Studies On Bacteria Flow Cytometry Measurement Method And Foodborne Pathogenic Bacteria Reference Material Preparation Technology

In recent years,food safety problems caused by food-borne pathogens were taking place all across the world.Therefore,it was necessray to do research on inspection method and matrix reference material preparation of food-borne pathogens.1.Microorganism detection was carried out to do fast measurement on Staphylococcus aureus using flow cytometry method(FCM)which was a modern microbial detection method.Food-borne Staphylococcus aureus was determinated by optimizing the parameters of flow cytometry machine.Meanwhile,the control test was also carried out with the plate count method.The replicated results showed:the results tested by flow cytometry machine was 1.24×106 CFU/mL,plate count machine was 2.87×105 CFU/mL,respectively.It also showed the two detection method had a good correlation(R2= 0.9995)by weighing the different ratio of the volume of live and dead bacteria.2.Staphylococcus aureus reference material was prepared by freeze drying method.The results showed:protection rate of the composite protective agent by freeze drying method reached 51.74%;The concentration of Staphylococcus aureus reference material prepared in this work was kept at(13259±868)CFU/mL after three weeks’ decay.There was no significant difference after testing random 15 bottles of Staphylococcus aureus reference material,the values of variance was 1.42.The number of live bacteria of Staphylococcus aureus reference material prepared in this work could be stable for 180 days at the temperature blow-20℃.3.Escherichia coli reference material was prepared using freeze-drying method.The limited amount was meet with the requirements of "National food safety reference Milk Power"(GB19644-2010).The results showed:the protection rate of the composite protective agent on Escherichia coli reached 53.19%;The concentration 1 of Escherichia coli reference material prepared in this work was stablished at(101± 12)CFU/mL,the concentration 2 was stablished at(50±11)CFU/mL.There was no significant difference after testing random 11 bottles of Escherichia coli reference material,the values of variance was 0.93 and 0.41 respectively.The number of live bacteria of Escherichia coli reference material prepared in this work could be stable for 180 days at the temperature blow-20℃.