SIST EN ISO 6887-1:2017

SLOVENSKI STANDARD
01-junij-2017
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SIST EN ISO 6887-1:1999
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Microbiology of the food chain - Preparation of test samples, initial suspension and
decimal dilutions for microbiological examination - Part 1: General rules for the
preparation of the initial suspension and decimal dilutions (ISO 6887-1:2017)
Mikrobiologie der Lebensmittelkette - Vorbereitung von Untersuchungsproben und
Herstellung von Erstverdünnungen und von Dezimalverdünnungen für mikrobiologische
Untersuchungen - Teil 1: Allgemeine Regeln für die Herstellung von Erstverdünnungen
und Dezimalverdünnungen (ISO 6887-1:2017)
Microbiologie des aliments - Préparation des échantillons, de la suspension mère et des
dilutions décimales en vue de l'examen microbiologique - Partie 1: Règles générales
pour la préparation de la suspension mère et des dilutions décimales (ISO 6887-1:2017)
Ta slovenski standard je istoveten z: EN ISO 6887-1:2017
ICS:
07.100.30 Mikrobiologija živil Food microbiology
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 6887-1
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2017
EUROPÄISCHE NORM
ICS 07.100.30 Supersedes EN ISO 6887-1:1999
English Version
Microbiology of the food chain - Preparation of test
samples, initial suspension and decimal dilutions for
microbiological examination - Part 1: General rules for the
preparation of the initial suspension and decimal dilutions
(ISO 6887-1:2017)
Microbiologie de la chaîne alimentaire - Préparation Mikrobiologie der Lebensmittelkette - Vorbereitung
des échantillons, de la suspension mère et des dilutions von Untersuchungsproben und Herstellung von
décimales en vue de l'examen microbiologique - Partie Erstverdünnungen und von Dezimalverdünnungen für
1: Règles générales pour la préparation de la mikrobiologische Untersuchungen - Teil 1: Allgemeine
suspension mère et des dilutions décimales (ISO 6887- Regeln für die Herstellung von Erstverdünnungen und
1:2017) Dezimalverdünnungen (ISO 6887-1:2017)
This European Standard was approved by CEN on 14 January 2017.

CEN members 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 application to the CEN-CENELEC 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-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6887-1:2017 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 6887-1:2017) has been prepared by Technical Committee ISO/TC 34 "Food
products" in collaboration with Technical Committee CEN/TC 275 “Food 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 October 2017, and conflicting national standards shall
be withdrawn at the latest by October 2017.
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 6887-1:1999.
According to the CEN-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, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 6887-1:2017 has been approved by CEN as EN ISO 6887-1:2017 without any
modification.
INTERNATIONAL ISO
STANDARD 6887-1
Second edition
2017-03
Microbiology of the food chain —
Preparation of test samples, initial
suspension and decimal dilutions for
microbiological examination —
Part 1:
General rules for the preparation of
the initial suspension and decimal
dilutions
Microbiologie de la chaîne alimentaire — Préparation des
échantillons, de la suspension mère et des dilutions décimales en vue
de l’examen microbiologique —
Partie 1: Règles générales pour la préparation de la suspension mère
et des dilutions décimales
Reference number
ISO 6887-1:2017(E)
©
ISO 2017
ISO 6887-1:2017(E)
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
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Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved

ISO 6887-1:2017(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Diluents . 3
5.1 Basic materials . 3
5.2 Diluents for general use . 3
5.2.1 Peptone salt solution . 3
5.2.2 Buffered peptone water . 4
5.2.3 Double-strength buffered peptone water . 4
5.3 Diluents for special purposes . 4
5.4 Distribution and sterilization of the diluent . 4
5.5 Performance testing for diluents . 5
6 Apparatus . 5
7 Sampling . 6
8 Preparation of samples. 6
8.1 General . 6
8.2 Frozen products . 7
8.2.1 General. 7
8.2.2 Small samples defrosted before testing . 7
8.2.3 Large pieces or blocks sampled while frozen . 7
8.3 Hard and dry products . 8
8.4 Dehydrated and other low-moisture products. 8
8.5 Liquid and non-viscous products. 8
8.6 Acidic products . 8
8.7 High-fat (over 20 %) foods . 9
8.8 Multi-component products. 9
8.9 Packaged products . 9
8.10 Surface samples (swabs and other devices) .10
9 Specific procedures.10
9.1 Test portion and initial suspension (primary dilution) .10
9.2 Duration of the procedure .11
9.3 Pooling and compositing procedures for qualitative tests.11
10 Further dilutions .11
10.1 Decimal dilution series .11
10.2 Other dilution series .12
Annex A (informative) Illustrations of pooling and compositing procedures.13
Annex B (informative) Method for sampling frozen test pieces or blocks .18
Annex C (informative) Data showing reliability of test results according to size of test portions .20
Annex D (informative) Verification protocol for pooling samples for qualitative tests .23
Bibliography .26
ISO 6887-1:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www . i so .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 9,
Microbiology.
