Animal and vegetable fats and oils - Gas chromatography of fatty acid methyl esters - Part 2: Preparation of methyl esters of fatty acids (ISO 12966-2:2017)

ISO 12966-4:2015 specifies a method for the determination of fatty acid methyl esters (FAMEs) derived by transesterification or esterification from fats, oils, and fatty acids by capillary gas chromatography (GLC). Fatty acid methyl esters from C8 to C24 can be separated using this part of ISO 12966 including saturated fatty acid methyl esters, cis- and trans-monounsaturated fatty acid methyl esters, and cis- and trans-polyunsaturated fatty acid methyl esters.
The method is applicable to crude, refined, partially hydrogenated, or fully hydrogenated fats, oils, and fatty acids derived from animal and vegetable sources.
This method is not suitable for the analysis of dairy, ruminant fats and oils, or products supplemented with conjugated linoleic acid (CLA). Milk and milk products (or fat coming from milk and milk products) are excluded from the scope of this part of ISO 12966.
ISO 12966-4:2015 is not applicable to di-, tri-, polymerized and oxidized fatty acids, and fats and oils.

Tierische und pflanzliche Fette und Öle - Gaschromatographie von Fettsäuremethylestern - Teil 2: Herstellung von Fettsäuremethylestern (ISO 12966-2:2017)

Corps gras d'origines animale et végétale - Chromatographie en phase gazeuse des esters méthyliques d'acides gras - Partie 2: Préparation des esters méthyliques d'acides gras (ISO 12966-2:2017)

ISO 12966-4:2015 spécifie une méthode de détermination des esters méthyliques d'acides gras (EMAG) obtenus par transestérification ou estérification de corps gras et d'acide gras par chromatographie en phase gazeuse (CPG) sur colonne capillaire. Les esters méthyliques d'acides gras de C8 à C24 peuvent être séparés en utilisant la présente partie de l'ISO 12966, y compris les esters méthyliques d'acides gras saturés, les esters méthyliques d'acides gras mono-insaturés cis et trans et les esters méthyliques d'acides gras poly-insaturés cis et trans.
La méthode s'applique aux corps gras et acides gras bruts, raffinés, partiellement hydrogénés ou totalement hydrogénés d'origines animale et végétale.
La présente méthode ne convient pas à l'analyse des matières grasses laitières provenant des ruminants, ou des produits supplémentés en acide linoléique conjugué (CLA). Le lait et les produits laitiers (ou corps gras dérivés du lait et des produits laitiers) ne relèvent pas du domaine d'application de la présente partie de l'ISO 12966.
ISO 12966-4:2015 ne s'applique pas aux acides gras et corps gras dimérisés, trimérisés, polymérisés et oxydés.

Rastlinske in živalske maščobe in olja - Plinska kromatografija metilnih estrov maščobnih kislin - 2. del: Priprava metilnih estrov maščobnih kislin (ISO 12966-2:2017)

Ta del standarda ISO 12966-4:2015 določa metodo za določanje metilnih estrov maščobnih kislin (FAME), pridobljenih s transesterifikacijo ali esterifikacijo iz maščob, olj in maščobnih kislin, s kapilarno plinsko kromatografijo (GLC). Metilne estre maščobnih kislin C8 do C24 je mogoče ločiti z uporabo metode iz tega dela standarda ISO 12966, vključno z metilnimi estri nasičenih maščobnih kislin, metilnimi estri cis- in trans-enkratno nenasičenih maščobnih kislin ter metilnimi estri cis- in trans-večkratno nenasičenih maščobnih kislin.
Ta metoda velja za surove, rafinirane in delno ali povsem hidrogenirane maščobe, olja in maščobne kisline, pridobljene iz živalskih in rastlinskih virov.
Ta metoda ni primerna za analizo mlečnih izdelkov, maščob in olj prežvekovalcev ali izdelkov z dodano konjugirano linolno kislino (CLA). Mleko in mlečni izdelki (ali maščoba iz mleka in mlečnih izdelkov) niso zajeti v tem delu standarda ISO 12966.
Standard 12966-4:2015 se ne uporablja za dimerne, trimerne, polimerne in oksidirane maščobne kisline ter maščobe in olja.

