EN ISO 21415-2:2026

• Abstract:

  This document specifies a method for determining the content of wet gluten and the gluten index for wheat flours (Triticum aestivum L. and Triticum durum Desf.) by mechanical means.; This document is directly applicable to flours. It is also applicable to common and durum wheat after grinding, if their particular size distribution meets the specification given in Table B.1.; NOTE This document is related to ICC 137/1[7], ICC 155[8] and AACC Method 38-12.02[9].

• Status: Published
• Publication Date: 02-Jun-2026
• ICS: 67.060 - Cereals, pulses and derived products
• Technical Committee: CEN/TC 338 - Cereal and cereal products
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 03-Jun-2026
• Completion Date: 03-Jun-2026
• Ref Project: SIST EN ISO 21415-2:2026 - Wheat and wheat flour - Gluten content - Part 2: Determination of wet gluten and gluten index by mechanical means (ISO 21415-2:2026)

• Replaces: EN ISO 21415-2:2015 - Wheat and wheat flour - Gluten content - Part 2: Determination of wet gluten and gluten index by mechanical means (ISO 21415-2:2015)
• Effective Date: 22-Jan-2025
• Consolidated By: ISO 21415-2:2026 - Wheat and wheat flour — Gluten content — Part 2: Determination of wet gluten and gluten index by mechanical means
• Effective Date: 12-Feb-2026

Overview

EN ISO 21415-2:2026 – Wheat and Wheat Flour: Gluten Content – Part 2: Determination of Wet Gluten and Gluten Index by Mechanical Means is a key international standard developed by CEN, based on ISO 21415-2:2026. This standard establishes a precise method for determining the wet gluten content and the gluten index in wheat flours-Triticum aestivum L. (common wheat) and Triticum durum Desf. (durum wheat)-using mechanical analysis.

The methodology defined in EN ISO 21415-2:2026 is applicable directly to wheat flours, and also to wheat grain samples after grinding, provided their particle size distribution complies with specific requirements. Determination of wet gluten and gluten index is an essential quality assessment in the grain, flour, and food production industries, supporting product standardization, contract compliance, and food safety regulations.

Key Topics

• Wet Gluten Content: The measurement of the viscoelastic protein complex comprising gliadin and glutenin, which determines the baking and processing quality of flour.
• Gluten Index: An indicator of gluten strength, calculated as the percentage of wet gluten that remains on a sieve after standardized centrifugation, reflecting protein quality and flour performance.
• Mechanical Method: Utilizes specialized automatic equipment (such as the Glutomatic unit) for consistent, reproducible results, minimizing manual variability.
• Applicability: Method applies to both flour and ground wheat samples, provided the granulometry meets set criteria, facilitating comprehensive quality testing across wheat products.
• Testing Procedure: Includes sample preparation, controlled mixing and washing, centrifuge-based separation, and accurate weighing and calculation steps.
• Performance Parameters: The standard details repeatability, reproducibility, and precision from interlaboratory studies, ensuring reliability for industrial and regulatory use.
• Reporting Requirements: Specifies mandatory documentation of sample details, method variations, and test outcomes for traceability and regulatory compliance.

Applications

EN ISO 21415-2:2026 has significant practical value for:

• Flour Mills and Producers: Enables standardized testing of gluten content and quality, supporting process optimization and consistent product quality.
• Bakeries and Food Manufacturers: Assures flour performance characteristics, directly impacting dough properties, bread volume, and texture.
• Quality Control Laboratories: Provides a harmonized, mechanical approach suitable for high-throughput environments, facilitating interlaboratory data comparability.
• Wheat Breeding and Research: Supports the characterization of wheat varieties for gluten quality, crucial for breeding programs and scientific studies.
• Regulatory Compliance: Serves as a recognized method in food law and trade, referenced in national and international standards and contracts.

Compliance with this standard helps stakeholders ensure that wheat and wheat flour meet stringent quality and safety benchmarks required by food legislation and commercial supply chains.

Related Standards

For comprehensive gluten analysis and harmonization with global practices, refer also to:

• EN ISO 21415-1: Wheat and wheat flour - Gluten content - Part 1: Determination of wet gluten by manual method
• EN ISO 21415-3 & 21415-4: Determination of dry gluten by oven-drying or rapid drying methods, respectively
• ICC 137/1: Official method for gluten index determination
• ICC 155: Wet gluten content determination guidance
• AACC Method 38-12.02: Standardized procedure for gluten index
• ISO 24333: Sampling protocols for cereals and milled products

Using EN ISO 21415-2:2026 alongside these related documents ensures thorough, harmonized gluten analytics across the wheat and flour supply chain.