This second edition cancels and replaces the first edition (ISO 6887-1:1999), which has been technically
revised.
A list of parts in the ISO 6887 series can be found on the ISO website.
iv © ISO 2017 – All rights reserved

ISO 6887-1:2017(E)
Introduction
Because of the large variety of food and animal feed products, this horizontal method might not be
appropriate in every detail for certain products. In this case, different methods which are specific to
these products can be used if absolutely necessary for justified technical reasons.
When this document is next reviewed, account will be taken of all information then available regarding
the extent to which this horizontal method has been followed and the reasons for deviations from this
method in the case of particular products.
The harmonization of test methods cannot be immediate and for certain groups of products,
International Standards and/or national standards may already exist that do not comply with this
horizontal method. It is hoped that when such standards are reviewed, they will be changed to comply
with this document so that eventually, the only remaining departures from this horizontal method will
be those necessary for well-established technical reasons.
This document defines the general rules for the preparation of samples, initial suspensions and
subsequent dilutions for microbiological examination. The remaining parts of ISO 6887 give specific
rules for the preparation of samples and initial suspensions, each covering the variety of food and feed
products and environmental samples to which ISO 6887 applies.
For a number of products, it is necessary to take special precautions, especially when preparing the
initial suspension, because of the physical state of the product (such as dry products, highly viscous
products) or the presence of inhibitory substances (such as spices, high salt content) or the acidity, etc.
These are covered in general terms in this document.
Any special diluents or practices required for particular products or microorganisms in specific
standard methods take priority over the general rules listed in the ISO 6887 series. These can include
the following:
— specific rehydration procedures for foods of low water activity to minimize osmotic shock;
— the use of adequate temperatures to aid suspension of cocoa, gelatine, milk powder, etc.;
— resuscitation procedures for the improved recovery of stressed microorganisms resulting from
food processing and storage;
— homogenization procedures and duration specific to certain products (e.g. cereals) and/or to certain
determinations (e.g. yeasts and moulds).
INTERNATIONAL STANDARD ISO 6887-1:2017(E)
Microbiology of the food chain — Preparation of test
samples, initial suspension and decimal dilutions for
microbiological examination —
Part 1:
General rules for the preparation of the initial suspension
and decimal dilutions
WARNING — The use of this document may involve hazardous materials, operations and
equipment. It is the responsibility of the user of this document to establish appropriate safety
and health practices and to determine the applicability of regulatory limitations before use.
1 Scope
This document defines general rules for the aerobic preparation of the initial suspension and of dilutions
for microbiological examinations of products intended for human or animal consumption.
This document is applicable to the general case and other parts apply to specific groups of products
as mentioned in the foreword. Some aspects might also be applicable to molecular methods where
matrices can be associated with inhibition of the PCR steps and consequently affect the test result.
