(ISO International Standard 5523 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION MEAYHAPOAHAR OPrAHW3ALWA nO CTAHAAPTW3AWUORGANISATION INTERNATIONALE DE NORMALISATION Liquid fruit and vegetable products - Determination of sulphur dioxide content (Routine method) Produits liquides derives des fruits et légumes -- Détermination de la teneur en dioxyde de soufre (Methode pratique) First edition - 1981-08-01 UDC 634/635 : 543.845 Ref. No. 1SO 5523-1981 (E) ISO 5523-1981 Descriptors : fruit and vegetable products, beverages, chemical analysis, determination of content, sulphur dioxide. Price based on 3 pages Not for Resale Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards institutes (Iso member bodies). The work of developing Inter- national Standards is carried out through IsO technical committees. Every member body interested in a subject for which a technical committee has been set up 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. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the ISO Council. International Standard ISO 5523 was developed by Technical Committee ISO/TC 34, Agricultural food products, and was circulated to the member bodies in July 1979. It has been approved by the member bodies of the following countries : Australia Germany, F. R. Netherlands Austria Hungary Poland Brazil India Portugal Bulgaria Indonesia Romania South Africa, Rep. of Canada Israel Chile Italy Spain Cyprus Kenya Thailand Korea, Rep. of Turkey Czechoslovakia Egypt, Arab Rep. of Libyan Arab Jamahiriya Yugoslavia Ethiopia Malaysia Mexico France The member body of the following country expressed disapproval of the document on technical grounds : New Zealand International Organization for Standardization, 1981 ? Printed in Switzerland nited without license from IHS Not for Resale ISO 5523-1981 (E) INTERNATIONAL STANDARD Liquid fruit and vegetable products - Determination of sulphur dioxide content (Routine method) O Introduction 4 Principle This method, which was developed for the determination of the 4.1 Free sulphur dioxide sulphur dioxide content of wines, has been found to be suitable for liquid fruit and vegetable products, and can be used as a Direct iodometric titration of the product at a pH between 0,7 rapid method. and 1, followed by a blank titration of the same product, freed from sulphur dioxide by boiling under reflux or by binding its In the case of more precise analyses, or in cases of dispute, the free sulphur dioxide content with an excess of acetaldehyde method specified in ISO 5522 shall be used. (ethanal) or propionaldehyde (propanal). 4.2 Bound sulphur dioxide 1 Scope and field of application After titration of the free sulphur dioxide, rendering of the pro duct alkaline and titration of the sulphur dioxide liberated by this hydrolysis with iodine in an acid medium. determination of the sulphur dioxide content of liquid fruit and vegetable products. A second iodometric titration after a second alkali hydrolysis permits titration of the sulphur dioxide which may have recom- bined, after the first hydrolysis, with any acetaldehyde present in the product. 2 References ISO/R 385, Burettes. 5 Reagents Iso 648, Laboratory glassware -- One-mark pipettes. All reagents shall be of recognized analytical quality and in par. ticular shall not contain impurities which could be determined ISO 1773, Laboratory glassware - Boiling flasks (narrow- as sulphur dioxide. The water used shall be distilled water or necked). water of at least equivalent purity, recently boiled. ISo 5522, Fruits, vegetables and derived products - Deter- 5.1 Sodium hydroxide, approximately 4 mol/I solution.1) mination of total sulphur dioxide content. Dissolve 160 g of sodium