The Study Of Rapid Detection Techniques Of Food-borne Pathogens Based On The Metabolites

Contamination caused by food-borne pathogens was the main reason that resulted in food-borne diseases. It was one of the important measures to guatantee human’s health and economy free of loss that detected and identified food-borne pathogens rapidly and accurately, then prevented and controlled infectioin caused by them. Total bacterial account, Escherichia coli and Salmonella were specified test items of microbial limit in national standard of pasteurized milk. It was of great importance to detect these three microbial items rapidly to guarantee the quality of milk and safty of milk driking. Piezoelectric sensor was rapid response, high sensitivity, low cost and user-frendly control. For these accounts, it had extensive prospects in the rapid detection field of pathogens. This topic studied new piezoelectric techniques and methods applied to rapid detection and identification of food-borne pathogens through which analysed metabolic characteristics of food-borne pathogens in fresh milk. The main researches were as followed.(1) Studied the method of analysing fresh milk contaminated by Escherichia coli based on HS-SPME/GC-MS. Fiber of SPME choosed was75urn CAR/PDMS. Chromatographic column was Rtx-5. The temperature program were that30degree Centigrade was kept12minutes, and rised to102degree Centigrade4degree Centigrade per minute, then rised to170degree Centigrade2.5degree Centigrade per minute, then rised to220degree Centigrade10degree Centigrade per minute, totally70.2minutes. Based on the above method, results indicated that there were19main detected volatile metabolites of fresh milk contaminated by Escherichia coli, including amines, acids, ketones, ethers, aldehydes and alkanes. There were17main detected volatile metabolites of fresh milk, including amines, acids, ketones, ethers, aldehydes and alkanes. Comprehensive analysis shew that the typical volatile metabolites of fresh milk contaminated by Escherichia coli were2-hydroxy-acrylic amide, propylene ammonia acyl-acrylic amide,3,6-dimethyl-2,5-piperazine diketone, cathinone, octanal. The establishment of this method could provide theoretical foundation and technical support for identification of contamination caused by food-borne pathogens based on volatile metabolites. (2) Studied frequency shift detection (Microorganisms Detection Time, MDT) method to detect total bacterial account of fresh milk based on piezoelectric sensor. We obtained the typical response curve of microorganisms in fresh milk based on piezoelectric sensor’s sensitive response of milk electrical parameter change caused by microorganic metabolites. Defined microorganism detection time (MDT) based on the typical response curve. The relationship between the logarithm of initial concentrations of bacteria and MDT was established. There was a linear relationship between the logarithm of initial concentrations of bacteria and MDT in the intial concentration of about10～106cfu/mL,1gC=7.21602-0.43219MDT (R2=0.9632). The detection limit was101cfu/mL. We detected the number of bacteria of different batches of fresh milk using MDT method, meanwhile, comparing with national standard method. It turned out that the established method was accurate, rapid and simple, which could provide technical support for rapid detection of total bacterial account in microbiological lab.(3) Studied MDT methods to detect Escherichia coli, Salmonella enterica in fresh milk rapidly based on piezoelectric sensor. First, we obtained the typical response curves of Escherichia coli, Salmonella enterica of different initial concentrations in detecting culture medium. Then, we entablished the standard equations between intial concentrations of Escherichia coli (N1), Salmonella enterica (N2) and MDT,1gN1=7.17613-0.72905MDT (R2=0.9875),1gN2=7.66972-0.72077MDT (R2=0.9822). In the end, we applied the established method to detect fresh milk contaminated by different concentrations of Escherichia coli, Salmonella entericai, meanwhile, controlled by the plate count method validation. The results shew that MDT method could detect fresh milk contaminated by103～107cfu/mL Escherichia coli within6.08hours and fresh milk contaminated by102～107cfu/mL Salmonella enterica within9.09hours. The method provided train of thought for simple and rapid detection of food-borne pathogens based on piezoelectric sensor.