This document excludes preparation of samples for both enumeration and detection test methods
where preparation instructions are detailed in specific International Standards.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 7218, Microbiology of food and animal feeding stuffs — General requirements and guidance for
microbiological examinations
ISO 11133, Microbiology of food, animal feed and water — Preparation, production, storage and
performance testing of culture media
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
laboratory sample
sample prepared for sending to the laboratory and intended for inspection or testing
[SOURCE: ISO 7002:1986, A.19]
ISO 6887-1:2017(E)
3.2
composite sample
mixed sample of a number of the same items of food, animal feed, animals or environment, from which
a test portion is taken for examination in the laboratory
Note 1 to entry: See illustration of a composite sample in Annex A.
3.3
pooled sample
mixed sample of a number of the same items of food, animal feed, animals or environment, where the
complete mixture is the test portion and is taken as a whole for examination in the laboratory
Note 1 to entry: See illustration of a pooled sample in Annex A.
3.4
test sample
sample prepared from the laboratory sample (3.1) according to the procedure specified in the method of
test and from which test portions (3.5) are taken
Note 1 to entry: Preparation of the laboratory sample before the test portion is taken is infrequently used in
microbiological examinations.
[SOURCE: ISO 7002:1986, A.47]
3.5
test portion
measured (volume or mass) representative sample taken from the laboratory sample (3.1) for use in the
preparation of the initial suspension (3.6)
Note 1 to entry: Sometimes preparation of the laboratory sample (3.1) is required before the test portion is taken,
but this is infrequently used in microbiological examinations.
3.6
initial suspension
primary dilution
suspension, solution or emulsion obtained after a weighed or measured quantity of the product under
examination (or of a test sample prepared from the product) has been mixed with, normally, a nine-fold
quantity of diluent, allowing large particles, if present, to settle
Note 1 to entry: Nine-fold quantities of diluent are normally used to produce a decimal dilution series, but other
ratios may be required for specific purposes, such as to enumerate low numbers.
3.7
further dilution
suspension or solution obtained by mixing a measured volume of the initial suspension (3.6) with an
x-fold volume of diluent and by repeating this operation with further dilutions until a dilution series,
suitable for the inoculation of culture media, is obtained
Note 1 to entry: Ten-fold dilutions are normally used to produce a decimal dilution series, but other ratios may be
required for specific purposes.
3.8
pooled test portions
mixture of test portions from a number of the same items of food, animal feed, animals or environment,
where the complete mixture is the test portion examined
Note 1 to entry: See illustration of pooled test portions in Annex A.
2 © ISO 2017 – All rights reserved

ISO 6887-1:2017(E)
3.9
pooled (pre-)enriched test portions
individually (pre-)enriched test portions from a number of the same items of food, animal feed, animals
or environment, from which specified volumes are combined for further examination
Note 1 to entry: See illustration of pooled (pre-)enriched test portions in Annex A.
3.10
specific standard
International Standard or guidance document describing the examination of a specific product (or group
of products) for the detection or enumeration of a specific microorganism (or group of microorganisms)
4 Principle
Preparation of the initial suspension (3.6) in such a way as to obtain as uniform a distribution as
possible of the microorganisms contained in the test portion (3.5).
Preparation, if necessary, of further dilutions (3.7) in order to reduce the number of microorganisms
per unit volume to allow, after incubation, observation of their growth or not (in the case of tubes or
bottles) or colony counting (in the case of plates), as stated in each specific standard.
NOTE In order to restrict the range of enumeration to a given optimum interval, or if high numbers of
microorganisms are foreseen, it is possible to inoculate only the necessary (decimal) dilutions needed to achieve
the enumeration according to the calculations described in ISO 7218.
5 Diluents
5.1 Basic materials
To improve the reproducibility of test results, it is recommended that either ready-made diluents or
dehydrated basic components or a dehydrated complete preparation should be used. In all cases, the
manufacturer’s instructions shall be followed rigorously.
Chemical products shall be of recognized analytical quality and suitable for microbiological
examinations.
