In all compared cases based on the content of the TPM showed higher heat resistance oil Fritol and sample of oil stored in the refrigerator.

doi:10.5219/210

ABSTRACT:The direct fluorescence microscopy method with ethidium bromide staining can be used for somatic cell counting in raw cow's milk. However, this method has some limitations that may influence the results of the analysis. We therefore aimed at improving the procedure of somatic cell nuclei staining. We tested the hypothesis that ethidium bromide can better penetrate into the DNA of cells with degraded somatic cell walls or into dead cells. Therefore, we increased the temperature of the sample to 100 °C in order to disrupt the somatic cell wall membrane and to improve ethidium bromide penetration to somatic cell nuclei. In all, 90 samples of raw cow's milk were analysed in this experiment. Three parallel measurements were performed using each of the microscopic methods and the routine flow cytometry method. In all, 810 microscopic smears were analysed. The somatic cells were counted using fluorescence microscopic methods and flow cytometry. The increased temperature during the sample preparation improved (P < 0.005) the penetration of ethidium bromide into the somatic cell nuclei. It is concluded that the direct fluorescence microscopy method is suitable for precise laboratory analysis of somatic cell in raw cow's milk.

The objective of the study was to investigate potential adulteration of commercial caprine milks and cheeses with bovine milk using commercial qPCR assay. The assay comprised of bovine-, ovine-and caprine-specific primers and TaqMan probe and mammalian internal control. Specificity, sensitivity, linearity, reproducibility and efficiency of the bovine assay were tested as well. Specificity was verified by running reaction on the DNA of other milk-producing species (caprine and ovine) and made-up bovine-caprine (v/v) milk mixes. In both experiments, a bovine DNA fragment was amplified whereas no amplification was obtained from the other species. Sensitivity, linearity, reproducibility and efficiency were tested on 10-fold dilution series of 10 ng bovine DNA. The assay has shown good linearity (R 2 = 0.983) within whole range, with efficiency of 86% and excellent reproducibility (SD around the C T for the technical replicates <0.5). The sensitivity was adequate, as calculated LOD and LOQ were 1.44 pg and 2.94 pg of bovine DNA, respectively. Finally, the assay was used to authenticate 5 caprine milk samples and 5 caprine cheese samples, purchased from local supermarkets. Totally, 1 milk sample has shown the fluorescence signal, which exceeded baseline in cycle 39.01 ±0.69. However, the signal was above LOD and LOQ suggesting that there could not be unambiguously declared any adulteration with bovine milk. Amplification of bovine-specific DNA was not observed in the other samples indicating products were not adulterated. The commercial qPCR assay has proved that real-time PCR assays, as well as DNA-based techniques in a general, are the excellent and reliable tools for fighting with frauds in the food industry and protecting the public health.