General Information

Status
Published
Public Enquiry End Date
19-Feb-2017
Publication Date
05-Jun-2017
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
05-May-2017
Due Date
10-Jul-2017
Completion Date
06-Jun-2017

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SLOVENSKI STANDARD
SIST EN ISO 12966-2:2017
01-julij-2017
1DGRPHãþD
SIST EN ISO 12966-2:2011
5DVWOLQVNHLQåLYDOVNHPDãþREHLQROMD3OLQVNDNURPDWRJUDILMDPHWLOQLKHVWURY
PDãþREQLKNLVOLQGHO3ULSUDYDPHWLOQLKHVWURYPDãþREQLKNLVOLQ ,62


Animal and vegetable fats and oils - Gas chromatography of fatty acid methyl esters -

Part 2: Preparation of methyl esters of fatty acids (ISO 12966-2:2017)
Tierische und pflanzliche Fette und Öle - Gaschromatographie von

Fettsäuremethylestern - Teil 2: Herstellung von Fettsäuremethylestern (ISO 12966-

2:2017)
Corps gras d'origines animale et végétale - Chromatographie en phase gazeuse des

esters méthyliques d'acides gras - Partie 2: Préparation des esters méthyliques d'acides

gras (ISO 12966-2:2017)
Ta slovenski standard je istoveten z: EN ISO 12966-2:2017
ICS:
67.200.10 5DVWOLQVNHLQåLYDOVNH Animal and vegetable fats
PDãþREHLQROMD and oils
71.040.50 Fizikalnokemijske analitske Physicochemical methods of
metode analysis
SIST EN ISO 12966-2:2017 de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN ISO 12966-2:2017
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SIST EN ISO 12966-2:2017
EN ISO 12966-2
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2017
EUROPÄISCHE NORM
ICS 67.200.10 Supersedes EN ISO 12966-2:2011
English Version
Animal and vegetable fats and oils - Gas chromatography
of fatty acid methyl esters - Part 2: Preparation of methyl
esters of fatty acids (ISO 12966-2:2017)

Corps gras d'origines animale et végétale - Tierische und pflanzliche Fette und Öle -

Chromatographie en phase gazeuse des esters Gaschromatographie von Fettsäuremethylestern - Teil

méthyliques d'acides gras - Partie 2: Préparation des 2: Herstellung von Fettsäuremethylestern (ISO 12966-

esters méthyliques d'acides gras (ISO 12966-2:2017) 2:2017)
This European Standard was approved by CEN on 3 April 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 12966-2:2017 E

worldwide for CEN national Members.
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SIST EN ISO 12966-2:2017
EN ISO 12966-2:2017 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 12966-2:2017
EN ISO 12966-2:2017 (E)
European foreword

This document (EN ISO 12966-2:2017) has been prepared by Technical Committee ISO/TC 34 “Food

products” in collaboration with Technical Committee CEN/TC 307 “Oilseeds, vegetable and animal fats

and oils and their by-products - Methods of sampling and analysis” the secretariat of which is held by

AFNOR.

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 12966-2:2011.

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 12966-2:2017 has been approved by CEN as EN ISO 12966-2:2017 without any

modification.
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SIST EN ISO 12966-2:2017
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SIST EN ISO 12966-2:2017
INTERNATIONAL ISO
STANDARD 12966-2
Second edition
2017-03
Animal and vegetable fats and oils —
Gas chromatography of fatty acid
methyl esters —
Part 2:
Preparation of methyl esters of fatty
acids
Corps gras d’origines animale et végétale — Chromatographie en
phase gazeuse des esters méthyliques d’acides gras —
Partie 2: Préparation des esters méthyliques d’acides gras
Reference number
ISO 12966-2:2017(E)
ISO 2017
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SIST EN ISO 12966-2:2017
ISO 12966-2:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© 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

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
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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
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SIST EN ISO 12966-2:2017
ISO 12966-2:2017(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Reactions ...................................................................................................................................................................................................................... 1

5 Methodology ............................................................................................................................................................................................................. 2

5.1 Preparation of test sample ............................................................................................................................................................ 2

5.2 Rapid method ........................................................................................................................................................................................... 2

5.2.1 Applicability ......................................................................................................................................................................... 2

5.2.2 Principle .................................................................................................................................................................................. 2

5.2.3 Reagents .................................................................................................................................................................................. 3

5.2.4 Apparatus ............................................................................................................................................................................... 3

5.2.5 Procedure ............................................................................................................................................................................... 3

5.3 General method ...................................................................................................................................................................................... 4

5.3.1 Applicability ......................................................................................................................................................................... 4

5.3.2 Principle .................................................................................................................................................................................. 4

