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1、A Reference number ISO 5530-2:1997(E) INTERNATIONAL STANDARD ISO 5530-2 Second edition 1997-12-15 Wheat flour Physical characteristics of doughs Part 2: Determination of rheological properties using an extensograph Farines de bl tendre Caractristiques physiques des ptes Partie 2: Dtermination des ca
2、ractristiques rhologiques au moyen de lextensographe Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:46:31 MDTNo reproduction or networking permitted without license from IHS
3、-,-,- ISO 5530-2:1997(E) ISO 1997 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Or
4、ganization for Standardization Case postale 56 CH-1211 Genve 20 Switzerland Internetcentraliso.ch X.400c=ch; a=400net; p=iso; o=isocs; s=central Printed in Switzerland ii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO mem
5、ber 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, governmen
6、tal 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. Draft International Standards adopted by the technical committees are circulated to the me
7、mber bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 5530-2 was prepared by Technical Committee ISO/TC 34, Agricultural food products, Subcommittee SC 4, Cereals and pulses. This part of IS
8、O 5530 is based on Standard No. 114 of the International Association for Cereal Science and Technology (ICC). This second edition cancels and replaces the first edition (ISO 5530-2:1988), which has been technically revised. ISO 5530 consists of the following parts, under the general title Wheat flou
9、r Physical characteristics of doughs: Part 1: Determination of water absorption and rheological properties using a farinograph Part 2: Determination of rheological properties using an extensograph Part 3: Determination of water absorption and rheological properties using a valorigraph Part 4: Determ
10、ination of rheological properties using an alveograph Annexes A to C of this part of ISO 5530 are for information only. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:46:31 M
11、DTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD ISOISO 5530-2:1997(E) 1 Wheat flour Physical characteristics of doughs Part 2: Determination of rheological properties using an extensograph 1Scope This part of ISO 5530 specifies a method, using an exten
12、sograph, for the determination of the rheological properties of a wheat flour dough in an extension test. The recorded load-extension curve is used to assess general quality of flour and its response to improving agents. The method is applicable to flour from wheat (Triticum aestivum L.). 2Normative
13、 references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO 5530. At the time of the publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO
14、5530 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 712:1),Cereals and cereal products Determination of moisture content Routine reference m
15、ethod. ISO 5530-1:1997, Wheat flour Physical characteristics of doughs Part 1: Determination of water absorption and rheological properties using a farinograph. 3Definitions For the purposes of this part of ISO 5530, the following terms and definitions apply. 3.1extensograph water absorption Volume
16、of water required to produce a dough with a consistency of 500 farinograph units (FU) after 5 min mixing, under the operating conditions specified in this part of ISO 5530. NOTE It is expressed in millilitres per 100 g of flour at 14,0 % (m/m) moisture content. 3.2stretching characteristics (of doug
17、h) Resistance of dough to extension and the extent to which it can be stretched until breaking, under the operating conditions specified in this part of ISO 5530. 1) To be published. (Revision of ISO 712:1985) Copyright International Organization for Standardization Provided by IHS under license wit
18、h ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:46:31 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 5530-2:1997(E) ISO 2 NOTE 1 The resistance is expressed in arbitrary units (extensograph units, EU). NOTE 2 The extent of stretching
19、is also expressed in arbitrary units (millimetrestransposition of the band of paper in the recorder). 4Principle Preparation of a dough from flour, water and salt in a farinograph under specified conditions. Moulding of a test piece on the balling unit and moulder of the extensograph into a standard
20、 shape. After a fixed period of time, stretching the test piece and recording the force required. Immediately after the first stretching, two repetitions, one after the other, with the same test piece, of moulding, rest period and stretching. The size and shape of the curves obtained are a guide to
21、the physical properties of the dough influencing the baking characteristics of the flour. 5Reagents Use only reagents of recognized analytical grade, and distilled or demineralized water, or water of equivalent purity. 5.1Sodium chloride 6Apparatus Usual laboratory apparatus and, in particular, the
22、following. 6.1Extensograph2), with a thermostat consisting of a constant temperature water bath (see annex A), with the following operating characteristics: - rotational frequency of balling unit: (83 3) min21 (rev/min);. - rotational frequency of moulder: (15 1) min21 (rev/min); - hook speed: (1,45
23、 0,05) cm/s; - chart speed : (0,65 0,01) cm/s; - force exerted per extensograph unit: (12,3 0,3) mN/EU (1,25 0,03) gf/EU. NOTE Some instruments have a different calibration for force/unit deflection. The procedure described may be used with such instruments, but it is necessary for the different cal
24、ibration to be taken into account when comparing the results with instruments calibrated as above. 6.2Farinograph, connected to a similar thermostat as the extensograph, with the operating characteristics specified in ISO 5530-1, and a burette as specified in ISO 5530-1. 6.3Balance, capable of weigh
25、ing to the nearest 0,1 g. 2) This part of ISO 5530 has been drawn up on the basis of the Brabender Extensograph. This information is given for the convenience of users of this part of ISO 5530 and does not constitute an endorsement by ISO of this apparatus. Other equipment may be used if it can be s
26、hown to give comparable results. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:46:31 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO ISO 5530-2
