UGANDA STANDARD  
     US ISO 6498
First Edition
  2009 -09-04
 
Reference numbe r 
  US ISO 6498:1998
 © UNBS 200 9 
  
Animal feeding stuffs — Preparation of test samples 
 US ISO 6498:1998  
 
© UNBS  2009 – All rights reserved Compliance with this standard does not, of itself confer immunity from legal obligations 
A Uganda Standard does not purport to include all necessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS 2009  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilised in any 
form or by any means, electronic or mechanical, in cluding photocopying and microfilm, without prior written 
permission from UNBS. 
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Tel: 256 41 505 995 
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     US ISO 6498:1998  
© UNBS  2009 - All rights reserved National foreword 
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry  of Tourism, Trade and 
Industry established by the Act of Parliament of 198 3, of the Laws of Uganda.  UNBS is mandated to co-
ordinate the elaboration of standards and is  
(a) a member of International Organisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex A limentarius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT/SPS Agr eements of the World Trade Organisation (WTO). 
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a gi ven field or area and consists of representatives of 
consumers, traders, academician s, manufacturers, governme nt and other stakeholders. 
Draft Uganda Standards adopted by the Technical Committ ee are widely circulated to stakeholders and the 
general public for comments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council. 
This Uganda Standard, US ISO 6498:1998,  Animal feeding stuffs — Preparation of test samples, is identical 
with and  has been reproduced from an International Standard ISO 6498:1998,  Animal feeding stuffs — 
Preparation of test samples, and has been adopted  as a Uganda Standard . 
Wherever the words, "International Standard" a ppear, they should be replaced by "Uganda Standard." A Reference numbe r
ISO 6498:1998 (E)INTERNATIONAL
STANDARDISO
6498
Second edition
1998-11-01
Animal feeding stuffs — Preparation of test
samples
Aliments des animaux — Préparation des échantillons pour essaiISO 6498:1998(E)
©   ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying andmicrofilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
iiForeword
ISO (the International Organization for Standardization) is a worldwide
federation of national standards bodies (ISO member bodies). The work ofpreparing International Standards is normally carried out through ISOtechnical committees. Each member body interested in a subject for whicha technical committee has been established has the right to be representedon that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISOcollaborates closely with the International Electrotechnical Commission(IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in
the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an InternationalStandard requires approval by at least 75 % of the member bodies castinga vote.
International Standard ISO 6498 was prepared by Technical Committee
ISO/TC 34, 
Agricultural food products , Subcommittee SC 10, Animal
feeding stuffs.
This second edition cancels and replaces the first edition (ISO 6498:1983),which has been technically revised.
Annex A of this International Standard is for information only.INTERNATIONAL STANDARD    © ISO ISO 6498:1998(E)
1Animal feeding stuffs — Preparation of test samples
1 Scope
This International Standard specifies methods for the preparation of test samples from laboratory samples of animal
feeding stuffs including pet foods.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions ofthis International Standard. For dated references, subsequent amendments to, or revisions of, any of thesepublications do not apply. However, parties to agreements based on this International Standard are encouraged toinvestigate the possibility of applying the most recent editions of the normative documents indicated below. Forundated references, the latest edition of the normative document referred to applies. Members of ISO and IECmaintain registers of currently valid International Standards.
ISO 6492, 
Animal feeding stuffs — Determination of fat content.
ISO 6496, Animal feeding stuffs — Determination of moisture content.
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
3.1
laboratory sample
sample representative of the quality and condition of the lot, obtained by reduction of the bulk sample and intended
for analysis or other examination
3.2
test sample
representative portion of the laboratory sample, obtained by dividing by means of a sample divider or by hand, if
necessary after reduction of the particle size
3.3
test portion
representative portion of the test sample or laboratory sample
4 Principle
For solids, the laboratory sample is thoroughly mixed and divided successively using a specified procedure until a
test sample of a suitable size is obtained. A process of crushing, grinding, mincing or homogenizing is used, whereappropriate, to ensure that the test sample, from which the test portion(s) will be taken, truly represents thelaboratory sample. In the case of a fluid feeding stuff, the laboratory sample is mixed mechanically and arepresentative test sample is obtained while the fluid is agitated.ISO 6498:1998(E) © ISO
25 Apparatus
5.1   Mechanical mill , easy to clean and capable of grinding feeding stuffs without generation of excessive heat
and without causing appreciable change in moisture, until the sample passes completely through a sieve ofappropriate aperture size (5.5).
