SIST EN ISO 27971:2023

SLOVENSKI STANDARD
01-september-2023
Nadomešča:
SIST EN ISO 27971:2015
Žito in proizvodi iz žita - Navadna pšenica (Triticum aestivum L.) - Določevanje
alveografskih lastnosti testa pri stalnem dodajanju vode iz običajnih komercialnih
ali preskusnih mok in preskus postopka mletja (ISO 27971:2023)
Cereals and cereal products - Common wheat (Triticum aestivum L.) - Determination of
alveograph properties of dough at constant hydration from commercial or test flours and
test milling methodology (ISO 27971:2023)
Getreide und Getreideerzeugnisse - Weichweizen (Triticum aestivum L.) - Bestimmung
der Eigenschaften von Teig bei konstanter Flüssigkeitszufuhr zu handelsüblichen
Mehlen oder Versuchsmehlen bei gleichen Versuchsmahlverfahren mittels Alveograph
(ISO 27971:2023)
Céréales et produits céréaliers - Blé tendre (Triticum aestivum L.) - Détermination des
propriétés alvéographiques d'une pâte à hydratation constante de farine industrielle ou
d'essai et méthodologie pour la mouture d'essai (ISO 27971:2023)
Ta slovenski standard je istoveten z: EN ISO 27971:2023
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 27971
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2023
EUROPÄISCHE NORM
ICS 67.060 Supersedes EN ISO 27971:2015
English Version
Cereals and cereal products - Common wheat (Triticum
aestivum L.) - Determination of alveograph properties of
dough at constant hydration from commercial or test
flours and test milling methodology (ISO 27971:2023)
Céréales et produits céréaliers - Blé tendre (Triticum Getreide und Getreideerzeugnisse - Weichweizen
aestivum L.) - Détermination des propriétés (Triticum aestivum L.) - Bestimmung der
alvéographiques d'une pâte à hydratation constante de Eigenschaften von Teig bei konstanter
farine industrielle ou d'essai et méthodologie pour la Flüssigkeitszufuhr zu handelsüblichen Mehlen oder
mouture d'essai (ISO 27971:2023) Versuchsmehlen bei gleichen Versuchsmahlverfahren
mittels Alveograph (ISO 27971:2023)
This European Standard was approved by CEN on 4 May 2023.

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
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 27971:2023 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 27971:2023) 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 2023, and conflicting national standards
shall be withdrawn at the latest by December 2023.
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 27971:2015.
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 27971:2023 has been approved by CEN as EN ISO 27971:2023 without any modification.

INTERNATIONAL ISO
STANDARD 27971
Third edition
2023-06
Cereals and cereal products —
Common wheat (Triticum aestivum
L.) — Determination of Alveograph
properties of dough at constant
hydration from commercial or test
flours and test milling methodology
Céréales et produits céréaliers — Blé tendre (Triticum aestivum
L.) — Détermination des propriétés alvéographiques d'une
pâte à hydratation constante de farine industrielle ou d'essai et
méthodologie pour la mouture d'essai
Reference number
ISO 27971:2023(E)
ISO 27971:2023(E)
© ISO 2023
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
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CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 27971:2023(E)
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus . 2
7 Sampling . 6
8 Preparation of the wheat for laboratory milling . 6
8.1 Cleaning the laboratory sample . 6
8.2 Test portion . 6
8.3 Wheat moisture content determination . 6
8.4 Wheat preparation . 6
8.4.1 General . 6
8.4.2 Wheat with initial moisture content between 13 % and 15 % (one-stage
moistening) . 7
8.4.3 Wheat with a moisture content less than 13 % (two-stage moistening) . 7
8.4.4 Wheat with a moisture content greater than 15 % (preliminary drying
followed by moistening, as described above) . 7
9 Laboratory milling .7
9.1 General . 7
9.2 Milling procedure . . 8
9.2.1 Breaking . 8
9.2.2 Reduction . 8
9.2.3 Flour homogenization . 8
9.2.4 Storage of the flour . 9
9.3 Expression of milling results . 9
10 Preparation and Alveograph test .9
10.1 Preliminary checks . 9
10.2 Preliminary operations . 10
10.3 Kneading . 12
10.4 Preparation of dough test pieces . 14
10.5 Alveograph test . 15
10.5.1 Initial preparation . .15
10.5.2 First operation: placing the patty on the lower plate .15
10.5.3 Second operation: biaxial extension . 17
10.6 Expression of Alveograph test results . 17
