5522 (ISO International Standard Fruits, vegetables and derived products -- Determination of total sulphur dioxide content Fruits, legumes et produits derivés -- Deétermination de la teneur en dioxyde de soufre total First edition -- 1981-09-01 UDC 634/635 : 543.845 Ref. No. ISO 5522-1981 (E) O 5522-1981 Descriptors : agricultural products, fruit and vegetable products, fruits, vegetables, chemical analysis, determination of content, sulphur dioxide. Price based on 7 pages ted without license from IHS NotforResale Foreword ISo (the International Organization for Standardization) is a worldwide federation of national standards institutes (lsO 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 5522 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. New Zealand Hungary Peru Austria Philippines Brazil India Bulgaria indonesia Poland Canada Israel Portugal Romania Chile Italy Kenya Cyprus South Africa, Rep. of Korea, Rep. of Czechoslovakia Spain Egypt, Arab Rep. of Libyan Arab Jamahiriya Thailand Ethiopia Malaysia Turkey France Netherlands Yugoslavia No member body expressed disapproval of the document. International Organization for Standardization, 1981 ? Printed in Switzerland Copyright International Organization for Standardization g permitted without license from IHS Not for Resale ISO 5522-1981 (E) INTERNATIONAL STANDARD Fruits, vegetables and derived products - Determination of total sulphur dioxide content 1 Scope and field of application 3.4 Indicator solution. This International Standard specifies a method for the deter- Dissolve 100 mg of bromophenol blue1) in 100 ml of mination of the total sulphur dioxide content of fruits, 20 % (V/ V) ethanol. vegetables and derived products, whatever the sulphur dioxide content. 3.5 Sodium hydroxide, standard volumetric solution, c(NaOH) = 0,1 mol/2), free from sulphate ions; or Principle 2 Sodium hydroxide, standard volumetric solution, 3.6 c(NaOH) =- 0,01 mol/3), free from sulphate ions. Acidification and heating of a test portion, then entrainment, in a current of nitrogen, of the sulphur dioxide liberated. Absorp- tion and oxidation of the sulphur dioxide by bubbling it through 3.7 lodine,standard volumetric solution, a neutral, dilute hydrogen peroxide solution. Determination of c(1/2 12) = 0,02 mol/14). the sulphuric acid thus formed using standard volumetric sodium hydroxide solution. 3.8 Starch, 5 g/l solution containing 200 g of sodium chloride (as preservative) per litre. Verification of the determination by precipitation of barium sulphate from the resulting solution, and, according to the Maintain the solution at boiling point for 10 min during prepara- sulphur dioxide content : tion. weighing of the barium sulphate (annex A); or 3.9 Potassium metabisulphite/EDTA solution. nephelometric determination (annex B). Dissolve inalittlewater1,20g of potassium metabisulphite (K2S2Os) and 0,20 g of the disodium salt of ethylenedinitrilo- 3 Reagents tetraacetic acid5). Transfer the solution quantitatively to a 1 000.ml one-mark volumetric flask. Make up to the mark with Ail reagents shall be of recognized analytical quality.The water water and mix. used shall be distilled water or water of at least equivalent purity, recently boiled. 3.10 Sucrose, 100 g/l solution. 3.1 Nitrogen, oxygen fr