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- Author or Editor: K. Szakmár x
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The spoilage of meat products (N>5×106 CFU g−1) can be delayed by cooling and low-temperature storage and transport. The highest extent of interruption in the cold chain occurs at the time of delivering the meat product to the individual’s home after purchasing it. Consumer behaviour and the ambient temperature largely influence the shelf life of products. In our research, we examined the buying habits of customers in Hungary. Based on these results, we carried out the cold chain interruption of vacuum-packed sliced ham (1, 2, 3 h) under laboratory conditions, at temperatures of 15, 25, and 35 °C. The microbial count was determined by a quick method based on redox-potential measurement in two-three days until the products were deteriorated. Our experiments resulted in the expected outcomes; however, we concluded that even average customer habits (1 h cold chain interruption) at higher temperature periods (T>20 °C) decrease the shelf life of ham by 6 days. We set up a mathematical model through which the changes of microbial counts can be determined as a function of product temperature changes, the period of delivery, and the subsequent period of cold storage. R2=0.9 correlation was given between predicted and measured microbial counts (logN).
The aim of this study was to develop simple, rapid and reliable methods for the selective determination of Bifidus essensis from ACTIVIA (Danone) yogurts. The methods are based on a modified MRS medium (B-broth), which does not contain inhibitory additives. The sugar source of the medium is maltose, which is metabolized by the bifidobacteria applied in the probiotic products, and not by the normal microflora of yogurt ( Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus ). The redox potential of the medium was reduced with cysteine-HCl. Due to its reduced redox potential, the new bouillon is suitable for aerobic cultivation of bifidobacteria, while in agar form it needs anaerobic incubation. In bouillon form (MPN method) the incubation time is only 2 days compared to the 5-day requirement of the classical anaerobic plate counting methods. The B-broth in diluted form was successfully used in a RABIT (Don Whitley) equipment for selective impedimetric determination of bifidobacteria in Danone yogurts. The exact detection time of the Bifidobacterium counts in a good quality probiotic yogurt, containing bifidobacteria at a concentration of 10 7 to 10 8 CFU ml −1 is not more than 10 to 12 h (in contrast to the 5 days of classical anaerobic plate counting methods).
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.
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.
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.