ISO/TC 34/SC 4

Date: 2025-05-29

ISO/DIS 21415-2:2025(en)

Secretariat: SAC

Wheat and wheat flour — Gluten 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 par des moyens mécaniques

© ISO 2025

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Contents Page

Foreword 4

Introduction 5

1 Scope 1

2 Terms and definitions 1

3 Principle 1

4 Reagents 1

5 Apparatus 2

6 Sampling 3

7 Preparation of test sample 3

8 Procedure 3

8.1 General 3

8.2 Testing 3

8.3 Paste preparation 3

8.4 Paste washing 3

8.5 Spinning and weighing the wet gluten 4

8.6 Determining the gluten index 4

8.7 Number of measurements 5

9 Calculations and record of results 5

10 Precision 5

10.1 Interlaboratory tests 5

10.2 Repeatability 6

10.3 Reproducibility 6

10.4 Critical difference 7

11 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 tests 13

Annex D (informative) Interlaboratory and proficiency test data for commercial flours and wheats 18

D.1— Observation for wet gluten content on flour 21

Bibliography 27

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 WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 34, Food products, Subcommittee SC 4, Cereals and pulses.

This third edition of ISO 21415‑2 cancels and replaces the second edition (ISO 21415‑2:2015). It has been technically revised by adding reproducibility requirements (see 10.3) in accordance with practical observations in proficiency tests (see Annex D).

ISO 21415 consists of the following parts, under the general title Wheat and wheat flour — Gluten content:

— Part 1: Determination of wet gluten by a manual method

— Part 2: Determination of wet gluten and gluten index by mechanical means

— Part 3: Determination of dry gluten from wet gluten by using an oven-drying method

— Part 4: Determination of dry gluten from wet gluten by a rapid drying method

Introduction

The alternative techniques specified in this part of ISO 21415 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.

Wheat and wheat flour — Gluten content — Part 2: Determination of wet gluten and gluten index by mechanical means

This part of ISO 21415 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 method is directly applicable to flours. It also applies to common and durum wheat after grinding, if their particular size distribution meets the specification given in Table B.1.

For the purposes of this document, the following terms and definitions apply.

2.1

wet gluten

viscoelastic substance consisting mainly of two protein fractions (gliadin and glutenin) in hydrated form, obtained in the way indicated in this part of ISO 21415 or in ISO 21415‑1

2.2

gluten index

mass proportion of wet gluten remaining on the sieve after centrifugation

Note 1 to entry: The higher the index, the stronger the gluten is.

2.3

ground wheat

result of experimental grinding of whole wheat with the granulometry cited in Table B.1

2.4

flour

finely ground wheat endosperm with a granulometry of less than 250 µm

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.

Use only reagents of recognized analytical grade, unless otherwise specified and distilled or demineralized water, or water of equivalent purity.

4.1 Sodium chloride solution, 20 g/l.

Dissolve 200 g of sodium chloride (NaCl) in water, then dilute to 10 l. When using this, it is recommended that the temperature of the solution be 22 °C ± 2 °C.

4.2 Solution of iodine/potassium iodide (Lugol’s solution).

Dissolve 2,54 g of potassium iodide (KI) in water. Add 1,27 g of iodine (I₂) to this solution and, when the reagents have completely dissolved, dilute to 100 ml with water.

Usual laboratory apparatus and, in particular, the following items.

5.1 Automatic gluten separation unit ^[1], (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.

5.1.1 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 shall be 0,7 mm ± 0,05 mm. This value should be checked with the calibrated thickness shims supplied.

5.1.2 10 l plastic drum, to contain the sodium chloride solution (4.1) connected to the equipment by a plastic tube.

5.1.3 Distribution system, consisting of a peristaltic pump allowing the sodium chloride solution (4.1) 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 part of ISO 21415 should consult the leaflet of the maker of the equipment used.

