MFO-4 Microbiological Examination of Cottage Cheese
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CBFE38D0D7B14680BAD73244D0FD3F02 |
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文件大小(MB)： |
0.02 |
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页数： |
7 |
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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,Official Method MFO-4,November 30, 1981,HEALTH PROTECTION BRANCH,OTTAWA,MICROBIOLOGICAL EXAMINATION OF COTTAGE CHEESE,1. APPLICATION,This method shall be used for the determination of coliform bacteria (Coliforms) in cottage cheese in,accordance with Section B.08.054 of the Food and Drug Regulations.,2. SAMPLING,2.1 Definition of Terms,2.1.1 Lot: A batch or production unit which may be identified by the same code. When there is no,code identification, a lot may be considered as (a) that quantity of cottage cheese produced under,essentially the same conditions, at the same establishment and representing no more than one,day's production; or, (b) the quantity of the same variety of cottage cheese from one and the,same manufacturer available for sampling at a fixed location.,2.1.2 Sample: The sample units (subsamples) taken from a lot for analysis.,2.1.3 Sample Unit: Usually a consumer size container of the product, and should consist of a minimum,of 100 g. A sample unit is often referred to as a subsample.,2.1.4 Analytical Unit: That amount of product withdrawn from the sample unit for analysis.,2.2 Collection of Samples,2.2.1 A sample, consisting of five sample units drawn at random from each lot, shall be taken.,2.2.2 Each sample unit shall consist of at least 100 g.,2.2.3 Collect original unopened containers wherever possible.,2.2.4 More than one sample unit may be collected from large institutional or bulk containers when the,total number of sample units required exceeds the number of containers in the lot. When the lot,consists of containers smaller than 100 g, a sample unit will consist of more than one containers,(e.g., four 25 g containers in each sample unit).,2.2.5 Employ aseptic techniques in collecting the sample units when sampling from bulk. Place each,collected sample unit into a separate sterile container.,MFO-4,- 2 - November 30, 1981,2.2.6 Keep sample units refrigerated (0-5oC) during transport.,3. PROCEDURE,Each sample unit shall be analyzed individually. The test shall be carried out in accordance with the following,instructions:,3.1 Handling of Sample Units,3.1.1 Keep sample units refrigerated (0-5oC) in the laboratory prior to analyzing them.,3.1.2 Analyze the sample units as soon as possible after they have been received in the laboratory.,3.2 Preparation of media,The following media, prepared and sterilized according to the manufacturer's instructions, shall,be used:,3.2.1 Lauryl Sulfate Tryptose (LST) broth,3.2.2 Brilliant Green Lactose 2% Bile (BGLB) broth,3.3 Preparation of Dilutions,3.3.1 Prepare sterile 2% sodium citrate solution and temper to 40-45oC.,3.3.2 Combine portions from several locations within the sample unit to ensure a representative,analytical unit of 11(10)* g.,* Weight and volume in brackets indicate alternate procedure for making dilutions.,3.3.3 Prepare a 1:10 dilution of the cottage cheese by aseptically adding the analytical unit to 99(90)*,ml of the sodium citrate in a sterile blender jar. Blend for the minimum time required to produce,a homogeneous suspension. To prevent overheating, blending time should not exceed 2.5 min.,3.3.4 Check the pH of the suspension. If the pH is outside the range of 5.5 to 7.6, adjust to 7.0, with,either sterile NaOH or HCl.,3.4 Determination of Coliforms,3.4.1 Presumptive Test,a. The medium used is LST broth, dispensed in 10 ml volumes into tubes containing gas,vials (inverted Durham tubes).,b. Arrange LST broth tubes in rows of five, and mark them identifying the sample, the,sample unit and the dilution to be inoculated.,c. Inoculate each tube of a set of five tubes of single strength LST broth with 1 ml of the 1:10,dilution (cottage cheese homogenate; see section 3.3, above). Repeat for each,succeeding decimal dilution as required.,d. Mix inoculum and medium by gently shaking or rotating the tubes, but avoid entrapping,MFO-4,- 3 - November 30, 1981,air in the gas vials.,e. Incubate the inoculated LST broth tubes at 35oC + 0.5o for 24 + 2 hr. Examine for gas,formation, record results, and on the same day begin the confirmed test for all gas-positive,tubes (see section 3.4.2, below).,f. Incubate gas-negative tubes for an additional 24 + 2 hr, examine, record the number of,gas-positive tubes, add to the results obtained in step e., above, and begin the confirmed,test for the additional gas-positive tubes.,g. The absence of gas in all of the tubes at the end of 48 + 2 hr of incubation constitutes a,negative pre……
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