10.6.1 General . 17
10.6.2 Maximum pressure parameter, P . 18
10.6.3 Mean abscissa at rupture, L . 18
10.6.4 Swelling index, G . 18
10.6.5 Elasticity index, I . 19
e
10.6.6 Curve configuration ratio, P/L . 19
10.6.7 Deformation work, W . 19
11 Precision .19
11.1 Interlaboratory tests . 19
11.1.1 Commercial flour . 19
11.1.2 Flour obtained from laboratory milling . 19
11.2 Repeatability limits . 20
iii
ISO 27971:2023(E)
11.2.1 General .20
11.2.2 Commercial flour — Limits established by the interlaboratory test .20
11.2.3 Flour obtained from laboratory milling . 20
11.3 Reproducibility limits . 21
11.3.1 General . 21
11.3.2 Commercial flour — Limits established by the proficiency tests . 21
11.3.3 Flour obtained from laboratory milling . 22
11.4 Uncertainty . 22
12 Test report .22
Annex A (informative) Characteristics of the mill suitable for obtaining a laboratory milled
flour .23
Annex B (normative) Quantity of water to be added to wheat for conditioning.25
Annex C (informative) Sample milling sheet .26
Annex D (informative) Conversion table from L to G.28
Annex E (informative) Interlaboratory and proficiency test data for commercial flours .30
Annex F (informative) Interlaboratory data for laboratory milled flour .40
Annex G (informative) Routine maintenance instructions for the Alveograph .52
Annex H (informative) Assessment of proteolytic activity in wheat (T. aestivum L.) or flour .54
Bibliography .56
iv
ISO 27971:2023(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 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 27971:2015), which has been technically
revised.
The main changes are as follows:
— the oldest instruments (before AlveoNG) have been removed;
— the latest instruments (AlveoPC and Alveolab) have been added.
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.
v
ISO 27971:2023(E)
Introduction
The end-use value of wheat is determined by a number of properties that are useful in the manufacture
of baked products such as bread, rusks and biscuits.
Such properties include the important viscoelastic (rheological) properties of dough formed as a result
of flour hydration and kneading. An Alveograph is used to study the main parameters by subjecting
a dough test piece to biaxial extension (producing a dough bubble) by inflating it with air, which is
similar to the deformation to which it is subjected during bread dough fermentation.
Recording the pressure generated inside the bubble throughout the deformation of the dough test piece
until it ruptures provides information on the following:
a) The resistance of the dough to deformation, or its stiffness. It is expressed by the maximum
pressure parameter, P.
b) The extensibility or the possibility of inflating the dough to form a bubble. It is expressed by the
mean of the abscissa value at rupture, L, converted to the swelling index, G.
c) The elasticity of the dough during biaxial extension. It is expressed by the elasticity index, I .
e
d) The work required to deform the dough bubble until it ruptures, or its strength, which is
proportional to the area of the Alveogram (sum of the pressures throughout the deformation
process). It is expressed by the parameter, W.
The P/L ratio is a measurement of the balance between stiffness and extensibility.
Alveographs are commonly used throughout the wheat and flour industry, for the following purposes:
— selecting and assessing different varieties of wheat and marketing batches of wheat;
— blending different batches of wheat or flour to produce a batch with given values for the Alveographic
criteria (W, P, and L) complying with the proportional laws of blending;
— assessing the proteolytic activity in wheat or flour to detect possible contamination (see Annex H
for more details).
Alveographs are used both on the upstream side of the industry for marketing, selecting and
assessing the different wheat varieties and on the downstream side throughout the baking industries
(see References [9], [11], [12] and [13]).
vi
INTERNATIONAL STANDARD ISO 27971:2023(E)
Cereals and cereal products — Common wheat (Triticum
aestivum L.) — Determination of Alveograph properties of
dough at constant hydration from commercial or test flours
and test milling methodology
1 Scope
This document specifies a method of determining, using an Alveograph, the rheological properties
of different types of dough obtained from common wheat flour (Triticum aestivum L.) produced by
industrial milling or laboratory milling.
