MFHPB-22 Enumeration of Yeasts and Molds in Foods
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ID： |
4E0F8EA4773E4FC987CCCA6B13E7D9E5 |
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文件大小(MB)： |
0.1 |
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页数： |
9 |
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日期： |
2012-3-2 |
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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-22,January 2004,HEALTH PRODUCTS AND FOOD BRANCH,OTTAWA,ENUMERATION OF YEASTS AND MOULDS IN FOODS,Donna Douey,Calgary Laboratory,Canadian Food Inspection Agency,3650 36 St. N.W.,Calgary, AB T2L 2L1,doueyd@inspection.gc.ca,Patti Wilson,Dartmouth Laboratory,Canadian Food Inspection Agency,P.O. Box 1060,Dartmouth, NS B2Y 3Z7,wilsonpa@inspection.gc.ca,Evaluation Division,Bureau of Microbial Hazards,Food Directorate, Health Canada,Postal locator: 2204A1,Ottawa, Ontario K1A 0L2,1. APPLICATION,This method is applicable to the enumeration of viable yeasts and moulds in foods and food ingredients to,determine compliance with the requirements of Sections 4 and 7 of the Food and Drugs Act. This revised,method replaces MFHPB-22, dated March 2002.,2. PRINCIPLE,In the past, acidified media were used to enumerate yeasts and moulds in foods. Such media are now,recognized as inferior to antibiotic supplemented media that are formulated to suppress bacterial colony,development, enhance resuscitation of injured fungi, and minimize precipitation of food particles.,A medium, containing adequate nutrients for growth of most yeasts and moulds and antibiotics for inhibition,of most bacteria, is inoculated with a given quantity of the product. It is incubated at 22 to 25/C for 3 to 5 days.,Colonies appearing on the medium are then counted and/or examined. The method described here is a,"general purpose" method and may not be suitable for detection of yeasts and moulds adapted to certain,foods, e.g., foods of low water activity.,3. DEFINITION OF TERMS,3.1 See Appendix A of Volume 2.,3.2 Xerophiles: Moulds preferring reduced water activity for growth.,2 MFHPB-22,January 2004,3.3 Osmophiles: Yeasts preferring reduced water activity for growth.,PRECAUTIONS,Some yeasts and moulds can be infectious or can cause allergic responses, therefore, it is important to be,cautious when working with fungi. Ideally, plates should be held in incubators, not in an open room. Plate,lids should generally only be removed for things such as the preparation of a slide for microscopic,examination. Flamed needles should be cooled before making transfers to avoid dispersal of conidia and,other cells. Avoid inhalation of spores and other fungal products such as volatiles (do not smell).,4. COLLECTION OF SAMPLES,See Appendix B of Volume 2.,5. MATERIALS AND SPECIAL EQUIPMENT,The following media and media bases (1-5) are commercially available and are to be prepared and sterilized,according to the manufacturer's instructions. See also Appendix G of Volume 2 and reference 7.2 for the,formula of individual media.,NOTE: Media chosen for enumeration of xerophiles or osmophiles should, ideally, reflect the,characteristics of the food to be analyzed. Glucose, sucrose or glycerol supplemented agars,and diluents should be used for analysis of high-sugar products, while for high-salt foods, the,use of media containing sodium chloride, perhaps in combination with a sugar, is more suitable.,If the analyst uses any variation of the media listed here or any other media described,elsewhere for the food to be tested (either commercially available or made from scratch), it is,the responsibility of the analyst or Laboratory Supervisor to ensure equivalency.,General Purpose Agars and Diluents,1) Dichloran rose bengal chloramphenicol agar (DRBC),2) Plate count agar with chloramphenicol (PCA-C),3) Potato dextrose agar with chloramphenicol (PDA-C),4) Potato dextrose salt agar with chloramphenicol (PDSA-C) (for analysis of 'spreader' moulds),5) Dicloran-Glycerol Agar (DG18) (for xerophilic moulds),6) Malt extract agar containing 50%(w/w) sucrose (for high sugar foods such as honey),7) Peptone water, 0.1% (PW),8) Peptone water (0.1%) with 20% sucrose (W/V) - diluent for high sugar foods, such as honey,9) 2% sodium citrate tempered to 45°C (diluent for high fat foods, such as cheese),Materials,10) Sterile rods for spreading,11) Crystal Violet Stain,12) Stomacher, blender or equivalent,3 MFHPB-22,January 2004,13) Light microscope,14) Colony counting device (optional),15) Incubator capable of maintaining 22 to 25°C,16) Water bath at 45°C, as necessary to temper agar and/or to pre-warm sodium citrate,NOTE: It is the responsibility of each laboratory to ensure that the temperatures of the incubators or,water baths are maintained at the recommended temperatures. Where 35°C is recommended, the,incubator may be 35 +/- 1°C. Similarly, lower temperatures of 30 or 25°C may be +/- 1°C.,However, where hig……
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