Rapid detection of Salmonella in food by redox-potential measurement based method combined with real-time PCR

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

Application of the redox potential measurementbased rapid method in the microbial hygienic control

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