ISO INTERNATIONAL STANDARD 750 Second edition 1998-08-01 Fruit and vegetable products - Determination of titratable acidity Produits dérivés des fruits et légumes - Deétermination de I'acidité titrable ISO Reference number ISO750:1998(E) T by IHS under lic Not for Resale ISO 750:1998(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 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 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 750 was prepared by Technical Commitee ISO/TC 34, Agricultural food products, Subcommittee SC 3, Fruit and vegetable products. @ISO1998 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic InternationalOrganizationforStandardization Casepostale 56·CH-1211Geneve 20·Switzerland Internet [email protected] Printed in Switzerland Not for Resale INTERNATIONAL STANDARD@ISO ISO 750:1998(E) Fruit and vegetable products Determination of titratable acidity 1 Scope This International Standard specifies two methods for the determination of the titratable acidity of fruit and vegetable products: a potentiometric reference method; a routine method using a coloured indicator. By convention, the latter method does not apply to wines. In the case of some coloured products,it may be difficult to determine the endpoint of the titration in the latter method and the former method should preferably be used. NOTE - The determination of titratable acidity is of no value in the case of products to which sulfur dioxide has been added. 2 Principle 2.1 Potentiometric method Potentiometric titration with a standard volumetric solution of sodium hydroxide. 2.2 Routine method 3 Reagents Use only reagents of recognized analytical grade, and distilled or demineralized water or water of equivalent purity. 3.1 Sodium hydroxide, standard volumetric solution, c (NaOH) = 0,1 mol/l.1) 3.2 Buffer solutions, of known pH. 3.3 Phenolphthalein, 10 g/l solution in 95 % (V/V) ethanol. 4 Apparatus Usual laboratory apparatus and, in particular, the following. 4.1 Homogenizer or mortar and pestle. 4.2 Pipettes, to deliver 25 ml, 50 ml or 100 ml. 1) Previously expressed as "0,1 N standard volumetric solution." Copyright Interr onal Organization for Standardizatior Not for Resale