EN ISO 10520:1998

Native starch - Determination of starch content - Ewers polarimetric method (ISO 10520:1997)

Migrated from Progress Sheet (TC Comment) (2000-07-10): UAP to be launched on this WI as soon as ISO 10520 is published. ++ gdj/1996_05_14

Native Stärke - Bestimmung des Stärkegehaltes - Polarimetrisches Verfahren nach Ewers (ISO 10520:1997)

Diese Internationale Norm legt ein polarimetrisches Verfahren zur Bestimmung des Stärkegehaltes von nativer Stärke, ausgenommen Stärke mit hohem Amylosegehalt, fest. Es ist nicht bei modifizierter Stärke oder Quellstärke (wasserlöslich) anwendbar.

Amidons et fécules natifs - Dosage de l'amidon - Méthode polarimétrique de Ewers (ISO 10520:1997)

La présente Norme internationale prescrit une méthode polarimétrique pour le dosage de l'amidon dans les amidons et fécules natifs, à l'exception de l'amidon à haute teneur en amylose. Elle n'est pas applicable aux amidons modifiés ou prégélatinés (solubles dans l'eau).

Nativni škrob - Določevanje vsebnosti škroba - Polarimetrijska metoda po Ewersu (ISO 10520:1997)

General Information

• Status: Published
• Publication Date: 22-Sep-1998
• Withdrawal Date: 30-Mar-1999
• ICS: 67.180 - Sugar. Sugar products. Starch
• Technical Committee: CEN/SS C10 - Starch
• Drafting Committee: CEN/SS C10 - Starch
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 23-Sep-1998
• Completion Date: 23-Sep-1998
• Ref Project: SIST EN ISO 10520:1999 - Native starch - Determination of starch content - Ewers polarimetric method (ISO 10520:1997)

Overview

EN ISO 10520:1998 specifies the Ewers polarimetric method for determining the starch content of native starches. This internationally recognized standard, issued by CEN and adopted from ISO 10520:1997, focuses on the quantitative analysis of native starch excluding high-amylose starch, and is not applicable to modified or pregelatinized starches. The method applies polarimetric measurement of optical rotation after specific chemical treatments, offering precise, reproducible starch content results essential for quality control and research in food, biochemical, and industrial starch applications.

Key Topics

• Scope: Applies to native starch starches, excluding high amylose and modified forms.

• Method Principle:

  • Hydrolyzing a starch sample with dilute hydrochloric acid.
  • Measuring optical rotation polarimetrically after clarification.
  • Extracting ethanol-soluble substances separately and measuring their rotation.
  • Subtracting the ethanol-soluble component's optical rotation to obtain starch content.

• Reagents: Analytical-grade hydrochloric acid solutions, 40% ethanol, Carrez clarification solutions.

• Apparatus: Includes polarimeter calibrated at 589.3 nm wavelength, volumetric flasks, shaking or magnetic stirring boiling water bath, and precision analytical balance.

• Test Procedure:

  • Preparation by grinding and homogenizing the sample.
  • Hydrolysis and measurement of total optical rotation.
  • Ethanol extraction and measurement of soluble substances optical rotation.
  • Determination of moisture content for final dry matter starch content calculation.

• Calculation: Starch content derived from optical rotation values, factoring in sample masses and moisture content.

• Precision: Repeatability and reproducibility rigorously tested through interlaboratory studies, ensuring reliable results across multiple venues.

• Reporting: Test reports must detail methods, results, repeatability checks, and all relevant test conditions or deviations.

Applications

• Quality Control in Food Industry: Accurate starch content determination in cereals, tubers, and starch derivatives crucial for product consistency, labeling, and nutritional analysis.
• Industrial Uses: Assists starch producers and users in pharmaceutical, paper, textile, and biodegradable materials industries for process monitoring and specification compliance.
• Research and Development: Enables scientists to characterize starch purity and composition in breeding, genetic modification, and functional property studies.
• Regulatory Compliance: Supports adherence to food and material standards where starch content measurement is mandated.
• Laboratory Standardization: Provides a harmonized, validated methodology for laboratories worldwide conducting starch quantification.

Related Standards

• ISO 1666:1996 – Determination of moisture content in starch by oven-drying, essential for calculating dry matter in EN ISO 10520.
• ISO 3696:1987 – Water quality for analytical laboratory use, ensuring reagent and process purity.
• ISO 5725 Series – Standards for method precision, repeatability, and reproducibility that validate the procedure’s robustness.
• ISO/TC 93 – Technical committee responsible for starch and its derivatives standardization efforts, related to starch testing and characterization.

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Keywords: EN ISO 10520, native starch, starch content determination, Ewers polarimetric method, polarimetry, starch analysis, starch quality control, starch testing standard, starch precision method, starch moisture content, starch measurement, ISO starch standards.

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-1999
1DWLYQLãNURE'RORþHYDQMHYVHEQRVWLãNURED3RODULPHWULMVNDPHWRGDSR(ZHUVX
,62
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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL IS0
STANDARD
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)
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
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.

@ 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.
IS0 10520: 1997(E)
0 IS0
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
...