Keywords: EN ISO 21415-2:2026, gluten content, gluten index, wheat flour, wet gluten determination, mechanical method, flour quality, bakery testing, food safety, cereal standards, CEN, ISO.

SLOVENSKI STANDARD
01-september-2026
Nadomešča:
SIST EN ISO 21415-2:2016
Pšenica in pšenična moka - Vsebnost glutena - 2. del: Določanje mokrega glutena
in indeksa glutena na mehanski način (ISO 21415-2:2026)
Wheat and wheat flour - Gluten content - Part 2: Determination of wet gluten and gluten
index by mechanical means (ISO 21415-2:2026)
Weizen und Weizenmehl - Glutengehalt - Teil 2: Bestimmung von Feuchtgluten und
Glutenindex durch mechanische Verfahren (ISO 21415-2:2026)
Blé et farines de blé - Teneur en gluten - Partie 2: Détermination du gluten humide et du
gluten index par des moyens mécaniques (ISO 21415-2:2026)
Ta slovenski standard je istoveten z: EN ISO 21415-2:2026
ICS:
67.060 Žita, stročnice in proizvodi iz Cereals, pulses and derived
njih products
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 21415-2
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2026
EUROPÄISCHE NORM
ICS 67.060 Supersedes EN ISO 21415-2:2015
English Version
Wheat and wheat flour - Gluten content - Part 2:
Determination of wet gluten and gluten index by
mechanical means (ISO 21415-2:2026)
Blé et farines de blé - Teneur en gluten - Partie 2: Weizen und Weizenmehl - Glutengehalt - Teil 2:
Détermination du gluten humide et du gluten index par Bestimmung von Feuchtgluten und Glutenindex durch
des moyens mécaniques (ISO 21415-2:2026) mechanische Verfahren (ISO 21415-2:2026)
This European Standard was approved by CEN on 29 May 2026.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 21415-2:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 21415-2:2026) has been prepared by Technical Committee ISO/TC 34 "Food
products" in collaboration with Technical Committee CEN/TC 338 “Cereal and cereal products” 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 December 2026, and conflicting national standards
shall be withdrawn at the latest by December 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 21415-2:2015.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 21415-2:2026 has been approved by CEN as EN ISO 21415-2:2026 without any
modification.
International
Standard
ISO 21415-2
Third edition
Wheat and wheat flour — Gluten
2026-05
content —
Part 2:
Determination of wet gluten and
gluten index by mechanical means
Blé et farines de blé — Teneur en gluten —
Partie 2: Détermination du gluten humide et du gluten index par
des moyens mécaniques
Reference number
ISO 21415-2:2026(en) © ISO 2026

ISO 21415-2:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 21415-2:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents . 2
6 Apparatus . 2
7 Sampling . 3
8 Preparation of test sample . 3
9 Procedure . 3
9.1 General .3
9.2 Testing .3
9.3 Paste preparation.3
9.4 Paste washing . .4
9.4.1 Washing time .4
9.4.2 Flour .4
9.4.3 Ground wheat .4
9.4.4 Special case .4
9.5 Spinning and weighing the wet gluten .4
9.6 Determining the gluten index .4
9.7 Number of measurements .5
10 Calculations and record of results . 5
11 Precision . 5
11.1 Interlaboratory test . .5
11.2 Repeatability .6
11.3 Reproducibility .6
11.4 Critical difference .7
11.4.1 Comparison of two sets of measurements in the same laboratory .7
11.4.2 Comparison of two sets of measurements in two laboratories .7
12 Test report . 8
Annex A (informative) Washing chamber and mill of the Glutomatic unit and centrifuge. 9
Annex B (normative) Preparation of ground wheat .12
Annex C (informative) Results of interlaboratory test .13
Annex D (informative) Proficiency tests data for commercial flours and wheats .20
Bibliography .29

iii
ISO 21415-2:2026(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 4, Cereals
and pulses, in collaboration with the European Committee for Standardization (CEN) Technical Committee
CEN/TC 338, Cereal and cereal products, in accordance with the Agreement on technical cooperation between
ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 21415-2:2015), which has been technically
revised.
The main changes are as follows:
— fidelity requirements (see Clause 10) have been changed in accordance with a new ring-test organized
by the Academy of National Food and Strategic Reserves Administration of China (see Annex C).
A list of all parts in the ISO 21415 series can be found on the ISO website.
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.

