6638/2 nternational Standard (ISO Fruit and vegetable products - Determination of formic acid content - Part 2 : Titrimetric method Produits derives des fruits et legumes -- Determination de la teneur en acide formique -- Partie 2 : Methode titrimetrique First edition -- 1984-11-01 Corrected and reprinted -- 1985-11-01 ) 6638/2-1984 (E) UDC 634.1/635.6:543.8:547.291 Ref.No.ISO6638/2-1984(E) Descriptors : agricultural products, fruits, vegetables, fruit and vegetable products, chemicalanalysis,determinationofcontent,formicacid. Price based on 3 pages No reproduction or networking permited without license from IHS Not for Resale Foreword Iso (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, govern- mental 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. They are approved in accordance with ISO procedures requiring at least 75 % approval by the member bodies voting. International Standard ISO 6638/2 was prepared by Technical Committee ISO/TC 34, Agricultural food products. International Organization for Standardization, 1984 Printed in Switzerland No reproduction or networking permited withoutlicense from IHS led by IHS t Not for Resale INTERNATIONAL STANDARD ISO6638/2-1984(E) Fruit and vegetable products - Determination of formic acid content Part 2 : Titrimetric method Scope and field of application 4 Apparatus This part of ISO 6638 specifies a titrimetric method for the Usual laboratory equipment and in particular determination of the formic acid content of fruit and vegetable products. 4.1 Analytical balance. A gravimetric method is specified in ISO 6638/1. 4.2 Distillation apparatus as shown in the figure, or equivalent apparatus, comprising 2 Principle 4.2.1 Steam generator, made of metal or glass, of capacity Quantitative entrainment by steam of the formic acid present in 5 litres. a test portion. Determination of the amount of iodine equivalent to the amount of bromine consumed by the acid in 4.2.2 Condenser, of length 50 cm. the distllate, by titration with sodium thiosulfate standard volumetric solution. 4.2.3 Flask, of capacity 500 ml. 3 Reagents 4.2.4 Volumetric flask, of capacity 1 000 ml. All reagents shall be of recognized analytical grade, and in par- 4.3 Conical flask, of capacity 500 ml, with a ground glass ticular shall be free from lead. The water used shall be distilled stopper. water or water of at least equivalent purity. 4.4 Burette. 3.1 Tartaric acid, crystalline. 4.5 Mixer and/or mechanical grinder. 3.2 Sodium acetate, 10 % (m/m) solution. 3.3 Potassium iodide, 10 % (m/m) solution. 5 Procedure 3.4 Bromoacetic acid. 5.1 Preparation of the test sample Dilute 8 g of bromine with glacial acetic acid to the mark in a 1 000 ml one-mark volumetric flask. Thoroughly mix the laboratory sample. If necessary, first remove stones and hard seed-cavity walls and pass through a mechanical grinder. 3.5 Sodium thiosulfate, standard volumetric solution, c(Na2S203) = 0,1 mol/1.1) Allow frozen or deep-frozen products to thaw in a closed vessel and add the liquid formed during this process to the product 3.6 Starch indicator, 1 % (m/m) solution. before mixing. 1) Hitherto expressed as "0,1 M standard volumetric solution". Copyright International Organization for Standardization 1 No reproduction or networking permited without license from IHS Not for Resale