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1. Principle&application scope

E.coli and coliform which exist in intestinal and feces of animal can cause water pollution and food poisoning. E.coli&coliform count plate which consist of selective medium, soluble bibulous gel, galactosidase, and glucuronidase could test E.coli and coliform at the same time. E.coli show blue color while other coliform show red color after growing on the count plate. This product is suitable to detect total coliform number in food material such as milk drinks and condiment, hygiene detection of instrument surface.

Executive standard : Food sanitary microbiology testing coliform-Petrifilm TM count plate method( GB/T 4789.38)

2.  Using method

2.1 Sample preparation: Prepare the 1:10 solution by placing 25g or 25mL sample into 225mL sterile phosphate buffer solution or sterile saline, then, prepare 1:100 solution by suck 1mL solution(1:10) into 9mL sterile saline, and so on to prepare tenfold increasing serial solution if necessary.

2.2 Inoculation: Select 1 or 2 dilute solution to do the test for ordinary sampel ,while for liquid sample which has little coliform directly suck the raw liquid to do the test. Place the E.coli&coliform count plate onto sterile experiment table, uncover the film on the surface. Suck 1mL solution with sterile pipette , and then drop it slowly and evenly onto the count plate. Then cover the film gently and stand it for 10s to let the medium solidify. Inoculate two count plates for each diluted sample solution. At the same time do a blank control.

2.3 Culture: Superimpose the count plates together and place them back to ziplock bags, and seal them well. And then put them in the incubator of 36℃±1℃for 15-24 hours with the transparent side up. The quantity of superimposed count plates should not be more than 12.

3. Results:

E.coli shows blue color while other coliform shows red color after growing on the count plates.

4. Counting method

4.1 Select the plates of which the quantity of coliform is between 15CFU and 150CFU.

4.2 If the coliform quantity of coliform on two serial different dilution ratio count plates is both between 15CFU and 150CFU, multiply the average coliform quantity on them by dilution multiple as result data.

4.3 If the coliform quantity of coliform on all the dilute ratio count plates is less than 15, multiply the coliform quantity of coliform on minimum dilution multiple count plates by minimum dilution multiple as result data.

4.4 If the coliform quantity of coliform on all dilution ratio count plates is more than 150, multiply the coliform quantity on maximum dilution multiple count plates  by maximum dilution multiple as result data. Or convert the coliform quantity in one or two representative square on the count plate to the coliform quantity in each square, and then multiply the coliform quantity in each square by 20 as result data. 

Use CFU/mL or CFU/g as report unit.

5. Additional explanatory note

5.1 The PH of sample solution should be between 6.5 and 7.5, the solution should be adjusted with 1 mol/L NAOH or 1mol/L HCL.

5.2 Coliform is usually Chinese food hygienic detection index, while in Europe, E.coli is the food hygienic detection index. Therefore, this product has wide application prospects in area of export food and aviation food.

6. Preservation condition

This kind of product should be placed in the fridge of 4℃-10℃, and the expiration time is one year. Once the package is opened, those unused count plates should be placed back to the package and seal  well. Then place them in the fridge and exhaust them within one month. Condensate water may occur in high humid environment , it is better to warm the package to room temperature before unfolding it .