SIST EN ISO 10520:1999

SLOVENSKI STANDARD
SIST EN ISO 10520:1999
01-maj-1999
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Native starch - Determination of starch content - Ewers polarimetric method (ISO
10520:1997)
Native Stärke - Bestimmung des Stärkegehaltes - Polarimetrisches Verfahren nach
Ewers (ISO 10520:1997)
Amidons et fécules natifs - Dosage de l'amidon - Méthode polarimétrique de Ewers (ISO
10520:1997)
Ta slovenski standard je istoveten z: EN ISO 10520:1998
ICS:
67.180.20 Škrob in izdelki iz njega Starch and derived products
SIST EN ISO 10520:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 10520:1999

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SIST EN ISO 10520:1999

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SIST EN ISO 10520:1999

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SIST EN ISO 10520:1999

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SIST EN ISO 10520:1999

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SIST EN ISO 10520:1999
INTERNATIONAL IS0
STANDARD
10520
First edition
1997-09-01
Native starch - Determination of starch
content - Ewers polarimetric method
Amidons et f&u/es natifs - Dosage de l’amidon - Mkthode polarim&rique
de Ewers
Reference number
IS0 10520: 1997(E)

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SIST EN ISO 10520:1999
IS0 10520:1997(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
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. IS0
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 member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 10520 was prepared by Technical Committee
ISOflC 93, Starch (including derivatives and by-products).
Annexes A and B of this International Standard are for information only.
0 IS0 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, induding
photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 l CH-1211 Gen&ve 20 l Switzerland
Internet central @ iso.ch
x.400 c=ch; a=4OOnet; p=iso; o=isocs; s=central
Printed in Switzerland
ii

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SIST EN ISO 10520:1999
IS0 10520: 1997(E)
INTERNATIONAL STANDARD @ IS0
Native starch - Determination of starch content -
Ewers polarimetric method
1 Scope
This International Standard specifies a polarimetric method for the determination of the starch
content of native starch, with the exception of starch with high amylose content.
It is not applicable to modified or pregelatinized (water-soluble) starch.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute
provisions of this International Standard. At the time of publication, the editions indicated were
valid. All standards are subject to revision, and parties to agreements based on this International
Standard are encouraged to investigate the possibility of applying the most recent editions of the
standards indicated below. Members of IEC and IS0 maintain registers of currently valid
International Standards.
Starch - Determination of moisture content - Oven-drying method
IS0 1666: 1996,
IS0 3696: 1987, Water for analytical laboratory use - Specification and test methods
3 Principle
The method includes two intermediate determination steps.
3.1 A portion of the sample is hydrolysed with dilute hydrochloric acid and the optical rotation
measured polarimetrically after clarification and filtration.
3.2 A second portion of the sample is treated with 40 % (VN) ethanol to extract soluble sugars
and polysaccharides of lower molecular mass. The filtrate is then subjected to the procedure given
in 3.1.
The difference between the measurements 3.1 and 3.2, multiplied by a factor, gives the starch
content of the sample.
NOTE - Key parameters of the method are the time and temperature of the hydrolysis, and the correct use
and calibration of the polarimeter. Consequently, the method includes constant agitation in the water bath,
which should be of a size appropriate to ensure rapid temperature rise and steady temperature conditions.

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SIST EN ISO 10520:1999
@ IS0
IS0 10520:1997(E)
4 Reagents
Use only reagents of recognized analytical grade, unless otherwise specified, and water complying
with grade 2 in accordance with IS0 3696.
4.1 Dilute hydrochloric acid, c(HCI) = 7,7 mol/l
Dilute 63,7 ml of hydrochloric acid (~20 = 1,19 g/ml) with water up to 100 ml.
4.2 Dilute hydrochloric acid, c(HCI) = 0,309 mol/l
1,19 g/ml) with water up to 1 000 ml.
Dilute 25,6 ml of hydrochloric acid (pgO =
NOTE -The concentration should be verified using sodium hydroxide solution [c(NaOH) = 0,l mol/l] and
Methyl red as indicator: 10 ml HCI should consume 30,94 ml of 0,l mol/l NaOH.
4.3 Dilute ethanol, 40 % (V/v) (pzo = 0,948 g/ml)
4.4 Carrez solution I
Dissolve 10,6 g of potassium hexacyanoferrate(ll) trihydrate [K4[Fe(CN),].3H20] in water. Dilute to
100 ml with water.
4.5 Carrez solution II
Dissolve 21,9 g of zinc acetate dihydrate [Zn(CH,C00),.2H,O] and 3 g of glacial acetic acid in
water. Dilute to 100 ml with water.
5 Apparatus
Usual laboratory apparatus and, in particular, the following.
5.1 Volumetric flasks, of capacity 100 ml.
5.2 Shaking boiling water bath, or boiling water bath equipped with a magnetic stirrer.
5.3 Polarimeter, adjusted to a wavelength of 589,3 nm, with 200 mm tubes.
54 . Analytical balance, capable of weighing to the nearest 0,001 g.
6 Preparation of test sample
If the particle size of the laboratory sample exceeds 0,5 mm, grind the sample to pass a sieve with
0,5 mm apertures. Homogenize the sample thus prepared.
2

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SIST EN ISO 10520:1999
IS0 10520: 1997(E)
0 IS0
7
Procedure
Carry out weighings to the nearest 0,001 g (see 5.4).
7.1 Determination of optical rotation of a total portion
7.1.1 Weigh 2,5 g + 0,05 g (m,) of the test sample and transfer it to a volumetric flask (5.1). Add
25 ml of the dilutehydrochloric acid (4.2) and agitate to distribute the test sample evenly. Add a
further 25 ml of the dilute hydrochloric acid (4.2).
7.1.2 Immerse the flask in the boiling water bath (5.2) and shake continuously or immerse the
flask in the boiling water bath equipped with a magnetic stirrer and stir at minimum speed.
7.1.3 Leave the flask for 15 min of: 5 s in the boiling water bath and stop shaking or stirring shortly
before removing it. Immediately add 30 ml of cold water and cool rapidly under flowing water to
20 “C * 2 “C
7.1.4 Add 5 ml of the Carrez solution I (4.4) and shake for 1 m
...