MFHPB-35 Enumeration of Coliforms in Food Products and Food Ingredients Using 3MTM PetrifilmTM Coliform Count Plates
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D48E49BCC4CE41B699C04EBFEA34AC2C |
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0.02 |
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5 |
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日期： |
2024-7-30 |
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Published on the Food Directorate’s (Health Canada's) website at http://www.hc-sc.gc.ca/food-aliment.,Government of Canada Gouvernement du Canada,HPB Method MFHPB-35,February 2001,HEALTH PRODUCTS AND FOOD BRANCH,OTTAWA,ENUMERATION OF COLIFORMS,IN FOOD PRODUCTS AND FOOD INGREDIENTS,USING 3MTM PETRIFILMTM COLIFORM COUNT PLATES,Don Warburton,Evaluation Division, Bureau of Microbial Hazards,Food Directorate, HPB,Postal Locator: 2204A1,Ottawa, Ontario, K1A OL2,Don_Warburton@hc-sc.gc.ca,1. APPLICATION,This method is applicable for the enumeration of coliforms in food products and food ingredients.,This method may also be used for environmental sampling (see Laboratory Procedure,MFLP-41A and MFLP-41B). This revised method replaces MFHPB-34, dated April 1997.,2. PRINCIPLE,Petrifilm plates are a ready-to-use product developed by the 3M Company, St. Paul, MN. Media,are coated onto films, so that traditional media preparation is unnecessary, and both labour and,time savings are realized. Coliforms can be enumerated on the Petrifilm Coliform Count (CC),plates. The method uses bacterial culture plates containing dry medium and a,cold-water-soluble gelling agent. One mL samples are added directly to the plates. Pressure,when applied to the plastic spreader placed on the overlay film, spreads the sample over 20,cm2. The gelling agent is allowed to solidify, and the plates are then incubated and counted.,Validation and collaborative studies have found the Petrifilm CC method to be not significantly,different from the traditional methods (7.1 - 7.13, 7.15, 7.16).,3. DEFINITION OF TERMS,3.1 See Apendix A of Volume 2.,3.2 Petrifilm CC plates contain modified Violet Red Bile (VRB) nutrients; a,cold-water-soluble gelling agent; and 2, 3, 5-triphenyl tetrazolium chloride (TTC),indicator.,3.3 Coliforms produce gas from the fermentation of lactose in the medium. The gas is,trapped by the films and appears as a small bubble(s) associated with a red colony on,the Petrifilm CC plate.,MFHPB-35,- 2 - February 2001,3.4 Plastic spreading devices are provided with the Petrifilm plates. The smooth flat side is,designed to spread the sample over the growth area.,4. COLLECTION OF SAMPLES,See Appendix B of Volume 2.,5. MATERIALS AND SPECIAL EQUIPMENT,1) Petrifilm CC plates 6410/6416 (3M Canada Inc., PO Box 5757, London, ON, N6A 4T1),A.. Petrifilm CC plates. Store at or below 8 EC,B. Plastic spreading device,C. Package insert, including instructions for use. "Interpretation Guide," available,upon request,2) Appropriate diluents: Butterfield's phosphate buffer (7.12), IDF phosphate buffer (7.14),peptone salt diluent (ISO method 6887), buffered peptone water (ISO method 6579),0.85 - 0.9% saline, 0.1 % peptone water, and distilled water. If citrate buffer is indicated,in the standard, substitute warmed (40E - 45 EC) Butterfield's phosphate buffer,Note: Do not use citrate buffer or sodium thiosulfate with the Petrifilm method.,3) Stomacher, blender or equivalent,4) Incubator capable of maintaining 32 or 35EC,NOTE: It is the responsibility of each laboratory to ensure that the temperature of the incubators,or water baths are maintained at the recommended temperatures. Where 35EC is,recommended in the text of the method, the incubator may be at 35 +/-1.0E C. Similarly,lower temperatures of 30 or 25°C may be +/- 1.0EC. However, where higher,temperatures are recommended, such as 43 or 45.5EC, it is imperative that the,incubators or water baths be maintained within 0.5EC due to potential lethality of higher,temperatures on the microorganism being isolated.,5) pH meter or paper capable of distinguishing 0.3 to 0.5 pH units within a range of 6.0 to,7.5,6) 1N NaOH,7) colony counter and/or magnified illuminator,6. PROCEDURE,Carry out the test in accordance with the following instructions:,6.1 Handling of Food Sample,6.1.1 Prior to analysis, except for shelf-stable foods, keep sample refrigerated (2-8,EC) or frozen, depending on the nature of the product. Thaw frozen samples in a,refrigerator or under time and temperature conditions which prevent microbial,growth or death.,6.1.2 Analyze samples as soon as possible after their receipt in the laboratory.,MFHPB-35,- 3 - February 2001,6.2 Preparation for Analysis,6.2.1 Have sterile diluent ready. Disinfect the surface of the work area.,6.2.2 Place the Petrifilm plate on a flat surface. Mark identifying sample information on,film.,6.3 Preparation of Sample,6.3.1 To ensure a representative analytical unit, agitate liquids until the contents are,homogeneous. If the food sample is a solid, take representative portions from,several locations within the sample. Prepare a 1:10 dilutio……
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