5.2 Dispenser, for the sodium chloride solution, permitting delivery of 3 ml to 10 ml with an accuracy of ±0,1 ml.

5.3 Centrifuge, capable of maintaining a rotational frequency of 6 000 ± 5 per minute and producing a radial acceleration of 2 000 g, fitted with 2 perforated plates with holes of diameter 600 µm or 2 sieve cassettes with a 22 mm in diameter grid containing 600 µm holes, to determine the gluten index (cf. Figures A.3 and A.4).

5.4 Balance, with a display precision of 0,001 g and capable of weighing to the nearest 0,01 g.

5.5 Stainless steel spatula.

5.6 Beakers with 500 ml capacity (to catch the rinsing water).

5.7 Stainless steel or plastic grippers.

5.8 Lab grinder , capable of producing a ground product with a granulometry meeting the requirements of Table B.1.

5.9 Watch glass.

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 part of ISO 21415 does not cover sampling. A recommended sampling method is given in ISO 24333.

Homogenize the samples. Before measuring the gluten content, grind the wheat grains with a lab grinder (5.8), as indicated in Annex B. Special precautions should be taken during grinding and storing to prevent any alteration to the moisture content of samples.

The operations of preparation and washing of the dough are carried out continuously with automatic equipment (5.1). 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

Weigh 10 g of the sample to within 0,01 g for testing and transfer to the unit’s washing/mixing chamber (5.1.1). 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.

As a starting suggestion, add 4,8 ml of sodium chloride solution (4.1) to the test sample with the dispenser (5.2). 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 may 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.

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 (11). Contact the manufacturer to obtain information on adjusting the regulator.

The washing time is set by the manufacturer to 5 minutes.

For the detection of starch, press out some drops of the washing solution from the gluten ball into a watch-glass (5.9) and add a few drops of a solution of iodine (4.2) to it. If the colour of the solution does not change, the washing out procedure is completed. If the colour of the solution turns into blue, it indicates that starch is still present and the washing out procedure should be continued until the starch cannot be detected.

If the washing time is modified from the original 5 minutes, the modified mixing time shall be reported when presenting the results in the test report (11).

The washing time is set by the manufacturer at 5 min. 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).

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.

If the automatic washing process does not wash the paste sufficiently, and if the equipment allows it, preset dough mixing time (8.3) at a higher value or adjust distribution system flow rate (5.1.3).

If the gluten index has to be determined, this operation is not needed, so go directly to 8.6.

When washing is complete, remove the wet gluten from the washing chamber using the grippers (5.7). 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 (5.3), 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 (5.7) and weigh it all (m₁) immediately to within 0,01 g (5.4).

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 produced. These should be treated separately placed on one of the perforated plates respectively.

If excess moisture is always present, remove the wet gluten after centrifugation, gently rub the gluten ball in the palm until it slightly stick to the hand, and then weigh.

The extracted lump of gluten shall be centrifuged, without dividing it. Hence, two gluten measurements should be taken at the same time. This operation is possible with a double-facility unit. In case of a single-facility unit, a counterweight should be used during centrifuging.

After washing (8.4) and omitting the spin (8.5), use the grippers (5.7) to place the lump of gluten in the sieve cassette (5.3) provided. This is a tricky operation and shall not stretch or compress the gluten. The interval between the end of the washing cycle and the start of centrifuging should be between 20 s and 30 s. Centrifuging is programmed for 60 s.

After centrifuging, remove the sieve cassette and check that no gluten remains inside the centrifuge. Using the spatula (5.5), carefully scrape up all the gluten which has passed through the sieve. Weigh this (m₂) to within 0,01 g (5.4). Leave this quantity on the balance and add the gluten remaining on the sieve (inside the sieve cassette) to estimate the total mass (m₁) of wet gluten.

Only the sieve cassette (5.3) should be used for the gluten index determination.

Take two measurements from the same sample. If the difference between the two measurements exceeds the repeatability limit, perform two new measurements.

9.1 The wet gluten content ( G_w), expressed as a percentage by mass, is calculated with the Formula (1):

G_w = m₁ × 10 (1)

where m₁ is the mass of wet gluten (see 8.5), in grams.

The result will be the arithmetical average of two readings if the repeatability conditions (see 10.2) are observed. Express the result to within one decimal place.