It describes the Alveograph test and how to use a laboratory mill to produce flour in two stages:
— stage 1: preparation of the wheat grain for milling to make it easier to separate the bran from the
endosperm;
— stage 2: the milling process, including breaking between three fluted rollers, reduction of particle
size between two smooth rollers and the use of a centrifugal sieving machine to grade the 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 835, Laboratory glassware — Graduated pipettes
ISO 712, Cereals and cereal products — Determination of moisture content — Reference method
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 12099, Animal feeding stuffs, cereals and milled cereal products — Guidelines for the application of
near infrared spectrometry
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Principle
The behaviour of dough obtained from a mixture of flour and salt water is evaluated during
deformation. A dough disk (patty) is subjected to a constant air flow. At first it withstands the pressure.
Subsequently, it inflates into a bubble, according to its extensibility, and ruptures. The change in the
dough is measured and recorded in the form of a curve called an “Alveogram”.
ISO 27971:2023(E)
5 Reagents
Unless otherwise specified, use only reagents of recognized analytical grade, and only distilled or
demineralized water or water of equivalent purity.
5.1 Sodium chloride solution, obtained by dissolving (25 ± 0,2) g of sodium chloride (NaCl) in water
and then making the volume up to 1 000 ml. This solution shall not be stored for more than 15 days and
its temperature shall be (20 ± 2) °C when used.
5.2 Refined vegetable oil, low in polyunsaturates, such as peanut oil. It is possible to use olive oil
[1]
if its acid value is less than 0,4 (determined in accordance with ISO 660 ). Store in a dark place in a
closed container and replace regularly (at least every three months).
Alternatively, liquid paraffin (also known as “soft petroleum paraffin”), with an acid value of less than
or equal to 0,05 and the lowest possible viscosity [maximum 60 mPa·s (60 cP) at 20 °C].
5.3 Cold degreasing agent, optimum safety.
6 Apparatus
The usual laboratory apparatus and, in particular, the following shall be used.
6.1 Mechanical cleaner, fitted with sieves for wheat cleaning, in accordance with the manufacturer’s
instructions.
6.2 Conical or riffle sample divider.
6.3 Analytical balance, accurate to 0,01 g.
6.4 Glass burette, of 50 ml in capacity, graduated in 1 ml divisions.
1)
6.5 Rotary blender , for grain conditioning and flour homogenization, including the following
components:
6.5.1 Constant speed stirrer.
6.5.2 Two worm screws integral with the flask, possibly via the stopper (one for wheat preparation,
the other for flour homogenization).
6.5.3 Several wide-necked plastic flasks, 2 l capacity.
2)
6.6 Test mill (laboratory mill) , manually or automatically operated (see Annex A).
1) The CHOPIN Technologies MR2L rotary blender is an example of a suitable product available commercially. This
information is given for the convenience of users of this document and does not constitute an endorsement by ISO
of this product.
2) The CHOPIN Technologies Chopin-Dubois CD1 test mill is an example of a suitable product available commercially.
This information is given for the convenience of users of this document and does not constitute an endorsement by
ISO of this product.
ISO 27971:2023(E)
6.7 Complete Alveograph system (see Table 1 for specifications and characteristics of the
accessories) including the devices given in 6.7.1 to 6.7.3.
6.7.1 Kneading machine (see Figure 1 for the AlveoNG and AlveoPC models, and Figure 2 for the
3)
Alveolab model ), with accurate temperature control, for dough sample preparation.
6.7.2 Dedicated software, to record the pressure curve as a function of time, perform the
calculations and store the tests or other registration systems such as the Alveolink.
NOTE For details concerning the use of the different registration systems, see the manufacturer’s
instructions.
3)
6.7.3 Alveograph , for measuring the biaxial deformation of the dough test pieces (see Figure 1 for
the AlveoNG and AlveoPC models, and Figure 2 for the Alveolab model), including accurate temperature
control and hygrometry control for the Alveolab model, and having two rest chambers (three for the
Alveolab), each containing five plates on which the dough test pieces can be arranged to rest prior to
deformation.
