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  • Author or Editor: L. Varga x
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The influence of a food-grade long-chain polyphosphate mixture on the growth and survival of spoilage micro-organisms during storage in an experimental processed cheese spread formulation was evaluated. The emulsifying salt was added to the cheese blend at a concentration of 0.5% or 1.0%. A control product was also manufactured, which contained monophosphate instead of polyphosphate as emulsifying salt, with all other ingredients being identical to those in the experimental processed cheese spread. Half of the finished products were subjected to accelerated shelf-life testing at 37 °C for 10 days, whereas the other half of them was stored refrigerated at 4 °C for 120 days. Microbiological analyses (enumeration of viable cell counts, mesophilic sulphite-reducing clostridia, coliforms, yeasts and moulds) and sensory tests were performed at regular intervals. The results showed that polyphosphates had a beneficial effect on the shelf-life of the processed cheese spread tested in that they significantly reduced (P<0.05) the growth or survival rates of spoilage bacteria, especially of mesophilic sulphite-reducing clostridia. Polyphosphates also beneficially influenced the sensory, including textural properties of the experimental processed cheese spread. All the samples containing less than 1% polyphosphate showed signs of butyric blowing significantly earlier (P<0.05), during both accelerated shelf-life tests and regular refrigerated storage, than did the products fortified with 1% polyphosphate. In conclusion, the suitability of the long-chain polyphosphate formulation tested for shelf life extension of processed cheese spreads was demonstrated.

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The purpose of this research was to monitor the changes during storage in survival of bifidobacteria in a soft-frozen ice cream supplemented with a yeast cell wall-based product claimed to contribute to the functioning of the immune system. An ice cream mix was prepared and pasteurised. After overnight aging at 4 °C, it was inoculated with Bifidobacterium animalis subsp. lactis Bb-12. Two batches of the mix were supplemented with a commercial Saccharomyces cerevisiae cell wall product at 2.0% and 4.0% (w/w), whereas a third batch was left unsupplemented and served as control. The final mixes were frozen, and the three products were stored at –13 °C for 7 days. The ice creams contained viable bifidobacteria cells at levels exceeding 106 CFU g–1 throughout the storage throughout the storage period. Although the yeast supplement decreased the loss of viability of bifidobacteria during frozen storage of ice creams, it imparted a slightly bitter off-flavour to the samples and it also negatively influenced the original white colour of the product, thereby necessitating further work to develop flavoured varieties of the Saccharomyces cell wall-containing synbiotic ice cream.

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The biochemical characteristics and antibiotic susceptibility of 12 Ornithobacterium rhinotracheale strains isolated from chickens and turkeys suffering from respiratory clinical signs and the survival of some isolates on egg-shell and within chicken eggs during hatching were examined. All O. rhinotracheale strains showed typical biochemical characteristics. Among the 16 drugs examined, penicillin G, ampicillin (MICs ranging from ≤ 0.06 μg/ml to 1 μg/ml), ceftazidim (with MICs from ≤ 0.06 μg/ml to 0.12 μg/ml), erythromycin, tylosin, tilmicosin (with some exceptions MICs ranged from ≤ 0.06 μg/ml to 1 μg/ml) and tiamulin (MICs varied from ≤ 0.06 μg/ml to 2 μg/ml) were the most effective. Lincomycin, oxytetracycline and enrofloxacin also gave good inhibitions, but with most strains in a higher concentration (MICs ranged in most cases from 2 μg/ml to 8 μg/ml). The other antibiotics inhibited the growth of O. rhinotracheale only in very high concentrations (colistin) or not at all (apramycin, spectinomycin, polymyxin B). At 37 °C, O. rhinotracheale did not survive on egg-shell for more than 24 hours, while upon inoculation into embryonated chicken eggs it killed embryos by the ninth day, and from the 14th day post-inoculation no O. rhinotracheale could be cultured from the eggs at all. These results suggest that O. rhinotracheale is not transmitted via eggs during hatching.

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We are synthetized thermo- and pH-sensitive gels, which are then tested as skin extenders. Our aim is the development of copolymer and composite hydrogels that, when implanted under the human skin, swell osmotically and thereby induce skin growth. During the polimerization reaction we are produced copolymers with varyable composition, which are proceed from two acrylic compounds [N- isopropyl- acrylamide (NIPAAm), and acrylamide (AAm)]. The mechanical strength and the swelling stability of the gels are enhanced by the addition of fillers [Na- montmorillonite (Na- m.) and with alkyl- ammonium ion organophilized Na- montmorillonites [(C n - m.), n = 4, 12, 18]. With this method we are synthetized composite- hydrogels. The filler content of composites varies between 1 and 25 wt%. We observed that in the case of composites synthesized with the addition of fillers, relatively low filler contents (1–5 wt%) resulted in more extensive swelling and stronger gel structure. In the course of the experiments the monomer composition of the gels (0/100–100/0 mol% NIPAAm/AAm) and in the case of composites, the quality (montmorillonite and organophilized montmorillonite) and quantity (1–25 wt%) of fillers are varied. The extent of swelling and the viscoelastic properties can be manipulated through the ratios of these parameters. In the case of certain copolymer and composite gels, values of desorption enthalpy (ΔH m ) corresponding to the actual water contents were also determined by thermoanalytical measurements (DSC). Swelling values determined by gravimetry and enthalpies calculated from DSC measurements were found to be in good correlation. Evaluation and comparison of the rheological and DSC results also allowed conclusions to be drawn concerning the types of interaction operating among the three components of the system, i.e. the polymer skeleton, the filler and water molecules. We found that water molecules within the gel matrix are bound to the 3-D polymer lattice with bonds of different strengths and the strength of these interactions are dependent on both hydrophilicity and charge conditions. In the case of hydrophobic NIPAAm composites a more extensive swelling can be achieved by applying montmorillonite fillers with hydrophobized surfaces, whereas in the case of hydrophilic AAm-based composites the use of hydrophilic montmorillonite fillers ensure more extensive swelling.

