ISO INTERNATIONAL STANDARD 11289 First edition 1993-09-01 Heat-processed foods in hermetically sealed containers Determination of pH Produits alimentaires en conserves - Determination du pH ISO Referencenumber ISO 11289:1993(E) IS011289:1993(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)onall mattersof 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. ISO/TC Agricultural food products, Sub-Committee SC 9 Microbiology. ISO 1993 All rights reserved. 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 per- mission in writing from the publisher. International Organization for Standardization CasePostale56·CH-1211Geneve20·Switzerland Printed in Switzerland INTERNATIONAL STANDARD ISO11289:1993(E) Heat-processed foods in hermetically sealed containers Determination of pH 1 Scope Iso 3696:1987, Water for analytical laboratory use Specificationandtestmethods. This International Standard describes a potentiometric method for determining the pH of the aqueous phase 3 Definition of all types of food preserves. For the purposes of this International Standard, the It is particularly intended to be used to check the bio- following definition applies. logical stability of food preserves 3.1 pH of preserves: Potential difference at the This International Standard is applicable to thefollow ingfourclassesofproduct. measurementtemperaturebetweentwoelectrodes immersedintheagueousphaseofthepreservesor Class 1: homogeneous products with a liquid or thick inthesample(s)ofproduct(s)preparedinaccordance texture, or products exhibiting a large liquid or thick withtheproceduredescribedinthisInternational phase which imparts a presumed uniformity of pH to Standard. It is expressed in pH units, with an accuracy of 0,1 pH units. the product. Class 2: homogeneous pastes or heterogeneous 4. Principle products for which homogenization is necessary. Class 3: heterogeneous products with large solid Preparation of the test sample according to the class to which the product to be examined .belongs. components. Measurementofthepotentialdifferencebetweena Class 4: products whose liquid phase mainly consists glass electrode and a reference electrode immersed of oil or a water/oil emulsion. in the test sample. Measurements maybe made at 20 C or at 25C,the 5 Reagents temperature chosen being stated in the test report. Use only reagents of recognized analytical grade. 5.1 Water, complying with grade 1 of ISO 3696 distilled immediately before use so as to avoid the absorption of carbon dioxide. 2 Normative reference 5.2 Buffer solutions, for calibration of pH-meter. The following standard contains provisions which, through reference in this text, constitute provisions Use two standard buffer solutions,with pH values of this International Standard. At the time of publi- known to the second decimal at the measurement cation, the edition indicated was valid. All standards temperature, and encompassing the pH of the are subject to revision, and parties to agreements aqueous phase obtained from the test sample. basedonthisInternationalStandardareencouraged to investigate the possibility of applying the most re- NOTE1 As a general