A few feeding stuffs are likely to lose or gain moisture. In these cases, it is necessary to apply a correction factor to
the results (see 7.2 and clause 8).
NOTE  The screen size in the mill is not necessarily the same as the sieve size for checking the extent of grinding.
5.2   Mechanical stirrer  or homogenizer
5.3   Mincer, fitted with a 4 mm plate.
5.4   Crushing apparatus , for example, a pestle and mortar.
5.5   Sieves, of aperture sizes 1,00 mm, 2,80 mm and 4,00 mm, made from woven metal wire cloth.
5.6   Dividing or quartering apparatus , such as a conical divider (see Figure A.1), multiple-slot divider with a
sorting system (see Figure A.2), or other dividing apparatus that w ill ensure uniform distribution of the components
of the laboratory sample in the test sample.
5.7   Sample container , suitable for protecting the test sample from change in composition, and from the effect of
light, and of such a size that it will be almost completely filled by the test sample.
It is essential that the container can be securely closed.
6 Sampling
Sampling is not part of the method specified in this International Standard. A recommended sampling method is
given in ISO 6497 [1].
It is important that the laboratory receive a sample which is truly representative and has not been damaged or
changed during transport or storage.
Store the sample in such a way that deterioration and change in composition are minimized.
7 Procedure
WARNING: It is emphasized that care is to be taken to ensure that the apparatus is not a source of
contamination.
7.1 Grinding
7.1.1 General
Grinding of some samples may lead to a loss or gain of moisture and, if appropriate, allowance for this should be
made (see 7.2 and clause 8). Grinding should be as rapid as possible and exposure to the atmosphere should beminimized. If necessary, first break or crush the pieces to a suitable size for grinding. It is essential that the samplebe thoroughly mixed before each stage of the procedure.
7.1.2 Fine samples
If the laboratory sample passes the 1,00 mm sieve (5.5) completely, mix it thoroughly. Divide the mixture
successively using the dividing or quartering apparatus (5.6) until a test sample of suitable size is obtained(see 7.9).© ISO ISO 6498:1998(E)
37.1.3 Coarse samples
7.1.3.1If the laboratory sample does not pass the 1,00 mm sieve (5.5) completely, but passes the 2,80 mm sieve
completely, mix it thoroughly and prepare a sample of suitable size (see 7.9) by successive divisions as in 7.1.2.
7.1.3.2Carefully grind this sample in the well-cleaned mill (5.1) as in 7.1.1, until it passes through the 1,00 mm
sieve completely.
7.1.4 Coarser samples
7.1.4.1   If the laboratory sample does not pass completely through the 2,80 mm sieve (5.5), carefully  grind it in the
well-cleaned mill (5.1) until it passes the 2,80 mm sieve completely. Mix it thoroughly.
7.1.4.2   Divide the ground laboratory sample successively by means of the  dividing apparatus (5.6) until a test
sample of suitable size (see 7.9) for all the determinations required is obtained. Grind this sample in the well-cleaned mill (5.1) until it passes the 1,00 mm sieve (5.5) completely.
7.2 Samples likely to lose or gain moisture
If grinding operations are likely to result in loss or gain of moisture, determine the moisture content by the methoddescribed in ISO 6496. Apply the method to the well-mixed laboratory sample as received and to the prepared testsample, so that the results of analyses may be corrected to relate to the sample in its original condition as regardsmoisture content (see clause 8).
7.3 Samples difficult to grind
If the condition of a laboratory sample not passing through the 1,00 mm sieve (5.5) makes grinding difficult, take aportion immediately after the preliminary mixing described in 7.1.3.1, or after the preliminary grinding proceduredescribed in 7.1.4.1.
Determine the moisture content by the method described in ISO 6496. Dry the sample until, after crushing with the
pestle and mortar (5.4) or by other means, it passes the 1,00 mm sieve completely. Again determine the moisturecontent of the prepared test sample so that the results of analyses may be corrected to relate to the sample in itsoriginal condition as regards moisture content (see clause 8).
7.4 Moist feeding stuffs such as canned or chilled pet foods
Homogenize the laboratory sample (which may be the entire contents of a can or other package) using themechanical stirrer or homogenizer (5.2). Thoroughly mix the homogenized sample. Fill a clean, dry samplecontainer (5.7) and close tightly. Take test portions as soon as possible, preferably immediately. Otherwise store
the test sample at between 0 °C and 4 °C.