6.8 Burette with stopcock, supplied with the apparatus (only for the AlveoNG and AlveoPC models),
160 ml capacity, graduated in divisions of 0,1 % of moisture content.
[8]
NOTE Throughout this document, “content” is expressed as a “mass fraction” (see ISO 80000-9 ), i.e. the
ratio of the mass of substance in a mixture to the total mass of the mixture.
6.9 Thermohydrograph for recording the test environment conditions (temperature and relative
air humidity) as specified in 9.1 and 10.1. In the case of the Alveolab, the test conditions (temperature
and humidity) around the swelling bubble are automatically checked and controlled by the device.
6.10 Volumetric flask, 1 000 ml capacity, conforming to the requirements of ISO 1042, class A.
6.11 Pipette, 25 ml capacity, graduated in divisions of 0,1 ml, conforming to the requirements
of ISO 835, class A.
3) The methods specified in this document are based on the use of the AlveoNG, AlveoPC and Alveolab models
of the CHOPIN Technologies Alveograph, which are examples of suitable products available commercially. This
information is given for the convenience of users of this document and does not constitute an endorsement by ISO
of these products.
ISO 27971:2023(E)
Table 1 — Specifications and characteristics of the accessories required for the test
Quantity Value and tolerance
Rotational frequency of the kneading blade (60 ± 2) Hz
Height of sheeting guides (12,0 ± 0,1) mm
Large diameter of the sheeting roller (40,0 ± 0,1) mm
Small diameter of the sheeting roller (33,3 ± 0,1) mm
Inside diameter of the dough cutter (46,0 ± 0,5) mm
Diameter of the aperture created when the moving plate opens (which determines the
(55,0 ± 0,1) mm
effective diameter of the test piece)
Theoretical distance between the fixed and moving plates after clamping (equal to the
(2,67 ± 0,01) mm
thickness of the test piece before inflation)
Volume of air automatically injected to detach the test piece prior to inflating the
(18 ± 2) ml
bubble
a
Air flow ensuring inflation (96 ± 2) l/h
a
On the AlveoNG and AlveoPC models, to adjust the flow rate of the air generator used to inflate the bubble, fit the nozzle
(see Figure 3) to create a specified pressure drop (and obtain a pressure corresponding to a height of 92 mmH O (12,3 kPa)
on the manometer chart). The air flow rate is set with the standardized pressure drop to obtain a pressure corresponding
to a height of 60 mm H O (8,0 kPa) on the manometer chart, i.e. (96 ± 2) l/h (see Figure 4). For the Alveolab model, this
control is automatized, and no particular action is required.
Key
A mixer 4 mixer control panel
B Alveograph 5 Alveograph control panel
1 burette for adding water 6 test plate of the Alveograph unit
2 mixer screen 7 resting chamber
ISO 27971:2023(E)
3 mixing bowl
Figure 1 — Mixer and Alveograph part of the AlveoNG and AlveoPC models
Key
1 mixing bowl 5 storage compartment for accessories
2 water injection nozzle 6 dough collector and humidifier
3 Aveolab control panel 7 resting chamber
4 Alveograph test chamber 8 salt water tank
Figure 2 — Mixer and Alveograph part of the Alveolab model
ISO 27971:2023(E)
Key
1 knurled ring 3 nozzle holder
2 nozzle 4 top plate
Figure 3 — Flow control system for the AlveoNG or AlveoPC models
7 Sampling
A representative wheat or flour sample should be sent to the laboratory. It shall not be damaged or
changed during transport or storage.
Sampling is not part of the method specified in this document. Recommended sampling methods are
[7]
given in ISO 24333 .
8 Preparation of the wheat for laboratory milling
8.1 Cleaning the laboratory sample
If necessary, pass the laboratory sample through a mechanical cleaner (6.1) to ensure that all stones
and metal fragments are removed and to avoid damaging the rollers during milling. A magnetic device
may also be used to remove ferrous metal fragments.
8.2 Test portion
The test portion shall be representative of the initial wheat mass. Use the sample divider (6.2) to
homogenize and divide the laboratory sample until the mass required for laboratory milling plus
moisture content determination is obtained. The minimum wheat mass of the test portion for milling
shall be 800 g.