9.2 The gluten index (G_i) is calculated with Formula (2):

(2)

where

m₁ is the total mass of wet gluten, in grams;

m₂ is the mass of gluten, in grams, that has passed through the sieve.

The result will be the arithmetical average of two readings if the repeatability conditions (see 10.2) are observed. Express the result to within one unit.

Details of the interlaboratory tests in terms of the method’s precision are summarized in Annexes C and D. The values obtained from these tests may not apply to concentration ranges and matrices other than those stated in the field of application.

The range of values studied in the ring test are in the following table 1.

Table 1 — Ranges of values in the interlaboratory test

The range of values observed in proficiency tests are in the following table 2.

Table 2 — Ranges of values in the proficiency tests

The repeatability of this document was determined through calculations based on multiple laboratory validation results, as shown in Annex C. The standard deviation of repeatability (S_r) and the repeatability limit (r) are shown in Table 3.

The absolute difference between two independent test results obtained by the same method, on an identical material tested in the same laboratory by the same operator using the same equipment within a short period of time, will in not more than 5 % of cases be greater than the values given below.

Table 3 — Repeatability limit

The reproducibility of this document was determined through calculations based on multiple laboratory validation results, as shown in Appendix C. The standard deviation of reproducibility (S_R) and the reproducibility limit (R) are shown in Table 4.

The absolute difference between two individual test results, obtained by the same method on an identical material tested in different laboratories by different operators using different equipment, will in not more than 5 % of cases be greater than the values given.

Table 4 — Reproducibility limit from the ring-test results (Annex C)

Other reproducibility limits, R, are obtained by the equations below calculated from the proficiency testing data given in Annex D.

Table 5 — Reproducibility limit from the proficiency tests (Annex D)

The critical difference, D_r, is the deviation between two averaged values obtained from two test results in conditions of repeatability.

D_r = 2,8S_r = 2,8S_r = 1,98S_r

where

S_r is the standard deviation of repeatability;

n₁ and n₂ are the number of test results corresponding to each of the averaged values.

Table 6 — Critical difference of repeatability from the ring-test results (Annex C)

The critical difference, D_R, is the deviation between two average values obtained from two test results in conditions of reproducibility.

D_R = 2,8 = 2,8

where

S_R is the standard deviation of reproducibility;

S_r is the standard deviation of repeatability;

n₁ and n₂ are the number of test results corresponding to each of the averaged values.

The critical differences D_R in the following table 7 are obtained by the equations above.

Table 7 — Critical difference of reproducibility from the ring-test results (Annex C)

The test report shall contain at least the following information:

a) all information needed for complete identification of the sample;

b) the method used and the reference to this part of ISO 21415 (ISO 21415‑2);

c) all operational details not stipulated in this part of ISO 21415 or considered as optional, and the details of any incidents likely to have had repercussions for the test result(s);

d) if the tests were carried out in conditions of repeatability, the final result obtained.

1. 
   (informative)
   
   Washing chamber and mill of the Glutomatic unit and centrifuge

The apparatus shown in Figures A.1 and A.2 is that given in Reference [6].

Dimensions in millimetres

Key

1 mixing/washing chamber

2 kneader

Figure A.1 — Equipment for separating the gluten

Dimensions in millimetres

Figure A.2—Kneader

Figure A.3—Centrifuge

Figure A.4—Centrifuge cassette for the gluten index

1. 
   (normative)
   
   Preparation of ground wheat

As stated in the field of application, this method also applies to wheat after grinding in a lab grinder (5.8).

Gluten formation and washing are influenced by the granulometry of grinded samples. The grinder used shall be capable of producing a grinded product meeting the specifications in Table B.1.

Table B.1 — Sieve mesh gap and granulometry required for samples

It should be emphasized that Table B.1 is used for on-going adjustment of the grinder. All the grounds (grinded product) are subjected to measurement. Granulometry should be checked regularly by using a completely homogenized sample and a suitable laboratory sifter.