The water used shall be distilled water or of equivalent quality (see ISO 7218 or ISO 11133).
For more detailed rules on preparation and performance testing of culture media, see ISO 11133.
5.2 Diluents for general use
5.2.1 Peptone salt solution
5.2.1.1 Composition
Enzymatic digest of casein 1,0 g
Sodium chloride 8,5 g
Water 1 000 ml
5.2.1.2 Preparation
Dissolve the components in the water in flasks, bottles or test tubes (6.4) by heating, if necessary.
Adjust the pH if necessary so that, after sterilization, it is 7,0 ± 0,2 at 25 °C.
ISO 6887-1:2017(E)
5.2.2 Buffered peptone water
5.2.2.1 Composition
a
Peptone 10,0 g
Sodium chloride 5,0 g
Disodium hydrogen phosphate dodecahydrate 9,0 g
b
(Na HPO ·12H O) ‡
2 4 2
Potassium dihydrogen phosphate (KH PO ) ‡ 1,5 g
2 4
Water 1 000 ml
a
For example, enzymatic digest of casein.
b
If disodium hydrogen phosphate with a different water content is
used, amend the mass of the ingredient accordingly. For example, in
case of anhydrous disodium hydrogen phosphate (Na HPO ), use 3,57 g.
2 4
‡  Buffer ingredients, see 5.2.3.
5.2.2.2 Preparation
Dissolve the components in the water in flasks, bottles or test tubes (6.4), by heating if necessary.
Adjust the pH, if necessary, so that after sterilization, it is 7,0 ± 0,2 at 25 °C.
5.2.3 Double-strength buffered peptone water
This diluent may be necessary for high acid samples (see 8.6) and is prepared by dissolving double the
quantities of a complete dehydrated medium in 1 000 ml of water and processing in the same manner.
If the diluent is prepared from individual ingredients, only double the quantities of the two buffer
ingredients (marked ‡) are required.
5.3 Diluents for special purposes
See the specific standard or part of ISO 6887 appropriate to the product concerned.
5.4 Distribution and sterilization of the diluent
Dispense the diluent in volumes as necessary for the preparation of the initial suspensions into vessels
(6.4) of appropriate capacity.
Dispense further diluent in volumes as necessary for the preparation of the (decimal or other ratio)
dilutions into vessels (6.4) of appropriate capacity.
The tolerance allowable on final diluent volumes, after sterilization, shall not exceed ±2 %.
In order to enumerate several groups of microorganisms using different culture media, it may be
necessary to distribute all the diluents (or some of them) in quantities greater than 9,0 ml into vessels
(6.4) of appropriate size.
Stopper the vessels loosely to allow for expansion on heating.
Sterilize in the autoclave at 121 °C ± 3 °C for 15 min (see ISO 7218).
After autoclaving, check that the volumes from a proportion of the batch of diluent prepared are within
the permitted tolerance of ±2 %. This may be achieved either destructively by emptying the contents
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ISO 6887-1:2017(E)
of the vessels into a tared container after autoclaving or non-destructively by marking and weighing
vessels positioned through the autoclave both before and after autoclaving. For small batches of less
than 100 units, check at least one unit; for larger batches, check 3 % to 5 % by either method.
To ensure diluent volumes meet the permitted tolerance, autoclaving bulk volumes and dispensing the
required amounts into sterile vessels aseptically may also be used.
5.5 Performance testing for diluents
Test all diluents before use, according to Table 1, by the method given in ISO 11133.
The productivity target for diluents requires that the number of colonies counted after the specified
incubation time at laboratory ambient temperature (18 °C to 27 °C) shall be within ±30 % of the number
counted initially.