7.5 Frozen feeding stuffs
Cut or break the laboratory sample into small pieces with a suitable implement. Immediately pass the pieces
through the mincer (5.3). Mix the minced sample until any liquid that has separated out is thoroughly re-dispersedthroughout the sample. Fill a clean, dry sample container (5.7) and close tightly. Take test portions as soon as
possible, preferably immediately, storing the test sample at between 0 °C and 4 °C.
7.6 Feeding stuffs of intermediate moisture content
Slowly pass the laboratory sample through the mincer (5.3). Thoroughly mix the minced sample and immediately
pass it through a 4,00 mm sieve (5.5). Fill a clean, dry sample container (5.7) and close tightly.
If the nature of the laboratory sample is such that it cannot be minced, mix and grind it as well as possible by hand.ISO 6498:1998(E) © ISO
47.7 Silage and liquid samples
7.7.1 Grass or cereal silage
Pass the entire laboratory sample through the mechanical mill (5.1) if possible, or otherwise chop it as finely as
possible. Mix thoroughly and transfer a test sample of at least 100 g to a sample container (5.7).
If the laboratory sample cannot be passed through the mill or cannot be finely chopped, mix it as thoroughly as
possible and determine the moisture content by the method described in ISO 6496. Dry the laboratory sample (for
example, overnight at between 60 °C and 70 °C in an electrically heated oven, well ventilated) and then pass it
through the mechanical mill (5.1). Mix thoroughly and transfer a test sample of at least 100 g to a sample container
(5.7). Determine the moisture content of the prepared test sample by the method described in ISO 6496 and apply acorrection to all results (see clause 8).
7.7.2 Liquid samples including fish silage
Mix the laboratory sample using a mechanical stirrer or homogenizer (5.2), so that any separated material (ground
bone, oil, etc.) is completely dispersed. During agitation, transfer 50 ml to 100 ml to a sample container (5.7) using aladle, beaker or wide-bore pipette.
7.8 Samples for which there are special requirements
NOTE 1 Some determinations may require special preparation of the test samples. The specific procedures required are
described in the relevant section of the test method.
For determinations requiring special degrees of fineness, further grinding may be necessary. In such cases, prepare
another test sample as described in 7.1, 7.2 or 7.3, but having the required degree of fineness.
In some cases it may be necessary to avoid breaking or damaging the laboratory sample, for example, for the
determination of pellet hardness.
NOTE 2 If the laboratory sample is thought to be non-homogeneous, for example for analytes such as mycotoxins or
medicinal additives, it may be necessary to grind the whole of the sample and then reduce the sample size to produce asuitable test portion.
If the sample is fatty, the test sample may be prepared by warming and mixing. In some cases preliminary
extraction of fat may be necessary. This shall be carried out in accordance with ISO 6492.
If microbiological examination is required, the sample shall be handled under sterile conditions and in such a way
that the microbial condition does not change.
7.9 Size and storage of test samples
Prepare a sufficient test sample for all the determinations likely to be required and not less than 100 g. Completelyfill the chosen container (5.7) without delay and close it securely.
Store the test sample under such conditions that changes are reduced to a minimum, paying particular attention to
the avoidance of exposure to light and to the effect of temperature.
8 Correction factor
8.1 General
If there is likely to be a loss or gain of moisture during the grinding or mixing operations, it is necessary to use acorrection factor to relate the results of analyses to the sample in its original condition as regards moisture content.A similar concept applies if a preliminary extraction of fat is carried out.© ISO ISO 6498:1998(E)
58.2 Calculation
Calculate the correction factor f by the equation:
fw
w=-
-100
1000
1%
%
where
fis the correction factor;
w0is the mass fraction of moisture, expressed in percent, of the laboratory sample, determined by the method
described in ISO 6496;
w1is the mass fraction of moisture, expressed in percent, of the prepared test sample, determined by the
method described in ISO 6496.
8.3 Correction of results
Multiply the results of analyses by the correction factor f.ISO 6498:1998(E) © ISO
6Annex A
(informative)
Examples of dividing apparatus
Key
1 Hopper
2 Cut-off3 Spaces which open into outer funnel4 Ducts which spout into inner funnel5 Inner funnel6 Outer funnel
7 Receptacle8 Base of cone9 Peak of cone10 Ducts connected below base of cone
Figure A.1 — Conical divider© ISO ISO 6498:1998(E)
7
Figure A.2 — Multiple-slot divider with sorting systemISO 6498:1998(E) © ISO
8Bibliography
[1] ISO 6497, Animal feeding stuffs  — Sampling.ISO 6498:1998(E) © ISO
ICS  65.120
Descriptors:  agricultural products,  food,  animal feeding products,  test specimens,  specimen preparation.
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