5.3.3 Reagents .................................................................................................................................................................................. 4

5.3.4 Apparatus and materials ........................................................................................................................................... 5

5.3.5 Procedure ............................................................................................................................................................................... 5

5.4 Transmethylation using boron trifluoride (BF ) catalyst .................................................................................. 6

5.4.1 Principle .................................................................................................................................................................................. 6

5.4.2 Applicability ......................................................................................................................................................................... 6

5.4.3 Reagents .................................................................................................................................................................................. 6

5.4.4 Apparatus ............................................................................................................................................................................... 7

5.4.5 Procedure ............................................................................................................................................................................... 8

5.5 Acid-catalysed transmethylation of glycerides ........................................................................................................... 9

5.5.1 Principle .................................................................................................................................................................................. 9

5.5.2 Reagents .................................................................................................................................................................................. 9

5.5.3 Apparatus ............................................................................................................................................................................10

5.5.4 Preparation of test sample ...................................................................................................................................10

5.5.5 Procedure ............................................................................................................................................................................10

Annex A (informative) Thin-layer chromatography method for testing the completeness

of derivatization .................................................................................................................................................................................................11

Bibliography .............................................................................................................................................................................................................................15

© ISO 2017 – All rights reserved iii
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SIST EN ISO 12966-2:2017
ISO 12966-2:2017(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 voluntary nature of standards, 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: w w w . i s o .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 11,

Animal and vegetable fats and oils.

This second edition cancels and replaces the first edition (ISO 12966-2:2011), of which it constitutes a

minor revision.
The changes compared to the previous edition are as follows:
— milk and milk fat products have been excluded from the scope.
A list of all the parts in the ISO 12966 series can be found on the ISO website.
iv © ISO 2017 – All rights reserved
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SIST EN ISO 12966-2:2017
ISO 12966-2:2017(E)
Introduction
General

Oils and fats (i.e. liquid and solid lipids) are predominantly composed of fatty acid esters of glycerol

(triacylglycerols, TAGs), with smaller amounts of fatty acid esters of sterols and long chain of aliphatic

alcohols. Due to the high molecular mass of the TAGs and their consequent low volatility, they are

difficult to analyse directly by gas chromatography (GC), especially if a detailed analysis of unsaturated

fatty acids is required. Fatty acids themselves do not chromatograph well (except for short-chain-length

fatty acids, e.g. butanoic and pentanoic acids). It is therefore better practice to form fatty acid esters,

usually the fatty acid methyl esters (FAMEs), prior to GC.
The analysis of oils and fats has been extensively reviewed in Reference [9].

The formation of FAMEs is a critical stage in the analysis of fatty acids. Non-quantitative conversion

of fatty acids to FAMEs, modification of the structure of fatty acids (e.g. changes in positional and

geometric isomers present) and formation of non-FAME artefacts may all affect the quantitative

determination of fatty acid composition.

Transesterification is one mechanism which can be employed to form FAMEs from fatty acid esters in

fats (i.e. triacylglycerol). Alkali- or acid-catalysed transesterification procedures can be used to form

FAMEs in a methanolic medium; the procedure can be termed transmethylation. Transmethylation is

a reversible process and a large excess of methanol is required to maintain an equilibrium position

which favours formation of the FAMEs. Water can prevent the reaction going to completion, and its

presence should therefore be minimized. Alkali-catalysed procedures do not produce FAMEs from free

fatty acids, due to the formation of soaps.

Esterification is an acid-catalysed mechanism which can be employed to form FAMEs from fatty acids.

It is possible that the fatty acids are naturally present in the sample of fat under examination. Formation

of FAMEs by this mechanism is commonly termed methylation. Again, an excess of methanol and the

absence of water are preconditions for the quantitative formation of FAMEs.

This document provides guidelines for the preparation of fatty acid methyl esters. In support of these

guidelines, various procedures to prepare fatty acid methyl esters are specified. These include the

following:
a) “rapid” transmethylation under alkaline conditions;

b) “general” transmethylation/methylation under sequential alkaline and acid conditions;

c) boron trifluoride (BF ) transmethylation/methylation.
“Rapid” transmethylation method under alkali-catalysed conditions

This method is applicable to the routine analysis of edible fats and oils containing fatty acids down to

butanoic acid (C4:0) and/or for the determination of butanoic acid or hexanoic acid (C6:0) by GC using

an internal standard.