Table 1 — Test microorganisms and productivity criterion for diluents
Test WDCM Reference Control
Media Incubation Criteria
a
microorganisms number medium method
Peptone salt
diluent
Buffered peptone
45 min to 1 h
00012 or
c
water (single and Escherichia coli
at laboratory ±30 % of
double strength)
ambient TSA Quantitative original
temperature count
Staphylococcus
b
Peptone solution 00034
(18 °C to 27 °C)
aureus
Phosphate
buffered diluent
a
Refer to the reference strain catalogue available at http:// www .wfcc .info for information on culture collection strain
numbers and contact details.
b
Strain to be used as a minimum.
c
Free choice of strain; one of the strains must be used as a minimum.
6 Apparatus
Usual microbiological laboratory equipment (see ISO 7218) and, in particular, the following.
6.1 Apparatus for dry sterilization (oven) and wet sterilization (autoclave), see ISO 7218.
6.2 Homogenizer.
6.2.1 Rotary homogenizer (blender).
See ISO 7218. If a large sample is to be homogenized, the equipment should include a sterile 1 litre bowl.
6.2.2 Peristaltic homogenizer.
See ISO 7218. With sterile bags or filter bags to retain particulate material where necessary.
6.3 Mechanical stirrer, see ISO 7218.
6.4 Flasks, test tubes or screw-cap bottles, of appropriate capacities.
6.5 Total-delivery graduated pipettes, of nominal capacities 1 ml and 10 ml, graduated in 0,1 ml and
0,5 ml divisions, respectively. Mechanical pipettors of suitable accuracy may also be used (see ISO 7218).
ISO 6887-1:2017(E)
6.6 pH-meter, capable of being read to the nearest 0,01 pH unit at 25 °C, enabling measurements to be
made which are accurate to ±0,1 pH unit (see ISO 7218).
6.7 Balances and gravimetric diluters, capable of weighing to 1 % of the mass (see ISO 7218).
6.8 Sterile sample trays, of appropriate dimensions.
6.9 Sterile scissors, forceps or tongs, straight scalpels or knives, and spatulas.
6.10 Special opening equipment, such as bottle and can openers.
6.11 Equipment for collecting test portions from frozen laboratory samples.
6.11.1 Variable speed electric drill, with maximum speed in use of 900 r/min, or hand drill.
6.11.2 Sterile wood bit for electric drill, of 14 mm or 16 mm diameter.
6.11.3 Sterile wood chisel, of 20 mm width, and hammer or plastic mallet.
6.11.4 Other apparatus that does not cause overheating or contamination of the sample.
6.11.5 Equipment for cauterization of sample surfaces, e.g. portable gas blowtorch.
6.11.6 Template for surface sampling, metallic frame of appropriate dimensions to delineate the
surface to be sampled, sterilized by flaming after immersion in 70 % (volume fraction) alcohol.
6.12 Water bath, capable of being maintained at 44 °C to 47 °C or as stated for specific purposes.
6.13 Sterile wide-necked bowls, containers or plastic bags, of 500 ml capacity.
6.14 Sterile glass beads or balls, to disperse samples such as swabs.
7 Sampling
Carry out sampling in accordance with the specific standard appropriate to the product concerned or
see ISO/TS 17728. If specific sampling instructions are not available, it is recommended that agreement
be reached on this subject by the parties concerned.
Some guidance is given in other parts of ISO 6887 on sampling specific to certain products (see, for
example, ISO 6887-3).
8 Preparation of samples
8.1 General
Requirements for the different general categories of products subjected to microbiological examination
are given in this clause. For specific requirements on certain product types, see the appropriate part of
ISO 6887 for further information.
In other cases, see the specific standard appropriate to the product concerned. If such a specific
standard is not available, it is recommended that agreement be reached on this subject by the parties
concerned.
6 © ISO 2017 – All rights reserved

ISO 6887-1:2017(E)
8.2 Frozen products
8.2.1 General
Frozen products are considered under two headings:
— small laboratory samples that may be defrosted before testing;
— large pieces or blocks from which laboratory samples or test portions are taken without defrosting.
8.2.2 Small samples defrosted before testing
These samples include packaged retail products of all types (generally under 2 kg), including cuts and
portions of meat and fish, vegetables, desserts and prepared multi-component products.