27、:1997(E) 3 6.4Spatula, made of soft plastic. 6.5Conical flask, of 250 ml capacity. 7Sampling Sampling is not part of the method specified in this part of ISO 5530. A recommended sampling method is given in ISO 13690. It is important that the laboratory receive a sample which is truly representative
28、and has not been damaged or changed during transport and storage. 8Procedure 8.1Determination of the moisture content of the flour Determine the moisture content of the flour using the method specified in ISO 712. 8.2Preparation of apparatus 8.2.1Turn on the thermostat of the farinograph (6.2) and c
29、irculate the water until the required temperatures are reached, prior to using the instrument. Before and during use, check the temperatures of - the thermostats, - the mixing bowl of the farinograph, in the hole provided for this purpose, and of - the extensograph cabinet. All temperatures shall be
30、 (30 0,2) C. 8.2.2Adjust the arm of the pen of the extensograph so as to obtain zero reading when a cradle with both its clamps plus a 150 g weight is placed in position. 8.2.3Pour some water into the trough of each cradle support, and place the supports, cradles and clamps in the cabinet at least 1
31、5 min before use. 8.2.4Uncouple the mixer of the farinograph from the driving shaft and adjust the position of the counterweight(s) so as to obtain zero deflection of the pointer with the motor running at the specified rotational frequency (see ISO 5530-1:1997, 6.1). Switch off the motor and then co
32、uple the mixer. Lubricate the mixer with a drop of water between the back-plate and each of the blades. Check that the deflection of the pointer is within the range (0 5) FU with the mixing blades rotating at the specified rotational frequency in the empty, clean bowl. If the deflection exceeds 5 FU
33、, clean the mixer more thoroughly or eliminate other causes of friction. Adjust the arm of the pen so as to obtain identical readings from the pointer and the recording pen. Adjust the damper so that, with the motor running, the time required for the pointer to go from 1 000 FU to 100 FU is (1,0 0,2
34、) s. 8.2.5Fill the burette of the farinograph, including the tip, with water at a temperature of (30 0,5) C. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:46:31 MDTNo reprod
35、uction or networking permitted without license from IHS -,-,- ISO 5530-2:1997(E) ISO 4 8.3Test portion If necessary, bring the flour to a temperature of (25 5) C. Weigh, to the nearest 0,1 g, the equivalent of 300 g of flour having a moisture content of 14 % ()m m/. Let this mass, in grams, be m; se
36、e table 1 in ISO 5530-1:1997, for m as a function of moisture content. Place the flour into the farinograph mixer. Cover the mixer and keep it covered until the end of mixing (8.4.2), except for the shortest possible time when water has to be added and the dough scraped down (see ISO 5530-1:1997, A.
37、2.2). 8.4Preparation of the dough 8.4.1Place (6,0 0,1) g of the sodium chloride (5.1) in the conical flask (6.5). Run in approximately 135 ml of water from the burette and dissolve the salt. For flours having a low water absorption, use a smaller volume of water. 8.4.2Mix in the farinograph mixer at
38、 the specified rotational frequency (see ISO 5530-1:1997, 6.1) for 1 min or slightly longer. Pour the salt solution (8.4.1) through a funnel into the centre hole of the bottom part of the lid, when a whole-minute line on the recorder paper passes by the pen. In order to reduce the waiting time, the
39、recorder paper may be moved forward during mixing of the flour. Do not move it backwards. NOTE 1 With older farinographs, the bowl of which is covered by a single plate (see ISO 5530-1:1997, A.2.2), the salt solution is poured into the right-hand front corner of the bowl. Add from the burette, into
40、the right-hand front corner of the mixer, a volume of water approximately equal to that expected to obtain a consistency of 500 FU after mixing for 5 min. When the dough forms, scrape down the sides of the bowl with the spatula (6.4), adding any adhering particles to the dough without stopping the m
41、ixer. If the consistency is too high, add a little more water to obtain a consistency of 500 FU after mixing for 5 min. Stop mixing and clean the mixer. NOTE 2 If the first dough meets the requirements of 8.4.3, test pieces from it can be moulded (8.4.4) and stretched (8.5.1). 8.4.3Make further mixi
42、ngs as necessary, until a dough is obtained - to which the salt solution and water have been added within 25 s, - the consistency of which, measured at the centre of the curve after mixing for 5 min, is between 480 FU and 520 FU, and - the mixing time of which is (5 0,1) min. Stop mixing after this
43、time. 8.4.4Take a support with two cradles from the cabinet of the extensograph (6.1); remove their clamps. Remove the dough from the mixer. Weigh a (150 0,5) g test piece. Place it in the balling unit and perform 20 revolutions of the plate. Remove the dough from the balling unit and pass it once t
44、hrough the moulder, ensuring that the test piece enters the back centrally, base first. Roll the test piece off the moulder into the centre of a cradle, and clamp it. Set the timer for 45 min. Weigh a second test piece, and ball, mould and clamp it in the same way. Place the support with two cradles
45、 and test pieces into the cabinet. NOTE 1 Very sticky doughs may be dusted lightly with rice flour or starch before being put into the moulder. NOTE 2 In the case of doughs showing substantial elastic recovery, the clamps should be held down for a few seconds to ensure that they fix the dough proper
46、ly. Clean the farinograph mixer. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:46:31 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO ISO 5530-2
47、:1997(E) 5 8.5Determination 8.5.1Exactly 45 min after clamping the first test piece, place the first cradle in the balance arm of the extensograph (6.1); the bridge between the two halves of the cradle shall be on the left-hand side so as not to be touched by the stretching hook when travelling. Adj
48、ust the pen to zero force. Immediately start the stretching hook. Observe the test piece (see note in 9.3). After rupture of the piece, remove the cradle. NOTE In recent extensographs, the hook automatically returns to its upper position. With older models it is necessary, by means of a switch, to stop the hook after breaking of the test piece, and to start it returning to its upper position. 8.5.2Collect the dough from the cradle and the hook. Repeat the balling and moulding operations as described in 8.4.4 on this test piece. Reset