BS EN ISO 6887-5-2010 Microbiology of food and nanimal feeding stuffs nPreparation of test samples ninitial suspension and decimal ndilutions for microbiological nexamination nPa.pdf

1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN ISO 6887-5:2010Microbiology of food andanimal feeding stuffs Preparation of test samples,initial suspension and decimaldilutions for microbiologicalexaminationPart 5: Speci

2、fic rules for the preparation ofmilk and milk products (ISO 6887-5:2010)BS EN ISO 6887-5:2010 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN ISO6887-5:2010.The UK participation in its preparation was entrusted to TechnicalCommittee AW/9, Microbiology.A list of

3、organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2010ISBN 978 0 580 59961 3ICS 07.100.30; 67.100.01Compliance with a Bri

4、tish Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 30 September 2010.Amendments issued since publicationDate Text affectedEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 6887-5 A

5、ugust 2010 ICS 07.100.30 Supersedes EN ISO 8261:2001English Version Microbiology of food and animal feeding stuffs - Preparation of test samples, initial suspension and decimal dilutions for microbiological examination - Part 5: Specific rules for the preparation of milk and milk products (ISO 6887-

6、5:2010) Microbiologie des aliments - Prparation des chantillons, de la suspension mre et des dilutions dcimales en vue de lexamen microbiologique - Partie 5: Rgles spcifiques pour la prparation du lait et des produits laitiers (ISO 6887-5:2010) Mikrobiologie von Lebensmitteln und Futtermitteln - Vor

7、bereitung von Untersuchungsproben und Herstellung von Erstverdnnungen und von Dezimalverdnnungen fr mikrobiologische Untersuchungen - Teil 5: Spezifische Regeln fr die Vorbereitung von Milch und Milcherzeugnissen (ISO 6887-5:2010) This European Standard was approved by CEN on 25 March 2010. CEN memb

8、ers are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on applicati

9、on to the CEN Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has t

10、he same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Pola

11、nd, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2010 CEN All rights of exploitation in any form and by a

12、ny means reserved worldwide for CEN national Members. Ref. No. EN ISO 6887-5:2010: EBS EN ISO 6887-5:2010EN ISO 6887-5:2010 (E) 3 Foreword This document (EN ISO 6887-5:2010) has been prepared by Technical Committee ISO/TC 34 “Food products“ in collaboration with Technical Committee CEN/TC 275 “Food

13、analysis - Horizontal methods” the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by February 2011, and conflicting national standards shall be withdrawn at the

14、latest by February 2011. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document supersedes EN ISO 8261:2001. According to the C

15、EN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, L

16、ithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 6887-5:2010 has been approved by CEN as a EN ISO 6887-5:2010 without any modification. BS EN ISO 6887-5:2010ISO 6887-

17、5:2010(E) ISO 2010 All rights reserved iiiContents Page Foreword iv 1 Scope1 2 Normative references1 3 Terms and definitions .2 4 Principle2 5 Diluents.3 6 Apparatus.7 7 Preparation of samples.7 7.1 Frozen products 7 7.2 Hard and dry products8 7.3 Liquid and non-viscous products8 7.4 Heterogeneous p

18、roducts8 8 General procedures.8 8.1 General .8 8.2 Sampling.8 8.3 General case for acidic products.8 8.4 High-fat foods (fat content 20 % mass fraction) .9 9 Specific procedures 9 9.1 Milk and liquid milk products.9 9.2 Dried milk, dried sweet whey, dried acid whey, dried buttermilk, and lactose.9 9

19、.3 Cheese and processed cheese 9 9.4 Acid casein, lactic casein, rennet casein, and caseinate10 9.5 Butter 11 9.6 Ice-cream11 9.7 Custard, desserts and sweet cream (pH 5)11 9.8 Fermented milk and sour cream (pH 20 % mass fraction) The use of a diluent with between 1 g/l and 10 g/l of added sorbitan

20、monooleate polysorbate 803), approximately according to fat levels (e.g. at a fat content of 40 %, add 4 g/l) may improve emulsification during suspension. 9 Specific procedures 9.1 Milk and liquid milk products Mix the test sample thoroughly so that the microorganisms are distributed as evenly as p