All such products stored and submitted to the laboratory frozen should be brought to a consistency
that allows sampling in the original packaging. This may be achieved by standing at 18 °C to 27 °C
(laboratory ambient temperature) for a maximum of 3 h, or at 5 °C ± 3 °C for a maximum of 24 h. Store
thawing samples on separate trays (6.8) to prevent cross-contamination from any “drip” (thaw liquid)
leaking through the packaging.
Samples shall be tested as quickly as possible after this, even if the product is still partially frozen when
taking the test portion, as addition of the diluent at ambient laboratory temperature will facilitate full
defrosting.
Defrosting in a temperature-controlled water bath or under running cold water is not recommended as
this can result in contamination of the sample if the packaging is not completely watertight.
8.2.3 Large pieces or blocks sampled while frozen
8.2.3.1 General
These samples include large pieces or blocks of frozen products (generally over 2 kg), including carcases
and joints of meat, and fish that has been block frozen in bulk.
Separate the sample from any packaging using scissors or a scalpel (6.9), and place it on a tray (6.8)
with a flat side facing upwards.
Three options for sampling exist depending on the purpose of the testing and requirements of the
customer. If sampling requirements are not known or specified, these should be discussed between all
parties.
8.2.3.2 Total sample (surface and depth)
Using an electric drill (6.11.1) equipped with the appropriate bit (6.11.2) or any other apparatus (6.11.4),
or failing this, the hand drill (6.11.1), make holes in the specified points (see Annex B). Set the speed of
the drill or other apparatus to not more than 900 r/min to avoid fusion or dispersion of the shavings.
Using a sterile spatula (6.9), collect the resultant shavings and place them in a tared container or plastic
bag (6.13) to be used for homogenization. If the mass is greater than 50 g, mix the shavings thoroughly
in another container or plastic bag to provide a test sample, and then remove the final homogeneous
test portion for testing.
The entire sampling operation shall not cause a significant increase in the temperature of the sample
that would damage any microorganisms present.
ISO 6887-1:2017(E)
8.2.3.3 Sample at depth only
Using the wood chisel and hammer (6.11.3), remove a surface strip 2 mm to 3 mm thick from an area of
approximately 6 cm by 6 cm.
Cauterize the exposed area with the blowtorch (6.11.5) until the cleared surface is carbonized. Then
proceed according to 8.2.3.2, making holes in the cauterized area without penetrating through to the
lower surface of the block.
8.2.3.4 Surface only sample
Sterilize the template (6.11.6) and the wood chisel (6.11.3) by dipping in 70 % (volume fraction) alcohol
and flaming. While the template is still hot, apply it to the surface of the frozen product.
Using the sterile chisel and hammer (6.11.3), chip off the upper layer of product within the template
to a depth of 2 mm to 3 mm. Collect the resultant pieces and place them in a tared container or plastic
bag (6.13) to be used for homogenization.
8.3 Hard and dry products
Do not homogenize hard or dry products in a rotary homogenizer for more than 2,5 min at one time to
avoid an excessive rise in temperature.
For some hard and dry products, it may be necessary to mince or to grind the laboratory sample. In this
case, to avoid an excessive rise in temperature, do not mince or grind for more than 1 min.
8.4 Dehydrated and other low-moisture products
Mix powdered products thoroughly in their container and then weigh out using aseptic techniques.
Other products may require breaking or cutting up into small pieces with sterile tools (6.9) before
sampling.
For dehydrated and other low-moisture products, it is important to weigh the diluent and then add the
test portion to reduce osmotic shock on any microorganisms present.
Low-moisture products may require a period (up to 1 h) soaking in the diluent used for the initial
suspension to soften them before homogenization and subsequent manipulations. See ISO 6887-4 for
detailed requirements for the different types of low moisture products.
See ISO 6887-4 for further information on preparation of low-moisture products before testing for
specific groups of microorganisms, such as yeasts and moulds.
