MFLP-44 Determination of Aerobic and Anaerobic Sporeformers
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A86882DCB6ED43FFA5726719BCA94E13 |
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文件大小(MB)： |
0.03 |
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页数： |
6 |
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日期： |
2012-3-2 |
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Published by: POLYSCIENCE PUBLICATIONS, P.O. Box 1606, Station St-Martin, Laval, Quebec,Canada H7V 3P9. TEL.: 1-800-840-5870. FAX: (450) 688-1930.,Government of Canada Gouvernement du Canada,Laboratory Procedure MFLP-44,April 1998,HEALTH PROTECTION BRANCH,OTTAWA,DETERMINATION OF AEROBIC AND ANAEROBIC SPOREFORMERS,John W. Austin,Microbiology Research Division,Bureau of Microbial Hazards,Food Directorate,Postal locator: 2204A2,Ottawa, Ontario K1A 0L2,1. APPLICATION,This method is applicable to the enumeration of viable sporeforming microorganisms in accordance with the,requirements of Sections 4 and 7 of the Food and Drugs Act. This revised methode replaces MFLP-44, dated,May 1988.,2. PRINCIPLE,This Aerobic Sporeformers count (ASF) and Anaerobic Sporeformers count (AASF) estimates the numbers of,viable sporeforming organisms per g or mL of product. A portion of the product is mixed with a specified agar,medium and incubated under specified conditions of time and temperature. It is assumed that each viable,microorganism will multiply under these specified conditions of incubation and give rise to a visible colony,which can be counted. This revised method replaces MFLP-44 dated May 1988.,3. DEFINITIONS OF TERMS,See Appendix A of Volume 3.,4. COLLECTION OF SAMPLES,See Appendix B of Volume 3.,5. MATERIALS AND SPECIAL EQUIPMENT,1) Refrigerator.,2) Trypticase soy agar.,3) Water bath adjustable to 45oC and 75oC.,4) Disinfectant.,5) 0.1% peptone water.,6) Blender.,MFLP-44,- 2 - April 1998,7) pH meter.,8) 1N NaOH.,9) 1N HCl.,10) Thermometer reading to 75oC.,11) Petri plates.,12) Incubator adjustable to 75oC.,13) Anaerobic jar.,14) Colony counter.,15) Tally register.,16) 0.1% 2,3,5 triphenyltetrazolium chloride.,17) "Standard methods for the examination of dairy products" A.P.H.A. 14th or latest Edition.,6. PROCEDURE,Analyze each sample unit individually.,The test shall be carried out in accordance with the following instructions:,6.1 Handling of Sample Units,6.1.1 In the laboratory prior to analysis, except for shelf-stable foods, keep sample units,refrigerated (0-5oC) or frozen depending on the nature of the product.,6.1.2 Analyze sample units as soon as possible after receipt in the laboratory.,6.2 Preparation of Media,6.2.1 Prepare trypticase soy agar and dispense in appropriate quantities. Sterilize.,6.2.2 Temper prepared melted agar in a water bath to 45oC ensuring that the water level is 1 cm,above the level of the medium in the bottles.,6.2.3 Clean surface of working area with a suitable disinfectant.,6.2.4 Mark clearly the duplicate Petri plates identifying sample, sample unit, dilution and date of,inoculation.,6.3 Preparation of Dilutions,6.3.1 Prepare sterile 0.1% peptone water diluent.,6.3.2 To ensure a truly representative analytical portion agitate liquid or free flowing materials until,the contents are homogeneous. If the sample unit is a solid, obtain the analytical unit by,taking a portion from several locations within the sample unit.,6.3.3 Prepare a 1:10 dilution of the food by aseptically adding 10 g or mL (the analytical unit) into,90 mL of the diluent. Blend or shake according to the type of food as indicated in Table I.,MFLP-44,- 3 - April 1998,6.3.3.1 If a homogeneous suspension is to be obtained by blending, the blending time should,not exceed 2.5 min in order to prevent over-heating.,With foods that tend to foam, use blender at low speed, and remove aliquot from below,liquid/foam interface.,6.3.3.2 If a homogeneous suspension is to be obtained by shaking, shake the dilution bottles,25 times through a 30 cm arc in approximately 7 sec.,6.3.3.3 In some instances it may be desirable to prepare the initial dilution on a percent basis,in order to obtain a more accurate weight of the material to be tested than is provided,for by the customarily employed dilution ration basis, i.e., a 10% solution,(suspension) is represented by 10 g (mL) per 100 g (mL) of solution (suspension),whereas a 1:10 dilution is based on 10 g (mL) of product (solute) plus 90 g (mL) of,diluent (solvent).,6.3.4 Check the pH of the food suspension. If the pH is outside the range of 5.5-7.6, adjust the pH,to 7.0 with sterile 1N NaOH or HCl.,6.3.5 For each analytical unit, pipette 20-25 mL of 10-1 dilution (using 0.1% Peptone Water, see,section 5.3) into a sterile tube. Also pipette 20-25 mL of a 10-1 dilution into an extra tube and,place a thermometer into that tube (Control tube).,6.3.6 Place the tubes into a water bath at 75oC. Shake the tubes intermittently until the,thermometer of the control tube reads 75oC; then hold for 20 minutes.,6.3.7 Prepare subsequent required dilutions from the heat-t……
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