21、ossible by rapidly inverting the sample container 25 times. Avoid foaming or allow any foam to disperse. The interval between mixing and removing the test portion shall not exceed 3 min. Remove at least 1 ml of test sample with a sterile pipette and add a nine-fold volume of diluent for general use

22、(5.2). Shake this primary dilution e.g. 25 times with a movement of about 300 mm for 7 s manually, or using a vortex mixer (6.2) for 5 s to 10 s to obtain a 101dilution. Prepare further dilutions in accordance with Clause 10. 9.2 Dried milk, dried sweet whey, dried acid whey, dried buttermilk, and l

23、actose Thoroughly mix the contents of the closed container by repeatedly shaking and inverting it. If the test sample is in the original unopened container and this is too full to permit thorough mixing, transfer it to a larger container, then mix. Open the container, remove the test portion require

24、d with a spatula and proceed as indicated below. Immediately close the container again. Weigh 10 g of the test sample into a sterile glass vessel (e.g. a beaker) and then add the powder to the dilution bottle containing a diluent for general use (5.2). For dried acid whey, use dipotassium hydrogenph

25、osphate solution (5.3.2) at pH 8,4 0,2 or, if necessary, use for roller-dried milk sodium citrate solution (5.3.1) or dipotassium hydrogenphosphate solution (5.3.2) at pH 7,5 0,2. Alternatively, weigh 10 g of the test sample directly into the bottle with the required diluent. NOTE For better reconst

26、itution and in particular with roller-dried milk, glass beads (6.3) can be helpful. If used, they should be added to the bottle before sterilization. To dissolve the test sample, swirl slowly to wet the powder then shake the bottle e.g. 25 times, with a movement of about 300 mm, for about 7 s. A per

27、istaltic blender (6.1) may be used as an alternative to shaking. Allow to stand for 5 min, shaking occasionally. The diluent may be pre-warmed to 45 C if a homogeneous suspension cannot be obtained even after blending. Mention such an additional procedure in the test report. Prepare further dilution

28、s in accordance with Clause 10. 9.3 Cheese and processed cheese Weigh 10 g of test sample in a dish and transfer it to the container of a rotary blender or of a peristaltic blender (6.1). Alternatively, weigh 10 g of test sample directly into the container. 3) Tween 80 is an example of a suitable pr

29、oduct available commercially. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of this product. BS EN ISO 6887-5:2010ISO 6887-5:2010(E) 10 ISO 2010 All rights reservedAdd 90 ml of diluent for general use (5.2) or, as diluent for ch

30、eese, 90 ml of sodium citrate solution (5.3.1) or dipotassium hydrogenphosphate solution (5.3.2) at pH 7,5 0,2. Blend until the cheese is thoroughly dispersed. Allow any foam to disperse. The diluent may be pre-warmed to 45 C if a homogeneous suspension cannot be obtained even after blending. Mentio

31、n such an additional procedure in the test report. Prepare further dilutions in accordance with Clause 10. 9.4 Acid casein, lactic casein, rennet casein, and caseinate 9.4.1 General case Thoroughly mix the contents of the closed container by repeatedly shaking and inverting it. Weigh 10 g of the tes

32、t sample into a sterile plastic bag for a peristaltic blender (6.1). Add 90 ml of the appropriate diluent at room temperature, as follows: a) for acid and lactic casein dilute with dipotassium hydrogenphosphate solution with antifoam agent (5.3.3) at pH 8,4 0,2; b) for caseinate dilute with citrate

33、solution (5.3.1) or dipotassium hydrogenphosphate solution (5.3.2) at pH 7,5 0,2 or peptone-salt solution (5.2.1); c) for rennet casein dilute with dipotassium hydrogenphosphate solution with antifoam agent (5.3.3) at pH 7,5 0,2. Mix well manually and allow to stand at room temperature for 15 min. B

34、lend if necessary for 2 min in the peristaltic blender (6.1) by using two sterile bags for granular products. Allow to stand for 5 min. Prepare further dilutions in accordance with Clause 10. 9.4.2 Special case: rennet casein Rennet casein can be difficult to dissolve. An alternative procedure to th

35、at described in 9.4.1 may be used. Using dipotassium hydrogenphosphate solution with antifoam agent (5.3.3) as diluent for rennet caseins may not be efficient to dissolve the grains. These casein grains hamper the enumeration of microorganisms at 30 C. Therefore, the following alternative procedure