8.5 Liquid and non-viscous products
Before taking the test portion, the laboratory sample should be shaken by hand (e.g. 25 times through
an arc of 25 cm) or by mechanical means in order to ensure that the microorganisms are uniformly
distributed.
8.6 Acidic products
It is important when preparing a suspension of acidic products that the pH is brought back to near
neutrality (pH 7,0 ± 0,5).
The use of buffered peptone water (5.2.2) is sufficient for most products with pH greater than or equal
to 4,5. More acidic products (greater than or equal to pH 3,5) may be brought back to the required pH
using double-strength buffered peptone water (5.2.3), but the pH of such products should be checked
when these are tested for the first time to ensure the required range is achieved.
8 © ISO 2017 – All rights reserved

ISO 6887-1:2017(E)
Samples which continue to acidify during incubation of non-selective (pre-)enrichment cultures, e.g.
“live” yogurts and similar cultured products, may reduce the culture pH during incubation and should
be monitored to check the pH remains above 4,5. Increased buffering capacity may be used, but the
modified (pre-)enrichment of such products shall be verified to ensure conditions are satisfactory for
growth of the specific microorganisms sought.
See ISO 6887-4 for further information on preparation of acidic products before testing for specific
groups of microorganisms such as acidophiles.
8.7 High-fat (over 20 %) foods
The use of a diluent with between 1 g/l and 10 g/l of added polysorbate 80 [polyoxyethylene (20)
sorbitan monooleate], according to approximate fat levels, may improve emulsification during
suspension.
Generally, 1 g/l per 10 % fat content is sufficient (e.g. for fat content of 40 %, add 4 g/l).
See ISO 6887-4 for further information on examining high-fat foods.
8.8 Multi-component products
For multi-component products (which contain pieces of different foods), sampling should be carried out
by taking amounts of each component representative of their proportions in the initial product.
Homogenizing the whole laboratory sample is also possible as this will provide a more homogeneous
test sample for subsequent examination of a test portion (see Annex C).
It may be necessary to mince or to grind the laboratory sample. In this case, do not mince or grind for
more than 1 min to avoid an excessive rise in temperature.
8.9 Packaged products
Packaged products submitted to the laboratory are of various types but these are considered under
two headings as follows:
— soft packaging: to be removed or opened aseptically using scissors, knives or scalpels (6.9);
— rigid packaging (cans, glass containers, etc.) to be opened using appropriate implements (6.10)
under aseptic conditions.
All operations, before and after opening packaged foods, shall be carried out aseptically to avoid
external contamination.
If it is possible to remove the contents aseptically after opening without risk of external contamination,
cleaning and disinfecting of the packaging is not necessary.
Clean the surface of rigid or semi-rigid packaging using mild detergent in water, then dry with a clean
towel or fresh absorbent paper. When packaging is very thin and could be damaged by wetting (e.g.
pieces of food packaged in films or flexible containers), omit this step and disinfect only.
Disinfect the outside of packaging carefully with 70 % (volume fraction) alcohol or aseptic wipes to
avoid contamination when opening.
Open film-wrapped portions of food on trays carefully by peeling off the packaging film so the food can
be exposed for sampling.
For foods packed in a controlled atmosphere and vacuum-packed foods, open the sealed packaging
using a sterile knife, scalpel or scissors and forceps or tongs (6.9).
ISO 6887-1:2017(E)
8.10 Surface samples (swabs and other devices)
Mix the swabs, or other devices such as small cloths or wipes, in the same diluent as that used to
saturate them for sampling and/or to transport them, to disperse the microorganisms that adhere (see
ISO 18593).
To achieve this, break the handles off the swabs so the swabs may be shaken in the specified quantity
of diluent for the initial suspension. Small glass beads or balls (6.14) may be used to aid dispersion of
retained organisms on the swabs or other devices.
Use the resulting suspension as the initial suspension.
For surface samples, the init
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