Alkaline catalysts transesterify neutral lipids in the presence of anhydrous methanol (transmethylation)

more rapidly than acid catalysts. The disadvantages of such alkali-catalysed procedures are that free

fatty acids are not esterified, and the presence of water may prevent the transmethylation going to

completion (hydrolysis of the FAMEs to free fatty acids). The most commonly used reagents are

potassium and sodium hydroxide and sodium methoxide in the presence of anhydrous methanol.

“General” transmethylation/methylation under sequential alkaline and acid conditions

This method under sequential alkali- and acid-catalysed conditions is applicable to all oils and fats

including distillate and acid oils, but is not recommended for lauric oils. Short-chain fatty acid methyl

esters are easily lost during reflux. For lauric acid oils, the “rapid” transmethylation method is

recommended.
© ISO 2017 – All rights reserved v
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SIST EN ISO 12966-2:2017
ISO 12966-2:2017(E)

During methylation, substances containing the following configurations can be totally or partially

decomposed:
a) keto, epoxy, hydroxyl, hydroperoxy groups;
b) cyclopropyl and cyclopropenyl groups;
c) acetylenic fatty acids.
Boron trifluoride (BF ) transmethylation/methylation

Owing to the toxicity of BF it is recommended that this method only be used in extremis.

The BF method is applicable for most oils, fats and derivatives (fatty acids, soaps) with the exception of

milk fats and fats containing fatty acids with specific groups.

During methylation, substances containing the following configurations can be totally or partially

decomposed:
a) keto, epoxy, hydroxyl, hydroperoxy groups;
b) cyclopropyl and cyclopropenyl groups;
c) acetylenic fatty acids.

If the fatty matter contains such substances in only very small amounts (e.g. cottonseed oil), the method

can be applied; otherwise, the “rapid” or “general” transmethylation/methylation methods should be

followed.

For GC, the optimum recovery of the methyl esters from the reaction mixture is obtained by using

isooctane (2,2,4-trimethylpentane). However, only about 75 % of the methyl caproate present is

recovered.

Boron trifluoride is a strong Lewis acid, and in the form of its coordination complex with methanol, under

reflux conditions, it can rapidly methylate fatty acids. Methanolic boron trifluoride does transmethylate

fatty acid esters (e.g. triglyceride), but the rate of reaction is slower than the methylation of fatty acids.

Methanolic boron trifluoride solution is commercially available, which enhances the attractiveness of

this acid catalyst, but there are potential disadvantages associated with the use of this reagent.

a) It has been reported that high concentrations of boron trifluoride (50 % mass fraction) produce

methoxy artefacts from unsaturated fatty acids.

b) The reagent has a limited shelf-life at ambient temperature and should be kept refrigerated.

c) Aged reagent can produce artefacts and therefore, it is recommended that each new batch

purchased be tested before use and periodically during its lifetime.

d) Methanolic boron trifluoride is an acidic reagent and therefore can produce derivatives of fatty

acids containing labile groups which can give rise to spurious peaks on FAME chromatograms.

Additional information

Much attention has been given to the preparation and analysis of esters of short-chain fatty acids by GC,

largely because of their occurrence in milk fats. Short-chain fatty acids, in the free state or esterified to

glycerol, can be converted completely to methyl esters by any of the reagents described in the preceding

paragraphs, but quantitative recovery from the reaction medium may not be achieved unless special

precautions are taken. Losses can occur at several stages in any procedure. Short-chain fatty acid esters

(methyl especially) are volatile and may be lost selectively on refluxing the esterification medium;

they are more soluble in water than longer-chain esters and can be lost in an aqueous extraction step

or they may be distilled off when the extracting solvent is evaporated. Selective losses can also occur

if non-saponifiable impurities have to be removed by sublimation or thin-layer chromatography (TLC)

purification. The best esterification procedures for short-chain fatty acids are those in which heating of

the reagents is avoided and in which stages involving aqueous extraction and solvent removal are absent.

vi © ISO 2017 – All rights reserved
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SIST EN ISO 12966-2:2017
ISO 12966-2:2017(E)

Injection of reaction media containing basic and acidic esterification catalysts directly on to GC

columns shortens their working lives. The top few centimetres of packed columns can be replenished

periodically, while lengths of deactivated tubing or “retention gaps” ahead of capillary columns protect

them. This can be a small price to pay for the speed, simplicity and accuracy of these procedures.