36、is recommended. If necessary, grind the dry casein before taking the test portion. Transfer approximately 20 g of the test sample into a suitable container. Grind it using an apparatus with knives able to rotate at approximately 20 000 r/min, equipped with a device that prevents the sample from heat

37、ing during grinding4). Weigh 5 g of the thus-prepared test sample in a sterile bottle of 250 ml. Add glass beads (6.3) for mixing and 95 ml of the sodium tripolyphosphate solution (5.3.4) preheated to 37 C. Mix by leaving the bottle on a mixing device for 15 min. Then place it in the water bath (6.4

38、) set at 37 C for 15 min while mixing from time to time. Prepare further dilutions in accordance with Clause 10. 4) The VirTis apparatus is an example of a suitable product available commercially. This information is given for the convenience of users of this document and does not constitute an endo

39、rsement by ISO of this product. BS EN ISO 6887-5:2010ISO 6887-5:2010(E) ISO 2010 All rights reserved 119.5 Butter If it is necessary to exclude the surface of a butter sample from investigation, consult ISO 707|IDF 50. Weigh 10 g of test sample into a sample container. Place the container in the wat

40、er bath (6.4) set at 45 C. Keep it in the water bath until the whole test portion has just melted. Add 90 ml of diluent for general use (5.2) warmed to 45 C and mix. This operation is more easily carried out in a peristaltic blender (6.1). Alternatively, use only the aqueous phase for dilution, as f

41、ollows. Take a test portion of 50 g containing a volume-to-mass ratio of water of W %. Add (50 50 W/100) ml of diluent for general use (5.2) pre-warmed in the water bath (6.4) at 45 C. In these conditions, 1 ml of the aqueous phase corresponds to 1 g of butter. EXAMPLE For 50 g butter containing a v

42、olume-to-mass ratio of water of about 16 %, the aqueous phase represents 8 ml of liquid. Add (50 50 16/100) = 42 ml of diluent for general use (5.2) pre-warmed in the water bath (6.4) at 45 C. Place a container in the water bath (6.4) set at 45 C until the butter melts. Remove from the water bath, s

43、hake well, and allow phases to separate for no longer than 15 min. If necessary, remove the fat phase with a spatula or a glass rod (6.5). If necessary, to separate the phases, transfer the melted test portion to a sterile centrifuge tube (or melt the test portion directly in the tube) and centrifug

44、e at a rotational frequency allowing phases to separate. It may be necessary to remove the fatty (upper) phase aseptically with a sterile tube connected to a vacuum pump. Pipette from the bottom layer. Prepare further dilutions in accordance with Clause 10. 9.6 Ice-cream Weigh 10 g of test sample in

45、to a flask or into a sterile plastic bag for a peristaltic blender (6.1). Add 90 ml of diluent at room temperature and blend. The product melts during blending. Prepare further dilutions in accordance with Clause 10. 9.7 Custard, desserts and sweet cream (pH 5) Weigh 10 g of test sample into a flask

46、 containing glass beads (6.3). Add 90 ml of diluent for general use (5.2) at room temperature and shake to disperse. Alternatively, a peristaltic blender (6.1) may be used following the manufacturers instructions. In this case, the bag should not contain any glass beads. Prepare further dilutions in

47、 accordance with Clause 10. 9.8 Fermented milk and sour cream (pH 5) Weigh 10 g of test sample into a flask containing glass beads (6.3). Add as diluent 90 ml of buffered peptone water (5.2.5) or dipotassium hydrogenphosphate solution (5.3.2) at pH 7,5 0,2 at room temperature and shake manually. Alt

48、ernatively, a peristaltic blender (6.1) may be used following the manufacturers instructions. In this case, the bag should not contain any glass beads. Prepare further dilutions in accordance with Clause 10. 9.9 Milk-based infant foods Thoroughly mix the contents of the closed container by repeatedl

49、y shaking and inverting it. If the test sample is in an original unopened container which is too full to permit thorough mixing, transfer it to a larger container, then mix. Open the container. Remove the required test portion with a spatula (6.5) and proceed as indicated below. Immediately close the container again. BS EN ISO 6887-5:2010ISO 6887-5:2010(E) 12 ISO 2010 All rights reservedWeigh 10 g of test sample into a suitable sterile glass vessel (e.g. a beaker). Then add the powder to the dilution bott