8.3 Wheat moisture content determination
Determine the moisture content of the test portion as specified in ISO 712, or using a rapid device
[6]
(see ISO 7700-1 or ISO 12099).
8.4 Wheat preparation
8.4.1 General
Preparing the wheat for milling makes it easier to separate the bran from the endosperm. The target
moisture content is (16,0 ± 0,5) %.
ISO 27971:2023(E)
8.4.2 Wheat with initial moisture content between 13 % and 15 % (one-stage moistening)
Using the balance (6.3), weigh a test portion (minimum 800 g) to the nearest 1 g of wheat and pour it
into the blender.
Add the required amount of water (see Table B.1) to the grain from the burette (6.4) directly, or after
weighing it to the nearest 0,5 g.
Immediately after adding the water, insert the stopper fitted with the worm screw provided for use
with wheat into the flask, shake vigorously for a few seconds and place on the rotary blender (6.5).
Run the rotary blender for (30 ± 5) min (the time required to distribute the water evenly across the
surface of the grains).
Allow it to rest for a period that brings the total time of the moistening, shaking and resting operations
to (24 ± 1) h.
8.4.3 Wheat with a moisture content less than 13 % (two-stage moistening)
Since a larger volume of water is required, divide it into two halves and add in two stages during the
preparation period.
Proceed as described in 8.4.2, using only half the total quantity of water required (see Table B.1).
Shake the flask as described in 8.4.2 and allow it to rest for at least 6 h.
Then add the second half of the total quantity of water between the sixth and seventh hour.
After adding the second half, shake the flask again for (30 ± 5) min, then allow it to rest for a period that
brings the total time of the moistening, shaking and resting operations to (24 ± 1) h.
8.4.4 Wheat with a moisture content greater than 15 % (preliminary drying followed by
moistening, as described above)
The wheat shall be dried to produce a moisture content lower than 15 %.
Spread the laboratory sample in a thin layer to optimize the exchange between the grain and the air.
Allow to dry in the open air in a dry place for at least 15 h.
Perform the moisture content determination process again (see 8.3).
Then prepare the wheat as specified in 8.4.2 or 8.4.3, depending on the new moisture content.
9 Laboratory milling
9.1 General
The test mill (6.6) shall be used with the manufacturer’s settings. Additional weights shall not be used
and the tension on the reduction side spring shall not be changed.
The quality of the milling process depends on several factors:
a) environmental conditions that allow the final moisture content of the flour to be between 15,0 %
and 15,8 % (wheat should be milled in an ambient temperature between 18 °C and 23 °C with a
relative air humidity between 50 % and 75 %);
b) condition of the sieves; the sieving area shall remain uniform – if a sieve is pierced, it shall be
replaced immediately;
c) beater condition and setting: worn blades reduce the extraction rate;
ISO 27971:2023(E)
d) compliance with flow rates: the efficiency of the roll and the efficiency of the sieving process are
strictly dependent on a regular feed rate.
NOTE The speed at which the products pass through the sieving drum can be set by adjusting the
position of the blades on the beaters, i.e. two adjustable blades in the middle and at the end of the beater on
the break side, and four blades at the end on the reduction side.
9.2 Milling procedure
9.2.1 Breaking
Switch on the device.
Set the feed rate to allow 800 g of conditioned wheat to pass through the mill in (5 ± 1) min.
Pour the conditioned wheat (8.4) into the mill feed hopper and, at the same time, start the timer to
check the milling time.
After the last grains of wheat have passed through, let the mill continue to operate for (180 ± 30) s to
completely clear out the sieve.
When the mill stops, weigh (6.3), separately, the bran, the semolina and the flour to the nearest 0,1 g.
Calculate the percentage of semolina obtained compared with the mass of wheat used, expressing the
result to one decimal place.
9.2.2 Reduction
Switch on the device.
Adjust the feed rate to allow the semolina produced in 9.2.1 to pass through the mill in (5 ± 1) min.
Pour the semolina into the feed hopper and, at the same time, start the timer to check the time.