Additionally, this document gives a simple TLC procedure to check the effectiveness of the

transmethylation/methylation. This procedure may also be used to check the generic composition of an

oil or fat before transmethylation/methylation is undertaken.
© ISO 2017 – All rights reserved vii
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SIST EN ISO 12966-2:2017
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SIST EN ISO 12966-2:2017
INTERNATIONAL STANDARD ISO 12966-2:2017(E)
Animal and vegetable fats and oils — Gas chromatography
of fatty acid methyl esters —
Part 2:
Preparation of methyl esters of fatty acids
1 Scope
This document specifies methods of preparing the methyl esters of fatty acids.

It includes methods for preparing fatty acid methyl esters from animal and vegetable fats and oils, fatty

acids and soaps. To cover different requirements, four methylation methods are specified, namely:

a) a “rapid” transmethylation procedure under alkaline conditions;

b) a “general” transmethylation/methylation procedure under sequential alkaline and acid conditions;

c) a BF transmethylation procedure;
d) an alternative procedure using acid-catalysed transmethylation of glycerides.

Methyl esters so produced are used in various analytical procedures requiring such derivatives, e.g.

gas-liquid chromatography (GLC), thin-layer chromatography (TLC) and infrared spectrometry (IR).

Milk and milk products (or fat coming from milk and milk products) are excluded from the scope of this

document.
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 661, Animal and vegetable fats and oils — Preparation of test sample
3 Terms and definitions
No terms and definitions are listed in this document.

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
4 Reactions

The determination of the fatty acid composition of oils and fats is one of the fundamental analyses

within the fats and oils sector and has been extensively reviewed in Reference [9]. For this purpose, the

fatty acid components of lipids are usually converted to methyl esters followed by GC analysis.

The “rapid” method (5.2) does not derivatize free fatty acids (FFAs) present in oil to fatty acid methyl

esters (FAMEs). If FFAs are present, the assumption is usually made that the FFAs have the same fatty

© ISO 2017 – All rights reserved 1
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SIST EN ISO 12966-2:2017
ISO 12966-2:2017(E)

acid distribution as the triglycerides. This is usually true for crude oils, but less so for fractionated or

refined oils. Except for some cold-pressed oils, as a general rule, oils with <0,5 % mass fraction FFAs

have probably been refined; oils above can be assumed to be crude. The tolerable concentration of FFAs

in oil depends on the particular oil being analysed and also the intended use of the FAME data generated.

The presence of FFAs in oil might introduce additional peaks on the final gas chromatogram and make

the identification of FAMEs synthesized using the “rapid” transmethylation procedure problematic.

The “general” (5.3) procedure derivatizes both FFAs and glyceryl esters to FAMEs (see 5.3.1).

It is up to the analyst to decide whether the use of either the “rapid” or “general” procedure is

appropriate based on the nature of the oil being analysed. This notwithstanding, as a general rule,

use of the “rapid” method is suggested only if the FFA content is ≤0,5 % mass fraction. The “general”

method (5.3) is suggested for oils with an FFA content >0,5 % mass fraction. Alternatively, if a partially

hydrolysed fat is to be converted to FAMEs, the acid-catalysed transmethylation procedure specified in

5.5 may be used.

Owing to the toxicity of BF , it is recommended that the BF method (5.4) be used only in extremis.

3 3
5 Methodology

WARNING — The method specified involves the use of potentially hazardous reagents. Normal

precautions shall be taken for eye protection and for protection from the dangers of corrosive

chemical burns. Methanolic potassium hydroxide solution is poisonous.
5.1 Preparation of test sample

The test sample shall be liquid, dry and clear. Proceed in accordance with ISO 661, but heat the sample

to just above the melting point.
5.2 Rapid method
5.2.1 Applicability

This rapid transmethylation method, under alkali-catalysed conditions, is applicable to the routine

analysis of edible fats and oils containing fatty acids down to butanoic acid (C4:0) and/or for the

determination of butanoic acid or hexanoic acid (C6:0) by GC using an internal standard.

This procedure does not derivatize FFAs to FAMEs. The analyst should note that the presence of FFAs in

the final solution can affect the quality of subsequent gas chromatography.
[8]

NOTE According to COI/T.20/Doc. No. 24:2001 , a similar procedure can be applied directly to samples of

the following oil categories:
a) virgin olive oil with an acidity less than 3,3 %;
b) refined olive oil;
c) olive oil (blend of virgin and refined olive oil);
d) refined olive-pomace oil;
e) olive-pom
...

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