MFO-2 Microbiological Examination of Ice Cream and Ice Milk
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9A084FDBBC424564BF9B8CC737570088 |
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0.02 |
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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: (514) 688-1930.,Government of Canada Gouvernement du Canada,Official Method MFO-2,November 30, 1981,HEALTH PROTECTION BRANCH,OTTAWA,MICROBIOLOGICAL EXAMINATION OF ICE CREAM AND ICE MILK,1. APPLICATION,This method shall be used for the determination of total aerobic bacteria (Aerobic Colony Count) and,coliform bacteria (Coliforms) in ice cream or ice milk in accordance with sub-paragraph (d) of sections,B.08.062 and B.08.072, respectively of the Food and Drug Regulations.,2. SAMPLING,2.1 Definition of Terms,See Appendix A of Volume 1,2.2 Collection of Samples,See Appendix B of Volume 1,3. PROCEDURE,Each sample unit shall be analyzed individually. The tests shall be carried out on the sample in accordance,with the following instructions:,3.1 Handling of Sampling Units,3.1.1 Keep the sample units frozen in the laboratory before analyzing them.,3.1.2 Analyze the sample units as soon as possible after they have been received at the laboratory.,3.2 Preparation of media,The following media, to be prepared and sterilized according to the manufacturer's instructions, shall,be used:,3.2.1 Plate Count (PC) agar,3.2.2 Lauryl Sulfate Tryptose (LST) broth,3.2.3 Brilliant Green Lactose 2% Bile (BGLB) broth,3.3 Preparation of Dilutions,3.3.1 Prepare sterile 0.1% peptone water diluent.,3.3.2 Combine portions from several locations within the frozen sample unit to ensure a representative,analytical unit of 11 (10)g. Weight or volume in brackets indicate alternate procedure for making dilutions.,MFO-2,- 2 - November 30, 1981,3.3.3 Prepare a 1:10 dilution of the ice cream or ice milk by aseptically adding the analytical unit into,99(90) ml of the peptone water diluent.,3.3.4 Mix the 1:10 dilution by shaking the dilution bottle 25 times in a 30 cm arc in approximately 7 sec.,3.3.5 Check the pH of the dilution. If the pH is outside the range of 5.5 to 7.6, adjust to 7.0, with either,sterile NaOH or HCl.,3.3.6 Prepare succeeding dilutions as required to determine the ACC and the number of Coliforms present,in the ice cream by transferring 11(10) ml of the previous dilution into 99(90) ml of 0.1% peptone,water diluent. Shake all dilutions (as in step 3.3.4, above) immediately prior to making transfers to,ensure uniform distribution of the microorganisms present.,3.4 Determination of the ACC,The medium used is PC agar prepared for making pour plates.,3.4.1 Analysis,a. Agitate each dilution bottle to resuspend material.,b. Without delay, pipette 1 ml of each prepared dilution into each of two approproately marked Petri,plates using a sterile pipette for each transfer.,c. Pour 12-15 ml of the tempered agar (40-45°C) into each plate and mix contents by rotating and,tilting.,d. Allow agar to solidify.,e. Plates shall be poured not late than 15 min. after preparation of dilutions.,f. Incubate plates in an inverted position at 35 + 0.5°C for 48 + 2 hr.,g. Avoid crowding or excessice stacking of plates in order to permit rapid equilibration of plates with,incubator temperature.,h. Count colonies promptly after the incubation temperature.,3.5 Determination of Coliforms,3.5.1 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 fives, 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 (ice cream or milk suspension; see section 3.3, above). Repeat for each succeeding,decimal solution as required.,d. Mix inoculum and medium by gently shaking or rotating the tubes, but avoid entrapping air,in the gas vials.,e. Incubate the inoculated LST broth tubes at 35 ± 0.5oC 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 3.5.2, below).,MFO-2,- 3 - November 30, 1981,f. Incubate gas-negative tubes for an additional 24 ± 2 hr, examine, record the number of,gas-positive tubes, add to the result 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 presumptive test.,h. Compute the "MPN" of presumptive coliforms per g of ice cream or ice milk following the,instructions in Part 5, to convert the number of gas-positive tubes to MPN values. Record,results.,3.5.2 Confirmed Test,a. The confirmatory medium used……
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