The grinding method used to prepare the grinded wheat sample influences the results of gluten content measurement. Different grinders will produce a different distribution of granulometric fractions, and this will introduce variations into formation of the paste and the washed gluten. To obtain comparable results, the same sample preparation method should be used.

Grind a representative sample of wheat so that it meets the granulometry specifications appearing in Table B.1. The grinder should be carefully supplied with wheat to avoid overheating and overloading. Grinding should continue for 30 s to 40 s after all the sample has entered the grinder. To complete grinding, the wheat should be withdrawn in small quantities (up to 1 %).

It is important not to discard any part of the grinded wheat as, for example bran fractions, because that can introduce a bias in the gluten content and the gluten index.

1. 
   (informative)
   
   Results of interlaboratory tests

The repeatability and reproducibility limits for common wheat and wheat flour in this method are derived by calculating the results of an interlaboratory tests that were organised by the Academy of National Food and Strategic Reserves Administration of China.

The results obtained were subjected to statistical analysis in accordance with ISO 5725‑1, ISO 5725‑2 and ISO 5725‑6 to obtain the reliable data appearing in Tables C.1 and C.2 and Figures C.1 and C.2.

The results were obtained from 14 laboratories by measuring 11 samples of wheat and 11 samples of wheat flour. The measurements were performed in duplicate.

Table C.1 — Test results of wet gluten content on wheat

Table C.2 — Test results of wet gluten content on flour

Figure C.1 — Fitting curve of wet gluten content and standard deviation in wheat samples

Figure C.2 — Fitting curve of wet gluten content and standard deviation in flour samples

The ratio indicated in figures C.1 and C.2 suggest that the standard deviations of repeatability and reproducibility are constant whatever the wet gluten level.

Table C.3 — Test results of gluten index on wheat

Table C.4 — Test results of gluten index on flour

Figure C.3 —Fitting curve of gluten index and standard deviation in wheat samples

Figure C.4 — Fitting curve of gluten index and standard deviation in flour samples

The ratio indicated in figures C.3 and C.4 suggest that the standard deviations of repeatability and reproducibility are constant whatever the gluten index level.

1. 
   (informative)
   
   Interlaboratory and proficiency test data for commercial flours and wheats

The repeatability and reproducibility limits of the method used for commercial flour and milled wheat were initially established within the context of an interlaboratory test in which 14 laboratories participated. The test was performed on 3 samples of common wheat, 3 samples of durum wheat and 2 samples of flour. Measurements were performed in duplicate.

In order to extend the concentration range of wet gluten content and gluten index and to have more realistic reproducibility limits, the results obtained from the proficiency tests organized by the BIPEA (France) were studied.

During 30 consecutive months, more than 100 laboratories on flour, 60 to 80 laboratories on common wheat and 10 to 19 laboratories on durum wheat participated in the tests between 2018 and 2021. Out of these laboratories, 70 % of total population for flour, 90 % of total population for common wheat and 100 % of total population for durum wheat were used in the data set used when the new reproducibility limits were obtained from 30 values of interlaboratory standard deviation. Repeatability limits cannot be extracted from proficiency tests because participants are asked to deliver only one value (generally an average of 2 determinations).

It shall be clear when comparing the results of the interlaboratory test and the proficiency program, that in an interlaboratory test for a standard method, the performance of the laboratory and the instruments used are monitored and reviewed before the tests are performed and the results are collected. In the proficiency program, no control of the participating labs or instruments are made by the organizer. As a result of this, there may be an increased variation seen in the proficiency test results based on instrument deficiencies or operator mistakes rather than from the method itself. Hence, for a laboratory seeking guidance on performance, the results in the proficiency test reproducibility data give a good indication of what to expect from the method when comparing results between laboratories in daily operation, while the interlaboratory test reproducibility is a target to try to reach through careful care of the instruments and the execution of the analysis in the laboratory.

• 1. Observation for wet gluten content on flour

Figure D.1 — Relationship between wet gluten content and interlaboratories standard deviations for flour (data from the proficiency tests)

X : assign value of wet gluten content (%) on industrial flour

Y : interlaboratories standard deviation observed

Average value of standard deviation = 1,1

R² = 0,014 6

The ratio indicated above suggests that the standard deviations of reproducibility is constant whatever the wet gluten level.