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Abstract  

The tetra-alkyl-ammonium halides are electrolytes that have special characteristics due to the presence of hydrocarbon chains. They have been used asmodel compounds to study hydrophobic interactions due to their fairly large solubility in water and because of the possibility of change in the length and geometry of the alkyl chains. In this work the solution enthalpies of tetra-n-butyl-ammonium bromide, tetra-sec-butyl ammonium bromide, tetra-iso-butyl-ammonium bromide and di-n-butyl-di-sec-butyl ammonium bromide were determined at 298.15 K at concentrations between 0.001 and 0.01 mol kg−1. The experimental method used was isoperibol calorimetry. The results were extrapolated fitting the experimental data by least squares to obtain the solution enthalpies at infinite dilution. The hydrocarbon chains studied were so chosen because the tetra-n-butyl-ammonium ion is considered to be a structure maker for water. The results show that the geometry of the ion and of the hydrocarbon chains play an important role in the behavior properties of the solutions.

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The importance of short food supply chains is increasing in the food sector, and direct selling is a promising alternative to commercial chains in dairy trade. Several channels and practices of direct raw milk sales exist in Hungary. Because short food supply chains in the Hungarian dairy sector have not yet been investigated in detail, we have little or no knowledge on the composition of directly sold raw milk. For this reason, a 9-month study was undertaken from June 2013 through February 2014, wherein directly sold raw bovine milk samples were tested for fat, protein, lactose, and solids-not-fat contents and for freezing point. A total of 21 direct sellers located in Budapest, Hungary were sampled twice a month. The results were compared to the official Hungarian raw milk quality data referring to the same period. The direct milk vendors involved in this study were found to sell raw milk with reduced levels of lactose and solids-not-fat and elevated freezing points, compared to the national raw milk data. The findings of this research underline the need for stricter regulations and control with respect to direct raw milk sales in the country.

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Abstract  

Positron annihilation (PA) investigations were performed on zeolites (X, Y and ZSM-5) and on microcrystalline MgO, Al2O3 and SiO2, providing long lifetime components attributed to o-Ps atoms. In addition to the positron lifetime (LT) measurement, the energy distribution (ED) of the annihilation gamma radiation spectrum was recorded in the 30 keV–1.5 MeV range for different samples and was compared to reference distributions for Si and GaAs samples, where no long-living Ps states are formed. Apart from the strong correlation with the water content in the samples, the positron data collected testify much more pronounced positronium hosting features for powders of the mentioned oxides than for zeolites. Positron LT spectroscopy combined with recording of the ED of the annihilation radiation provides reliable information on the formation of long living 3 states.

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In anticipation of a future vaccination program against rotavirus disease, a longitudinal survey has been set up to evaluate the epidemiologic features of rotavirus infections. In this report hospitalisation data and serotyping results are compiled from an epidemiologic survey conducted in Baranya County, Hungary. It was found that rotavirus-associated hospitalisation constituted a major part of infectious gastroenteritis cases (range, 14.9% to 28.5%). A higher proportion of rotavirus-positive cases was recorded when the serotype of predominant strains changed from G1 (1996-1999) to G4 (1999-2000), however, due to the short time period it was not possible to demonstrate a firm association between serotype prevalence and rotavirus-associated hospitalisation rate. In the future, such studies might help to understand if serotype-specific immunity against rotavirus infection plays an important role at the population level and if (re-)emerging rotavirus strains make an impact on the annual disease burden.

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In frames of a Hungarian Scientific Research Fund (OTKA) project (No. K49604), we systematically investigated all published surface geoelectric arrays, since a part of them are out of use, even completely forgotten. Even in case of these latter ones we were optimistic in their potential renaissance, due to the rapid advance in geophysical knowledge and technical development. Therefore at first we collected all surface geophysical arrays, ever used in geophysical exploration. We presented all of them in a standard way, and we classified them. This collection proved to be the basis of still on-going inter-comparisons. We revealed the original motivation of their design, as well. Then we produced parameter sensitivity maps for all possible arrays, by using a new analytical approach. Parameter sensitivity maps for non-linear and focussed arrays had never been presented before. Through examples (mainly for null-arrays, one of the focal points of our project) we presented, how these maps can be applied. Then another characterizing parameter, the depth of investigation was studied. The so-called depth of investigation characteristics (DIC) was computed for all the 30 arrays, where it exists, both in terms of Roy and Apparao (1971) and Edwards (1977). We carried out various comparisons, and revealed a complex relation among vertical resolution, depth of investigation and noise. We showed how the depth of investigation is constrained by the noise level. Therefore the maximal (theoretical) depths of investigation for 6 arrays were studied at various noise levels. Besides some further theoretical studies, our further work will concentrate on measurements. The general characterization of so many geoelectric arrays provides a better knowledge about them, and it will be hopefully useful also for other teams to select always the optimal arrays in their field problem. It should be mentioned, that this paper does not contain mathematical details. If the reader would like to reproduce the results demonstrated on the figures, the referred previous publications of the authors should be studied.

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