iv
ISO 21415-2:2026(en)
Introduction
[5]
The alternative techniques specified in this document and in ISO 21415-1 for isolation of wet gluten (i.e.
manual extraction and mechanical extraction) do not generally yield equivalent results. The reason for this
is that for full development of the gluten structure the dough needs to be allowed to rest. Hence, the result
obtained by manual extraction is usually greater than that obtained by mechanical extraction, especially
in the case of wheat with high gluten content. Therefore, the test report should always state the technique
used.
v
International Standard ISO 21415-2:2026(en)
Wheat and wheat flour — Gluten content —
Part 2:
Determination of wet gluten and gluten index by mechanical
means
1 Scope
This document specifies a method for determining the content of wet gluten and the gluten index for wheat
flours (Triticum aestivum L. and Triticum durum Desf.) by mechanical means.
This document is directly applicable to flours. It is also applicable to common and durum wheat after
grinding, if their particular size distribution meets the specification given in Table B.1.
[7] [8] [9]
NOTE This document is related to ICC 137/1 , ICC 155 and AACC Method 38-12.02 .
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
wet gluten
viscoelastic substance consisting mainly of two protein fractions (gliadin and glutenin) in hydrated form
[5]
Note 1 to entry: Wet gluten is obtained in the way indicated in this document or in ISO 21415-1 .
3.2
gluten index
mass of wet gluten (3.1) remaining on the sieve after centrifugation per 100 g of total wet gluten
Note 1 to entry: The higher the index, the stronger the gluten is.
3.3
ground wheat
result of experimental grinding of whole wheat
Note 1 to entry: The required granulometry is cited in Table B.1.
3.4
flour
finely milled wheat endosperm with a granulometry of less than 250 µm

ISO 21415-2:2026(en)
4 Principle
Preparation of a paste from a sample of flour or of ground wheat and a sodium chloride solution in the
equipment’s chamber. Separation of the wet gluten by washing this paste with a sodium chloride solution,
followed by removal of excess washing solution by centrifugation and weighing the residue. The gluten index
is obtained after centrifuging to force the wet gluten through a special sieve. The percentage of wet gluten
remaining on the sieve after centrifuging is defined as the gluten index.
5 Reagents
Use only reagents of recognized analytical grade, unless otherwise specified and distilled or demineralized
water, or water of equivalent purity.
5.1 Sodium chloride solution, 20 g/l.
Dissolve 200 g of sodium chloride (NaCl) in water, then dilute to 10 l. The temperature of the solution shall
be equilibrated to 22 °C ± 2 °C.
6 Apparatus
The usual laboratory apparatus and, in particular, the following items shall be used.
1)
6.1 Automatic gluten separation unit , (single or double) consisting of a washing/mixing chamber,
mill(s) (see Figures A.1 and A.2) and an electronically controlled distribution device for extracting the
gluten.
6.1.1 Mixing/washing chamber(s), fitted with replaceable chrome-plated sieve support(s) with polyester
sieves with an 88 µm mesh gap and polyamide sieves with an 840 µm mesh gap.
The distance between the mixing hook and the chrome-plated sieve support should be 0,7 mm ± 0,05 mm.
This value should be checked with the calibrated thickness shims supplied.
6.1.2 10 l plastic drum, to contain the sodium chloride solution (5.1) connected to the equipment by a
plastic tube.
6.1.3 Distribution system, consisting of a peristaltic pump allowing the sodium chloride solution (5.1)
used for washing the gluten to be delivered at a constant rate of between 50 ml/min and 56 ml/min.
For a detailed description of the unit and for detailed operating instructions, users of this document should
consult the leaflet of the maker of the equipment used.
6.2 Dispenser, for the sodium chloride solution, permitting delivery of 4,2 ml to 5,2 ml. The most used
volume is 4,8 ml and therefore the setting of the equipment shall be able to distribute this volume.
6.3 Centrifuge, capable of maintaining a rotational frequency of 6 000 ± 5 per minute and producing a
radial acceleration of 2 000g, fitted with two perforated plates with holes of diameter 600 µm or two sieve
cassettes with a 22 mm in diameter grid containing 600 µm holes, to determine the gluten index (see
Figures A.3 and A.4).
6.4 Balance, capable of weighing to the nearest 0,01 g.
6.5 Stainless steel spatula.
1) The Glutomatic System made by Perten Instruments AB (Sweden) is the mechanical device most widely used at
present for this purpose. This information is given for the convenience of users of this document and does not constitute
an endorsement by ISO of this product. Equivalent products may be used if they can be shown to lead to the same results.