After the last grains of semolina have passed through, let the mill continue to operate for (180 ± 30) s to
completely clear out the sieve.
Repeat the above reduction procedure if the mass of semolina obtained from the break system is
greater than or equal to 48 % of the mass of conditioned wheat. (Round up the values: 47,4 becomes 47
and 47,5 becomes 48.)
When the mill stops, weigh (6.3), separately, the middlings and the reduction flour to the nearest 0,1 g.
Ensure that the milling ratio (ratio of the sum of the masses of the milled products to the total
conditioned wheat mass) is equal to at least 98 %.
NOTE A milling ratio less than 98 % indicates excessively worn beaters or an obstruction in the sieves,
causing some of the product to remain inside the sieving drum.
9.2.3 Flour homogenization
Pour the break and reduction flour into the blender flask (6.5.3).
Insert the stopper fitted with the worm screw (6.5.2) provided for use with flour into the flask and
place the flask on the blender (6.5).
Mix for (20 ± 2) min.
Remove the worm screw (6.5.2) and replace it with the flask stopper. The flour is now ready for the
Alveograph test.
ISO 27971:2023(E)
9.2.4 Storage of the flour
The flask containing the flour shall be kept in the room where the Alveograph test is performed.
9.3 Expression of milling results
Calculate the extraction rate, ER, as a percentage of dry mass, of flour extracted from the cleaned wheat
using Formula (1):
()100−×HM
ff
ER= ×100 (1)
()100−×HM
bb
where
H is the moisture content, as a percentage, of the flour obtained (determined in accordance
f
with ISO 712 or ISO 12099);
H is the moisture content, as a percentage, of the wheat test portion for milling before
b
moistening (determined in accordance with ISO 712 or ISO 12099);
M is the mass, in grams, of the total flour obtained;
f
M is the wheat mass, in grams, of the test portion for milling before moistening.
b
Express the result to the nearest 0,1 % mass fraction.
Calculate the percentage of bran, S, using Formula (2):
S =+MM/ M ×100 (2)
[]()
sb e
Calculate the percentage of middlings, R, using Formula (3):
RM=+[]/()MM ×100 (3)
rb e
where
M is the mass, in grams, of bran;
s
M is the mass, in grams, of middlings;
r
M is the initial mass, in grams, of the wheat before conditioning;
b
M is the mass, in grams, of water added (numerically equal to the volume, V , in millilitres, of
e e
water added).
Express the results to the nearest integer.
NOTE Annex C provides an example of a milling sheet to follow all interesting results.
10 Preparation and Alveograph test
10.1 Preliminary checks
Ensure that the ambient temperature is between 18 °C and 22 °C with a relative humidity between 50 %
and 80 %.
Ensure that the various components of the apparatus (kneading machine, Alveograph, burette, tools,
etc.) are clean.
ISO 27971:2023(E)
Check that the F-register (see Figure 5) is in place in the extrusion aperture to prevent any loss of flour
or salt solution leakage.
Ensure that the temperature of the kneading machine (6.7.1) at the start of the test is (24,0 ± 0,5) °C.
The temperature of the Alveograph shall be continuously set to (25,0 ± 0,5) °C.
A rise in the kneading machine temperature during the kneading process is normal and characteristic
of flour under test. The continuous control feature provided on the AlveoNG model should not be used.
Regularly check that the pneumatic circuit on the apparatus is sealed (no air leakage) by following the
manufacturer’s recommended procedure.
Check that the Alveograph plate is horizontal.
For the AlveoNG and AlveoPC models:
a
— check the air flow settings using the nozzle (see Table 1, footnote ) are creating the specified loss of
pressure (see Figures 3 and 4 c)):
— the air generator to a pressure corresponding to 92 mmH O (12,3 kPa) on the recorder
screen (see Figure 4 a));
— the micrometer flow rate valve to a pressure corresponding to 60 mmH O (8,0 kPa) on the
recorder screen (see Figure 4 b)).
a) 92 adjustment b) 60 adjustment
c) Command panel
Figure 4 — Measurement pressure setting
10.2 Preliminary operations
At the beginning of the test, the temperature of the flour shall be the ambient temperature.
Determine the moisture content of the flour in accorda
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