Ivana Borkovcová’s research while affiliated with University of Veterinary Sciences Brno and other places

The presence of antibiotics in milk is a significant problem affecting the technological safety of dairy products. The aim of the study was to determine the sensitivity of yoghurt cultures to residual levels of selected cephalosporin antibiotics (cephalexin, cefoperazone, cefquinome, cefazolin, and ceftiofur). Five yoghurt cultures were selected containing strains of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. Artificially fortified milk samples (whole pasteurized milk; 85 °C; 3–5 s) with cephalosporins at a concentration of the maximum residue limit were used to evaluate the sensitivity of the yoghurt cultures by monitoring the pH, titratable acidity, and the concentration of selected organic acids (lactic, pyruvic, citric, acetic, orotic, oxalic, formic, uric, and succinic acids) at the end of fermentation (43 °C; 4–5.5 h; pH ≤ 4.6). The titratable acidity was determined by the Soxhlet–Henkel method and the organic acid concentration was monitored by reversed-phase HPLC. Ceftiofur had the greatest effect on the yoghurt culture activity, with a statistically highly significant effect (p < 0.05) on the pH, titratable acidity, and the content of lactic, pyruvic, and acetic acids in all cultures. Other cephalosporins also showed an inhibitory effect on yoghurt metabolism as seen by the evaluation of the lactic and pyruvic acid concentrations.

Honey is a popular sweetener that makes significant contributions to human nutrition. The aim of this study was to analyze and compare specific properties relating to honey quality and biological value such as total phenolic content, color, color intensity, proline and other quality parameters like moisture content, electrical conductivity, 5-hydroxymethylfurfural, diastase activity in various honeys directly from beekeepers and from markets. In total fiftysix honey samples directly from Czech and Slovak beekeepers (n=25) and from markets in the Czech Republic (n=31) were collected during 2018. The determined parameters varied depending on the botanical and geographical origin of honeys. The identified most significant differences (p < 0.01) between the analyzed beekeepers and market honeys in color, color intensity, total phenolic content, moisture content and 5-hydroxymethylfurfural point to the different properties and impact of honey processing on honey composition. In several parameters, like color, color intensity, total phenolic content, proline content and electrical conductivity a very good correlations with botanical origin of honey were observed and beside the melissopalynological analysis these parameters participated on characterization and authentication of unifloral honeys. Normally, there is a positive correlation between color and electrical conductivity, however we have also confirmed that the color of honey also depends on the proline content. The results of this study confirmed that the origin (beekeeper/market) and botanical source of honeys (unifloral/nectar/honeydew) had effect on their quality and biological value. © 2022. Emirates Journal of Food and Agriculture. All Rights Reserved.

Yoghurts from cow, goat and sheep milk were produced and stored under defined conditions to monitor the influence of various factors on the benzoic acid content as determined by Ultra High Performance Liquid Chromatography (UHPLC). The highest level of benzoic acid was found in sheep yoghurt (43.26 ± 5.11 mg kg−1) and the lowest in cow yoghurt (13.38 ± 3.56 mg kg−1), with goat yoghurt (21.31 ± 5.66 mg kg−1) falling in between. Benzoic acid content did not show statistically significant variation until the second and third weeks of storage, and the dynamics of this variation varied depending on the type of yoghurt. The yoghurt culture containing different strains of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus also affected the contents of benzoic acid. Further, the different storage temperatures (2 and 8 °C) as well as the temperatures used to milk heat treatment before yoghurt production (80, 85 and 90 °C) affected the amount of benzoic acid in different types of yoghurts.

The aim of the study was to contribute to scarce literature data on the content of selected vitamins and iodine in mare’s milk. The study focused on the content of selected lipophilic vitamins (A, E), hydrophilic vitamins B 1 , B 2 , B 6 ) and iodine in milk samples obtained from 8 mares during 6 months of lactation. The content of micronutrients was evaluated according to the stage of lactation. Vitamins B 2 and B 6 were determined using ion-pair reversed phase high performance liquid chromatography with fluorescence detection, vitamin B 1 by fluorescence detection by reversed-phase liquid chromatography, vitamins A and E by the ultra-high performance liquid chromatography method with ultraviolet and fluorescence detection and iodine by the spectrophotometric method. Mean concentrations of vitamins A (0.06 ± 0.08 mg/l), E (0.083 ± 0.14 mg/l), B 1 (256.24 ± 44.19 µg/l), B 2 (111.40 ± 81.88 µg/l), B 6 (0.30 ± 0.12 mg/l) reached lower values in mare’s milk compared to cow’s milk. The mean value of iodine in mare’s milk reached 44.48 ± 54.45 µg/l. Lactation stage proved to be a significant factor for vitamin B 6 and iodine.

