Csilla Mohácsi-Farkas

Mathematical modelling of the combined effect of water activity, pH and redox potential on the heat destruction.

Heat destruction of seven foodborne microorganisms (Lactobacillus plantarum, Lactobacillus brevis, Saccharomyces cerevisiae, Zygosaccharomyces bailii, Yarrowia lipolytica, Paecilomyces varioti and Neosartoria fischeri) as a function of the temperature, pH, redox potential and water activity was studied in synthetic heating media. Several mathematical models were developed for describing the heat destruction rate, most of them resulted in a good correlation between the fitted and measured values. The determination coefficients of the model-fitting were the best in case of lactobacilli and moulds (0.96-0.99) and the worst in case of the yeasts (0.81-0.88).

Fusarium mycotoxins in cereals harvested from Hungarian fields

ABSTRACT The Fusarium mycotoxins deoxynivalenol (DON), zearalenone (ZEN) and T-2 frequently contaminate grain crops in Middle and Eastern Europe. In this survey, 116 cereal samples (maize, wheat, barley and oat) were examined for DON, ZEN and T-2 mycotoxins. Samples were collected from different areas in two Hungarian regions (North and South Transdanubia). The method of analysis was indirect competitive ELISA. Maize was the most contaminated grain regarding DON (86%), ZEN (41%) and T-2 (55%) toxins. The average results of the deoxynivalenol and zearalenone tests of maize proved to be significantly higher than those of barley or oat. DON was the most represented Fusarium mycotoxin followed by T-2 and ZEN. The examination of these mycotoxins would be necessary at a larger scale as to re-evaluate permissible levels, so increase of the monitoring programme would be advisable for the future.

Radiolysis of sulfonamide antibiotics in aqueous solution: Degradation efficiency and assessment of antibacterial activity, toxicity and biodegradability of products

Numerous studies have been published on the radiolysis of sulfonamide antibiotic solutions but little effort has been made to monitor the biological properties of degradation products. A complex approach should also clarify the changes in antibacterial activity and biodegradability, besides the usual screening of toxicity. To fill this gap, the ionizing radiation induced degradation of four sulfonamide antibiotics was investigated in dilute aqueous solutions, with emphasis on the biological assessment of decomposition products. Complete removal of sulfonamides was achieved by a low absorbed dose (1.5kGy). 2-2.5kGy dose was needed to transform the persistent initial molecules to substances biodegradable in both river water and activated sludge. The ratio of the biological and chemical oxygen demand increased from <0.21 to at least 0.59, but values as high as 0.80 were also measured. It was demonstrated that antibacterial activity is due to the initial molecules, as it disappeared when the sulfamethoxazole concentration decreased below the minimal inhibitory concentration (30 μM). This means that the products have no antibacterial activity. Toxicity testing performed on test organisms from three different trophic levels and activated sludge evidenced that the toxicity depends both on the test organism and on the sulfonamide used. The degradation of initial molecules is not always enough to eliminate the environmental risk due to the toxic products formed e.g. inhibitory effects to Vibrio fischeri increased by 34% at 2.5kGy. For this reason, complex biological assessment of treated solutions has to play an important role in development and optimization of advanced treatment techniques.

Deoxynivalenol in wheat, maize, wheat flour and pasta: surveys in Hungary in 2008–2015

ABSTRACT Among Fusarium mycotoxins, deoxynivalenol (DON) is the most common contaminant in case of cereals and cereal-based foods in Hungary. In this study, Hungarian wheat (n = 305), maize (n = 108), wheat flour (n = 179) and pasta (n = 226) samples were analysed (N = 818). The samples were collected during 2008–2015 in Hungary. Applied methods of analysis were enzyme-linked immunosorbent assay and liquid-chromatography coupled with a mass spectrometer. Results were compared and evaluated with Hungarian weather data. Among cereal samples, in 2011, wheat was contaminated with DON (overall average ± standard deviation was 2159 ± 2818 µg kg−1), which was above the maximum limit (ML). In case of wheat flour and pasta, no average values above ML were found during 2008–2015, but higher DON contamination could be observed in 2011 as well (wheat flour: 537 ± 573 µg kg−1; pasta: 511 ± 175 µg kg−1).

Deoxynivalenol, zearalenone and T-2 in grain based swine feed in Hungary

ABSTRACT Fusarium genera can produce trichothecenes like deoxynivalenol (DON), zearalenone (ZEN) and T-2 toxin, which can occur in feed cereal grains. Enzyme-linked immunosorbent assays (ELISA) tests of different Hungarian swine feedstuff proved that these mycotoxins were present. In this survey, 45 feed samples from 3 significant Hungarian swine feedstuff manufacturers were tested. ELISA methodology validation showed mean recovery rates in ranges from 85.3% to 98.1%, with intermediate precision of 86.9-96.9% and variation coefficients of 3.4–5.7% and 5.9–7.1%, respectively. The results showed that among Fusarium toxins, generally DON was present in the highest concentration, followed by T-2 and finally ZEN in all tested swine feeds. Each of the mycotoxins was found above the limit of detection in all swine feedstuffs. Boars feed’s DON (average ± standard deviation was 872 ± 139 µg kg−1) and ZEN (172 ± 18 µg kg−1) results of one of the manufacturers were above the guidance values. It indicates the necessity for efficient monitoring of DON, ZEN and T-2 mycotoxins in swine feeds.

Influence of ionizing radiation on the antimicrobial activity of the antibiotics sulfamethoxazole and trimethoprim

ABSTRACT The response of the antimicrobial compounds sulfamethoxazole (SMX) and trimethoprim (TMP) – individually and in mixtures – to ionizing radiation was investigated using laboratory prepared mixtures and a commercial pharmaceutical formulation. The residual antibacterial activity of the solutions was monitored using Staphylococcus aureus and Escherichia coli test strains. Based on antibacterial activity, SMX was more susceptible to ionizing radiation as compared to TMP. The antibacterial activity of SMX and TMP was completely eliminated at 0.2 kGy and 0.8 kGy, respectively. However, when SMX and TMP were in a mixture, the dose required to eliminate the antibacterial activity was 10 kGy, implying a synergistic antibacterial activity when these are present in mixtures. Only when the antibiotic concentration was below the Minimum Inhibitory Concentration of TMP (i.e., 2 µmol dm–3) did the antibacterial activity of the SMX and TMP mixture disappear. These results imply that the synergistic antimicrobial activity of antimicrobial compounds in pharmaceutical waste streams is a strong possibility. Therefore, antimicrobial activity assays should be included when evaluating the use of ionizing radiation technology for the remediation of pharmaceutical or municipal waste streams.