ISO INTERNATIONAL STANDARD 10520 First edition 1997-09-01 Native starch - Determination of starch content - Ewers polarimetric method Amidons et fécules natifs - Dosage de I'amidon - Methode polarimetrique de Ewers ISO Reference number ISO 10520:1997(E) tted without license from IHS Not for Resale ISO 10520:1997(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 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. 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 ISO 10520 was prepared by Technical Committee Annexes A and B of this International Standard are for information only. @ISO1997 All rights reserved. Unless otherwise specified, no part of this publication may be photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case postale 56 : CH-1211 Geneve 20 . Switzerland internet [email protected] X.400 C=ch;a=400net; p=iso; =isocs; S=central Printed in Switzeriand Not for Resale ISO 10520:1997(E) INTERNATIONAL STANDARD ISO 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. 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 iso maintain registers of currently valid International Standards. ISO 1666:1996, Starch -- Determination of moisture content - Oven-drying method ISO 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. 3.2A second portion of the sample is treated with 40 % (V/M) ethanol to extract soluble sugars and polysaccharides of lower molecular mass. The fitrate 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 which should be of a size appropriate to ensure rapid temperature rise and steady temperature conditions. Not for Resale