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The standard culture methods in food hygiene used for the determination of microbial count are slow. In order to shorten the duration of detection of sampled bacteria, the Authors elaborated a redox potential measurement-based new method. The applicability of the new method was compared to the standard swab method in the framework of interlaboratory proficiency test aimed to determine the microbial contamination of model surfaces and in the hygienic control of a food manufacturing pilot plant. The comparative evaluation of total counts and Enterobacterium counts obtained by standard plate pouring and by the new method proved that there is no significant difference between the results of the two procedures. The total count determination with the new method lasted only 10–16 h in contrast to 72 h of plate counting. Particular advantages of the new method are that the bacterial count of the swab can be determined directly, without any washing down of the microbes from the swab and due to the different shapes of the redox curves, the total count and enterobacteria could be enumerated simultaneously from the same nonselective nutrient broth.

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The aim of this study was to investigate the occurrence of Salmonella enterica and its most important serovars Salmonella Infantis, Salmonella Enteritidis, Salmonella Typhimurium, and Campylobacter spp. in the broiler meat production chain. Altogether 110 pooled samples were analysed; environment, cloaca, body surface at the farm, then carcass, offal, and packed meat from the slaughterhouse. The combination of redox potential measurement and realtime PCR was used for the detection of the microbes.

At the farm, the first Salmonella positive result came from the water system, then it appeared in most of the samples. In contrast to the absence of Salmonella on the birds’ body surface before transportation, by the end of the processing it had reached 100%, with the only identifiable serovar being S. Infantis (65%). All packed meat samples showed positivity, from which 70% was S. Infantis.

Campylobacter appeared at the farm on the 3rd week and remained significant during the breeding. After the slaughtering process, the contamination was 100% in the carcass, offal, and packaged meat samples.

Our results demonstrated the success of the Salmonella control program, by the low prevalence of S. Typhimurium and Enteritidis.

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A selective synthetic solid minimal medium (BS agar) was developed to detect antimicrobial drug-residues in foodstuffs using Bacillus subtilis indicator culture. This medium contains an ammonium salt as nitrogen source and either glucose or sodium pyruvate as carbon sources.Its selectivity is based on the fact that Bacillus subtilis is still able to grow if the minimal medium consists of simple inorganic substances as nitrogen sources, and glucose or pyruvate as carbon supply. Using these new synthetic media for microbiological assays assessing certain antimicrobials, the diameter of the inhibition zones were 1.4–4 times wider than on the Mueller-Hinton agar.The advantages of the BS agars are their standard compositions, the absence of inhibitors, the reproducible quality and the low costs.

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Acta Alimentaria
O. Erdősi
K. Szakmár
O. Reichart
Zs. Szili
N. László
Z. Balogh
P. Székely Körmöczy
, and
P. Laczay

The classical ISO (2002) standard as reference method and the combination of redox potential measurement with real-time PCR technique were applied to detect Salmonella in milk, egg, broiler meat, and artificially contaminated egg samples. Food samples of 25 g were homogenized in 225 ml of RVS broth to prepare the basic suspension of the comparative tests. In the combined method the redox potential measurement technique serves as the selective enrichment system of the real-time PCR equipment. The reliable screening of Salmonella-free, negative samples by the redox potential measurement technique needed only 24 h. These negative samples determined by the PCR and the classical standard method in all cases proved to be negative as well. In case of positive redox result the Salmonella from the enriched suspension of the redox test-cell was identified by real-time PCR in 3 hours, instead of the conventional biochemical identification. Comparing our protocol to the ISO (2002) standard method, the total detection time of Salmonella presence/absence was less than 24 h contrary to the 114 h of the conventional method.

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