ISO 4134:2021

INTERNATIONAL ISO
STANDARD 4134
Third edition
2021-07
Meat and meat products —
Determination of L-(+)-glutamic acid
content — Reference method
Viande et produits à base de viande — Détermination de la teneur en
acide L-(+)-glutamique — Méthode de référence
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Sampling . 2
6 Preparation of test sample . 2
7 Test method of spectrophotometer . 2
7.1 Reagents. 2
7.2 Apparatus . 4
7.3 Procedure . 5
7.3.1 General. 5
7.3.2 Test portion . 5
7.3.3 Preparation of extract . . 5
7.3.4 Determination . 5
7.4 Calculation and results . 6
7.4.1 Absorbance difference of L-(+)-glutamic acid standard solution . 6
7.4.2 Absorbance difference of L-(+)-glutamic acid test solution . 7
7.4.3 Formula of linear regression of L-(+)-glutamic acid standard curve . 7
7.4.4 L-(+)-glutamic acid concentration of the test solution . 7
7.4.5 L-(+)-glutamic acid content of test sample . 8
7.5 Precision . 8
7.5.1 Interlaboratory test . 8
7.5.2 Repeatability . 8
7.5.3 Reproducibility . 8
7.6 Detection limit . 8
8 Test method of light absorption microplate reader . 9
8.1 Reagents. 9
8.2 Apparatus . 9
8.3 Procedure . 9
8.3.1 General. 9
8.3.2 Extraction of L-(+)-glutamic acid in the test portion . 9
8.3.3 Determination . 9
8.4 Calculation and results .10
8.4.1 Absorbance difference for L-(+)-glutamic acid standard solution .10
8.4.2 Absorbance difference for L-(+)-glutamic acid test solution.10
8.4.3 Formula of linear regression for L-(+)-glutamic acid standard curve .11
8.4.4 L-(+)-glutamic acid concentration of the test solution .11
8.4.5 L-(+)-glutamic acid content of test sample .11
8.5 Precision .12
8.5.1 Interlaboratory test .12
8.5.2 Repeatability .12
8.5.3 Reproducibility .12
8.6 Detection limit .12
9 Test report .12
Annex A (informative) Safety practices .14
Bibliography .15
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
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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.
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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 www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 6,
Meat, poultry, fish, eggs and their products.
This third edition cancels and replaces the second edition (ISO 4134:1999), which has been technically
revised. The main changes compared with the previous edition are as follows:
— a new test method, the light absorption microplate reader method, has been added;
— the order of the clauses has been rearranged;
— the Scope (Clause 1) has been revised to specify free L-(+)-glutamic acid in meat and meat products;
— the Normative references (Clause 2) have been updated;
— the Terms and definitions (Clause 3) have been modified by adding the term “free L-(+)-glutamic
acid”;
— in Clause 4, the description of “extraction of L-(+)-glutamic acid of test portion” has been modified
and the detection wavelength has been changed from “492 nm” to “490 nm”;
— in 7.1, the identification of enzyme activity units for diaphorase and glutamate dehydrogenase has
been supplemented; the concentration of KOH, NAD has been modified; the NAD and diaphorase
have been mixed into a solution; and the buffer, NAD and enzymes have been labelled with R1, R2,
and R3;
— the apparatus list (7.2) has been updated;
— in 7.3, the procedure of the test method of spectrophotometer has been modified by halving the
sample mass and solution volume;
— in 7.3.4, the method of judging the absorbance of the reaction end point has been modified and, as a
result, the previous Annex B “Example of plotting and extrapolation of absorbance values” has been
deleted;
iv © ISO 2021 – All rights reserved

— in 8.4, the formula and symbol description of spectrophotometer has been modified;
— the previous Annex C “Derivation of equation for calculation of L-(+)-glutamic acid content” has
been deleted;
— the Bibliography has been updated.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
INTERNATIONAL STANDARD ISO 4134:2021(E)
Meat and meat products — Determination of L-(+)-
glutamic acid content — Reference method
1 Scope
This document specifies the spectrophotometer method and the light absorption microplate reader
method for the determination of the free L-(+)-glutamic acid content of meat and meat products.
This document is applicable to meat and meat products, including livestock and poultry products.
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 648, Laboratory glassware — Single-volume pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 1442, Meat and meat products — Determination of moisture content (Ref
...