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An immunoreaction-based method was investigated for the detection of aflatoxin M1 (AFM1), which is the hydroxylated metabolite of aflatoxin B1 (AFB1). This mycotoxin may be found in milk and milk products obtained from livestock that have ingested contaminated feed. Quantitative analysis of AFM1 was carried out using indirect (competitive) immunoassay method, which can be used for low weight molecules. The real-time measurement was done with Optical Waveguide Lightmode Spectroscopy (OWLS) technique. After the optimization of the chemical and biochemical parameters (determination of the optimal concentration of the immobilized AFM1-protein conjugate, determination of the AFM1 antibody content of the samples, etc.) real samples were also examined. Three kinds of milk sample preparation methods (filtration, centrifugation, size exclusion centrifugation) and two dilution rates (100 and 200 fold) were compared. The presented competitive immunoassay method showed the best results when 100 fold diluted filtered or centrifuged milk samples were examined. The dynamic measuring ranges for AFM1 were 0.001–0.1 ng ml−1 and 0.0005–0.01 ng ml−1, respectively.

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An amperometric biosensor for the detection of organophosphorus and carbamate type pesticides was developed. Acetylcholinesterase enzyme (electric eel) was immobilized in a thin-layer enzyme cell, and acetylthiocholine chloride (AcTCh) was used as substrate. Amperometric detection with glassy carbon electrode was performed in a stopped-flow FIA system. The inhibition effect of dichlorvos (DDVP), carbofuran, methomyl, and pirimicarb were examined: the linear measuring ranges were 0.001–0.1 μmol l−1, 0.001–0.1 μmol l−1, 0.2-1 μmol l−1, and 0.1–10 μmol l−1, respectively. Soil extract and apple juice were measured with spiking method. It was concluded that the biosensor can be used for screening pesticide residues in food and environmental samples.

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Acta Alimentaria
Authors:
N. Adányi
,
É. Gelencsér
, and
I. Bata-Vidács
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Acta Alimentaria
Authors:
L. Szalóki-Dorkó
,
A. Nagy
,
N. Adányi
, and
R. Tömösközi-Farkas
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Acta Alimentaria
Authors:
É. Kónya
,
G. Bujdosó
,
M. Berki
,
M. Nagy-Gasztonyi
, and
N. Adányi

Two Hungarian and two introduced walnut cultivars were examined as fresh samples and under storage. Some important compositional data were determined in order to evaluate the differences between the cultivars and the changes after storage. The cultivars’ oil contents were the same, but there was some difference in fatty acid composition; ‘Alsószentiváni 117’ had a higher mono-unsaturated fatty acid content than the others. Considering the oxidative stability, ‘Alsószentiváni 117’ contained good properties in all stages (induction time equals or higher than 10 h). Lower antioxidant capacity was measured in ‘Chandler’ samples compared to the others. ‘Alsószentiváni 117’ has higher α- and γ-tocopherol contents than the other cultivars studied. Two different drying methods were also compared in case of the Hungarian cultivars. The changes in compositional data showed no tendencies. We found that Hungarian cultivars were at least as valuable as the introduced ones.

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To explore new possibilities of enzyme immobilization, we investigated bioactive layers prepared by a new procedure based on three-phase partitioning (TPP) of proteins. By this method a third phase or midlayer as a protein layer can be developed at the interface of a protein system containing two phases (organic solvent/aqueous salt solution). Proteins of meat origin partitioned together with bioselective material (e.g. an enzyme) after centrifugation resulted in excellent bioactive layers.In the newly developed sensor, glucose oxidase was immobilized in a layer, which was fixed on the surface of a platinum ring electrode. The biosensor was built in a flow injection analyzer (FIA) system, where the hydrogen peroxide generated during the enzymatic reactions was determined by an amperometric cell. The parameters for biochemical and electrochemical reactions (ion concentration and pH of buffer, flow rate) were optimized. The linear range of analysis by the newly developed sensor was from 0.5 to 10 mmol l–1 glucose. The biosensor could be used for more than 300 analysis.

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Acta Alimentaria
Authors:
G. BujdosÓ
,
M. Tóth-Markus
,
H. Daood
,
N. Adányi
, and
P. Szentiványi

Eight registered Hungarian walnut cultivars were tested for composition and sensory properties. The samples were collected at the Experimental Fields of the Research Institute for Fruitgrowing and Ornamentals in Érd-Elvira major. Proximate composition, fatty acids, minerals (P, Na, Ca, Mg, Ca, Fe and Se), polyphenols and vitamins (C, E) were determined in four consecutive years 2003–2006. The tested cultivars have an oil content, which falls within the upper range of the literature values. Polyphenols, iron and selenium contents are also high while the values for potassium and phosphorus are in the lower part of the given range. In our case, the crop years make a larger difference in the composition than the cultivars. Tiszacsécsi 83 is the only cultivar slightly differing from the others in lower mineral and protein content.

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Acta Alimentaria
Authors:
N. Adányi
,
L. Szalóki-Dorkó
,
R. Tömösközi-Farkas
,
A. Nagy
, and
É. Kónya
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Acta Alimentaria
Authors:
Kerti K. Badakné
,
L. Szalóki-Dorkó
,
Zs. Zalán
,
N. Adányi
, and
K. Takács
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