RESOLUTION OENO 13/2008

CHARACTERISTICS OF THE METHOD FOR DETERMINING THE SULPHUR DIOXIDE CONTENT OF WINE VINEGAR – AMENDMENTS TO THE METHOD

THE GENERAL ASSEMBLY

IN VIEW of Article 2 paragraph 2 iv of the Agreement establishing the International Organisation of Vine and Wine

HAVING STUDIED the research by the Methods of Analysis Sub-commission, with particular regard to the characteristics of the two methods for determining the concentration of in wine vinegar

CONSIDERING resolution OENO 60/2000 on the method for determining the sulphur dioxide content in wine vinegars

DECIDES upon the proposal of Commission II "Oenology", to amend resolution OENO 60/2000 and particularly to replace points 8 and 9 of the resolution with the following points:

8 – Characteristics of the method

8.1 Repeatability of the iodometry method for determining in vinegar

Seven red wine vinegars and five white wine vinegars were analysed in duplicate in order to determine the repeatability parameters (table 1).

Table 1 Total content in different vinegars in mg/l

Mean = 75.54 mg/l

Repeatability: standard deviation=4.4; r limit= 12.38 mg/l

Relative repeatability r = 15%

8.2 Recovery rate of added concentrations

Quantities of were added to different vinegars in order to calculate the recovery rate of the iodometry determination method (table 2).

Table 2 Study of recovery rate of known concentrations added to different vinegars

The recovery rate varies from 44% to 100%: occasionally it is too low, but is nonetheless more acceptable than the rate noted for the method of drying under a nitrogen stream, which sometimes produces excessive values.

9 – Important remark

After studying the application of the reference method for the determination of sulphur dioxide described in the Compendium of International Methods of Analysis of Wine and Must to vinegars, the results produced are unsatisfactory in terms of the recuperation rate of added concentrations, which appears to be due to the very high concentration of acetic acid.

10 - Bibliography

1. Curvelo-Garcia A.S. and Godinho M.C., 1986. Determinação analítica do dióxido de enxofre em vinagres. Optimização das condições operatórias, Ciência e Técnica  Vitivinícola, 5(1): 25 - 29.
2. FAO/OMS, Commission du Codex Alimentarius, 1982. Doc. CX/EURO 82/3, Partie II, Annexe I, Roma.
3. B. Medina : Dosage du SO2 dans les vinaigres de vin - comparaison de deux méthodes Document OIV, CII-SCMA 03.2006-13.5 - FV 1236