ISO 21415-2:2026(en)
6.6 Beakers, with 500 ml capacity (to catch the rinsing water).
6.7 Stainless steel or plastic grippers.
6.8 Laboratory grinder, capable of producing a ground product with a granulometry meeting the
requirements of Table B.1.
7 Sampling
It is important for the laboratory to receive a truly representative sample which has not been damaged or
altered during transport or storage.
The method specified in this document does not cover sampling. A suitable sampling method is given in
[6] [4]
ISO 24333 or ISO 18390 .
8 Preparation of test sample
Homogenize the samples. Before measuring the gluten content, grind the wheat grains with a laboratory
grinder (6.8), as indicated in Annex B. Special precautions should be taken during grinding and storing to
prevent any alteration to the moisture content of samples.
9 Procedure
9.1 General
Automatic equipment (6.1) carries out the operations of preparation and washing of the dough continuously.
Follow the instructions supplied by the manufacturer of the equipment used.
Sample and sodium chloride solution shall be equilibrated at temperature of 22 °C ± 2 °C.
9.2 Testing
Weigh 10 g of the sample to within 0,01 g for testing and transfer to the unit’s washing/mixing chamber
(6.1.1). Ensure that the washing chamber is fitted with a suitable sieve, which has been previously cleaned
and moistened.
When testing flour samples, one or more fine polyester sieve(s) (88 µm aperture) is/are used. When testing
ground wheat, chrome-plated sieve supports fitted with a slotted ring are also required with polyamide
sieves with a mesh gap of 840 µm. In that case, the test starts with the fine sieve and in addition a coarse
sieve is used for the second step in the method.
The gluten index is generally measured using only 88 µm polyester sieves and 840 µm polyamide sieves for
the preparation of the wet gluten. If metal sieves are used, this shall be clearly noted in the test report.
9.3 Paste preparation
As a starting suggestion, add 4,8 ml of sodium chloride solution (5.1) to the test sample with the dispenser
(6.2). Aim the flow of saline solution at the chamber wall so that it does not go through the sieve. Gently
shake the washing chamber to ensure that the saline solution is uniformly distributed over the flour.
It can be necessary to adjust the amount of saline solution used for samples with very high or very low gluten
content. If forming a consistent paste turns out to be difficult (the chamber is flooded during washing), the
amount of saline solution added should be reduced (minimum of 4,2 ml). If very hard firm gluten forms
during mixing, the amount of solution should be increased to 5,2 ml.

ISO 21415-2:2026(en)
The mixing time is set by the manufacturer at 20 s, but this may be adjusted by the user, if necessary. If so,
the modified mixing time shall be reported when presenting the results in the test report (see Clause 12).
Contact the manufacturer to obtain information on adjusting the regulator.
9.4 Paste washing
9.4.1 Washing time
The washing time is set by the manufacturer to 5 min.
If the washing time is modified from the original 5 min, the modified washing time shall be reported when
presenting the results in the test report (see Clause 12).
9.4.2 Flour
A volume of 250 ml to 280 ml of sodium chloride solution is usually required for washing. The solution is
delivered automatically by the equipment at a constant pre-set rate of between 50 ml/min and 56 ml/min
(depending on the equipment).
9.4.3 Ground wheat
After 2 min of washing, stop the equipment, remove the washing chamber with the partially washed gluten
and transfer all the content, including bran particles, to another washing chamber containing a large-grade
sieve (840 µm). This can be done by placing the washing chamber beneath a gentle stream of cold water
(turning one sieve round to face the other and positioning the finer sieve on top).
Place the washing chamber with the coarser sieve containing the transferred lump of gluten in the working
position and continue washing until the washing sequence ends.
9.4.4 Special case
If the automatic washing process does not wash the paste sufficiently, and if the equipment allows it, preset
the dough washing time (9.3) at a higher value or adjust the distribution system flow rate (6.1.3).
9.5 Spinning and weighing the wet gluten
If the gluten index has to be determined, this operation is not needed, so go directly to 9.6.
When washing is complete, remove the wet gluten from the washing chamber using the grippers (6.7). Check
that no gluten remains inside the washing chamber.
Divide the gluten into two equal lumps and place them on the perforated plates of the centrifuge (6.3),
pressing down on them lightly.
Operate the centrifuge to remove the excess solution from the gluten (the pre-set time is 60 s). Remove the
gluten piece with the metal grippers (6.7) and weigh it all (m ) immediately to within 0,01 g (6.4).
There is no need to divide the gluten if a stabilizer is used inside the centrifuge.
If a double unit is used, two lumps of gluten will be pr
...