Determination of Escherichia coli in raw and pasteurized milk using a piezoelectric gas sensor array

The importance of assessing the microbiological safety of food products is beyond doubt, which is also true for milk and dairy products. They are very important in the diet and contain nutrients necessary for the human body in well-balanced proportions and in an easily digestible form. Therefore, the goal of this work was to evaluate the changes in the composition of the gas phase over milk based on signals from chemical sensors to predict the quantity of the coliform bacteria group in the milk samples. The gas phase over raw milk samples and samples after pasteurization, as well as for a standard (a model aqua solution of macronutrients and minerals), was studied using an array of sensors with polycomposite coatings, including those contaminated with E. coli bacteria. Assessment of microbiological indicators was carried out according to GOST in parallel with the gas-phase analysis. The patterns of the sensor signals, the calculation parameters, and calibration graphs with an error of ±100 CFU/ml were established based on the results of analyzing the standard samples. The adequacy of the calibration graphs was tested on seven raw milk samples, including those containing other types of pathogenic microorganisms (Staphylococcus aureus, Klebsiella spp., etc.). Thus, the proposed approaches to quantitative assessments of coliform bacteria in raw and pasteurized milk using gas-phase analysis with an array of sensors make it possible to significantly reduce the analysis time to 2-3 hours (including the sample collection and data processing) and thereby intensify the production of safe dairy products.