In this study, we determined four sulfonamide compounds (sulfadiazine, sulfadoxine, sulfamethoxazole, and sulfathiazole) in honey marketed in the Czech Republic (Brno). The content of these compounds was monitored in 50 honeys with different botanical and geographical origin. Preanalytical treatment included acidic hydrolysis with 10% trichloroacetic acid (TCA) and double extraction with acetonitrile and dichloromethane. Chromatographic analysis was performed by ultraperformance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS) using a triple quadrupole (QqQ) in positive ionization mode (ESI ⁺ ). For separation, the mobile phase was a 0.05% aqueous solution of formic acid (A) and 0.05% formic acid in methanol (B) with a gradient elution of 0–3 minutes: 10% B; 3–3.6 min: 90% B; and 3.6–5 min: 10% B, flow rate 0.30 ml/min. Three positive samples (6%) were found containing sulfadiazine (232.88 and 618.87 μ g/kg) and sulfamethoxazole (62.64 μ g/kg). According to the country of origin, two of these honeys were from European Union (EU) countries, and one was labeled as a blend of honey from EU and non-EU countries.

The aim of the study was to monitore the levels of fluoroquinolone residues in bulk samples of raw cow’s milk. The bulk samples of raw cow’s milk (n = 150) were obtained from 58 different milk suppliers in the South Moravian and Vysočina Regions. The samples were analysed by reverse phase high-performance liquid chromatography method with fluorescence detection and gradient elution. 87.3% of the raw milk samples were positive for the fluoroquinolones residues. Flumequine was present in none of the samples. The levels of other fluoroquinolones investigated were below the recommended maximum residue limit. The results of the study indicate that fluoroquinolones are frequently administered to the dairy cows in spite of the recommendations of CVMP. The most frequently determined was enrofloxacin and its indicator residue, i.e. ciprofloxacin. An efficient control of the veterinary drugs residues in milk is very important to ensure the safety of the milk and milk products.

The aim of this study was the determination of lactoferrin in goat milk using HPLC method. Milk samples were collected at a goat farm in the South Moravia Region, the Czech Republic. It were established bulk tank samples of raw milk ( n = 24) and pasteurised milk ( n n = 27) that were collected during lactation. Lactoferrin contents were analysed by reverse phase high-performance liquid chromatography (RP-HPLC) with diode-array detector PDA 2996. Detection was carried out at the wavelength 205 nm. The average concentration of lactoferrin in goat milk was 120 ± 18 μg/ml. The lactoferrin content was increasing within the lactation period in the ranges of 98 ± 170 μg/ml in April to 149 ± 19 μg/ml in November. The heat treatment (pasteurisation at 72°C for 20 s) resulted in no significant effect on the lactoferrin content. No statistically significant differences ( P = 0.05) were found between the values of raw and pasteurised goat milk.

The aim of this study was to evaluate the composition of caseins in milk and dairy products employing a fast and effective method of reversed-phase high-performance liquid chromatography (RP-HPLC). An additional task was to separate and identify αS1- and αS2-caseins by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and thus confirm their presence in the analysed samples. A total of 120 milk samples (cows’, goats’ and ewes’) and 46 samples of dairy products (cheese, yoghurt) obtained from farms and milk bars in Czech Republic were analysed by RP-HPLC. All main casein components (αS1-, αS2-, β- and κ-casein) were identified and quantified. Statistically significant differences between individual caseins in various samples of milk and dairy products were detected. RP-HPLC profiling of samples showed that the presence of individual caseins depends primarily on the animal source of milk but also on the technological treatment of dairy products. The quantity of αS1-casein, which has the most pronounced allergenic potential, varied significantly between different samples. The current study demonstrated good performance of the novel approach for RP-HPLC analysis of αS1- and αS2-caseins utilizing in-house prepared analytical standards as well as provided valuable data regarding the casein profile of milk and dairy products on the market.

The main aim of this work was to determine the effect of high pasteurization of milk (85 degrees C/3 s) on the residues of tetracycline and oxytetracycline. The samples of raw cow's milk, purchased from a vending machine, were spiked with standard solutions of tetracycline and oxytetracycline. The content of the residues of tetracycline antibiotics was measured before and after heating. Pre-cleaned samples were extracted by a mixed-mode solid phase extraction technique and analysed using high performance liquid chromatography/diode array detection. Whereas the residues of tetracycline decreased only by 5.74% and were not significantly different (P > 0.05), the residues of oxytetracycline decreased by 15.3% and this distinction was highly significant (P <= 0.01). Based on the results of our study, the tetracycline antibiotics were proved to have differences in the thermostability of particular substances at pasteurisation temperatures.