BS 4285-3 2-1991 Microbiological examination for dairy purposes - Methods for detection and or enumeration of specific groups of microorganisms - Enumeration of thermoduric bacteri.pdf

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1、BRITISH STANDARD BS4285-3.2: 1991 Incorporating Amendment No.1 Microbiological examination for dairy purposes Part 3: Methods for detection and/or enumeration of specific groups of microorganisms Section3.2 Enumeration of thermoduric bacteria IMPORTANT NOTE. It is essential that Parts0 and1 and Sect

2、ion2.1 of thisstandard,which are published separately, be read in conjunction withthisSectionBS4285-3.2:1991 This British Standard, having been prepared under the directionof the Agriculture and Food Standards Policy Committee,was published under the authority of the Board of BSI and comes into effe

3、ct on 31January 1991 BSI 03-1999 BS4285 first published March1968 Supplement No.1 to BS4285:1968first published April1970 Second edition, as Section3.2, May 1985 Third edition January 1991 The following BSI references relate to the work on this standard: Committee reference AFC/14 Draft for comment9

4、0/54466 DC ISBN 0 580 19326 8 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Agriculture and Food Standards Policy Committee (AFC/-) to Technical Committee AFC/14, upon which the following bodies were represented: AFRC Institute of Food

5、 Research Association of British Preserved Milk Manufacturers Association of Public Analysts British Food Manufacturing Industries Research Association Campden Food and Drink Research Association Dairy Trade Federation Department of Trade and Industry (Laboratory of the Government Chemist) Joint Com

6、mittee of the Milk Marketing Board and the Dairy Trade Federation Milk Marketing Board Milk Marketing Board for Northern Ireland Ministry of Agriculture, Fisheries and Food Public Health Laboratory Service Scottish Milk Marketing Board Society for Applied Bacteriology Society for General Microbiolog

7、y Amendments issued since publication Amd. No. Date Comments 6985 February 1992 Indicated by a sideline in the marginBS4285-3.2:1991 BSI 03-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definition 1 3 Principle 1 4 Diluents and culture media 1 5 Apparatus 1 6

8、 Sampling 1 7 Preparation of the test sample 1 8 Procedure 1 9 Calculation and expression of results 1 10 Test report 1 Publication(s) referred to Inside back coverBS4285-3.2:1991 ii BSI 03-1999 Foreword This Section of BS4285 has been prepared under the direction of the Agriculture and Food Standar

9、ds Policy Committee. It supersedes BS4285-3.2:1985 which is withdrawn. This revision introduces a lower temperature for enumeration (30 C in place of37 C) as this temperature has been found to produce a more onerous test condition. A British Standard does not purport to include all the necessary pro

10、visions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 and2, a

11、n inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.BS4285-3.2:1991 BSI 03-1999 1 1 Scope This Section of BS4285 describes a method for the enumerati

12、on of thermoduric bacteria present in milk and milk products. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definition For the purposes of this Section of BS4285, the following definition applies. thermoduric bacteria those bacteria surviving

13、pasteurization at63.5 C for30min and which can then form countable colonies when grown under the conditions specified 3 Principle A test portion is heated at63.5 C in a water bath and the surviving bacteria are enumerated using the poured plate technique for colony count described in BS4285-2.1. 4 D

14、iluents and culture media Use the diluents and culture media described in BS4285-1.2. 5 Apparatus NOTEFor details of apparatus including its preparation and sterilization, see BS4285-1.2. 5.1 Ordinary microbiological laboratory apparatus. 5.2 Apparatus for the poured plate technique, as given in BS4

15、285-2.1. 5.3 Incubator, capable of being controlled at30 1 C. 5.4 Water bath, capable of being controlled at63.5 0.5 C (see8.1.3). 5.5 Total delivery pipettes, of10mL nominal capacity. 5.6 Universal containers or McCartney bottles, of30mL nominal capacity, with metal screw caps having rubber or simi

16、lar liners to give secure closures (see8.1.3). 6 Sampling Take the laboratory sample in accordance with BS4285-1.1. 7 Preparation of the test sample Prepare the test sample from the laboratory sample in accordance with BS4285-1.1. 8 Procedure 8.1 Laboratory pasteurization of the test sample 8.1.1 Re

17、move the cap of the container (5.6), add10mL of the test sample (see BS4285-1.1) and replace the cap tightly. 8.1.2 Completely immerse the container in water at63.5 0.5 C in the water bath (5.4). After35min remove the container from the water bath and immediately cool in water to20 C. Discard any sa

18、mples showing signs of curdling and report this action in the test report (see clause10). 8.1.3 Ensure that the rate of heating of the samples is such that they reach63 C within5min by carrying out the following procedure. Fit a thermometer (reading to0.1 C) through the cap of a container so that no

19、 leaks occur and so that it can reach into a10mL sample. Place 10mL of milk in a container, screw the cap with thermometer into place and immerse the container in the water whilst a test is being carried out. Note the time taken to reach63 C. Failure to reach63 C within5min may be due to poor heat t

20、ransfer through the containers in which case they should be changed, or to overloading the water bath in which case fewer containers should be used or the agitation of the water increased. 8.2 Enumeration of surviving bacteria Immediately after the cooling procedure (see8.1.2), carry out the procedu

21、re described in BS4285-2.1, incubating the plates for3days in the incubator(5.3),controlled at30 1 C. 9 Calculation and expression of results Calculate the number of organisms in accordance with BS4285-2.1. Express the results as numbers of thermoduric bacteria per gram or per millilitre of sample.

22、10 Test report The test report shall give the number and date of this standard, i.e.BS4285-3.2:1991 and state the results obtained. It shall also state all operating conditions not specified in this standard or regarded as optional, as well as any circumstances that may have influenced the result. T

23、he report shall include all details required for complete identification of the sample.2 blankBS4285-3.2:1991 BSI 03-1999 Publication(s) referred to BS4285, Microbiological examination for dairy purposes. BS4285-0, General introduction. BS4285-1, Guide to general procedures. BS4285-1.1, Sampling and

24、 preparation of sample. BS4285-1.2, Diluents, media and apparatus and their preparation and sterilization. BS4285-2.1, Enumeration of microorganisms by poured plate technique for colony count. BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

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