• 1. Observation for wet gluten content on common wheat

Figure D.2 — Relationship between wet gluten content and interlaboratories standard deviations for common wheat (data from the proficiency tests)

X : assign value of wet gluten content (%) on common wheat

Y : interlaboratories standard deviation observed

Average value of standard deviation = 1,3

R² = 0,231 1

The ratio indicated above suggests that the standard deviations of reproducibility is constant whatever the wet gluten level.

• 1. Observation for wet gluten content on durum wheat

Figure D.3 — Relationship between wet gluten content and interlaboratories standard deviations for durum wheat (data from the proficiency tests)

X : assign value of wet gluten (%) content on common wheat

Y : interlaboratories standard deviation observed

Average value of standard deviation = 1,5

R² = 0,211 6

The ratio indicated above suggests that the standard deviations of reproducibility is constant whatever the wet gluten level.

• 1. Observation for gluten index on flour

Figure D.4 — Relationship between gluten index and interlaboratories standard deviations for flour (data from the proficiency tests)

X : assign value of gluten index (%) of flour

Y : interlaboratories standard deviation observed

Y = - 0,599 4 X + 60,184

R² = 0,963 9

Figure D.4 shows that the standard deviations of reproducibility are dependent on the mean values of gluten index of flour.

• 1. Observation for gluten index on common wheat

Figure D.5 — Relationship between gluten index and interlaboratories standard deviations for common wheat (data from the proficiency tests)

X : assign value of gluten index (%) of flour

Y : interlaboratories standard deviation observed

Y = - 0,518 7 X + 52,553

R² = 0,965 9

Figure D.5 shows that the standard deviations of reproducibility are dependent on the mean values of gluten index of common wheat.

• 1. Observation for gluten index on durum wheat

Figure D.6 — Relationship between gluten index and interlaboratories standard deviations for durum wheat (data from the proficiency tests)

X : assign value of gluten index (%) of flour

Y : interlaboratories standard deviation observed

Average value of standard deviation = 12,2

R² = 0,042 7

The ratio indicated above suggests that the standard deviation of reproducibility is constant whatever the gluten index.

Bibliography

[1] ISO 5725‑1, Accuracy (trueness and precision) of measurement methods and results — Part 1: General principles and definitions

[2] ISO 5725‑2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method

[3] ISO 5725‑6, Accuracy (trueness and precision) of measurement methods and results — Part 6: Use in practice of accuracy values

[4] ISO 21415‑1, Wheat and wheat flour — Gluten content — Part 1: Determination of wet gluten by a manual method

[5] ISO 21415‑3, Wheat and wheat flour — Gluten content — Part 3: Determination of dry gluten from wet gluten by an oven drying method

[6] ISO 21415‑4, Wheat and wheat flour — Gluten content — Part 4: Determination of dry gluten from wet gluten by a rapid drying method

[7] ISO 24333, Cereals and cereal products — Sampling

[8] ICC Standard No. 137/1, Mechanical Determination of the Wet Gluten Content of Wheat Flour (Glutomatic)

[9] ICC Standard No. 155, Determination of Wet Gluten Quantity and Quality (Gluten Index ac. to Perten) of Whole Wheat Meal and Wheat Flour (Triticum aestivum)

[10] Cereals and Grains Association official method N° 38-10.01 Gluten – Hand Washing Method

[11] Cereals and Grains Association official method N° 38-12.02 Wet Gluten, Dry Gluten, Water-Binding Capacity and Gluten Index

1. The Glutomatic unit (types 2100 and 2200) made by Perten Instruments AB (Sweden) is the mechanical device most widely used at present for this purpose. This information is given for the benefit of users of this part of ISO 21415 and in no way implies that ISO approves or recommends exclusive use of this device. Other equipment may also be used if it yields similar results to those of the Glutomatic unit or those of the method described in ISO 21415-1. ↑