RESOLUTION OENO 5/2008

OENOLOGICAL TANNINS – AMENDMENT TO THE MONOGRAPH

THE GENERAL ASSEMBLY

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

Having studied the research by the "Methods of Analysis" Sub-commission

CONSIDERING resolution Oeno 12/2002 concerning the oenological tannins monograph

DECIDES, upon the proposal of Commission II "Oenology", to supplement resolution Oeno 12/2002 with the addition of point 6.12 as follows:

6.12. Colouring properties

Without prejudice to the provisions of paragraph 1, the use of oenological tannins changes the colour of wines to some extent, depending on their inherent colouring properties. Definitions are therefore required for yellow colouring properties on the one hand (), corresponding to the absorbance at 420 nm of an oenological tannin trial solution of 1‰ dry matter (1g/l). The higher the index, the greater the yellow colour will influence the colour of the wine.

Red colouring properties on the other hand (- ).) correspond to the difference in colouration between the yellow, measured at 420 nm, and the red, measured at 520 nm, of a 1‰ oenological tannin solution: the tannin is colouring agent when the index becomes positive (> ).

Oenological tannins are solubilised in a water/ethanol mixture (50/50 v/v). Absorbences are measured at a 1 cm optical thickness. The measurements are taken immediately after solution treatment. Under these conditions, an oenological tannin should give a clear solution.

The limits of these indices for a oenological tannin not to be considered as a colouring agent are:

• + 1.5 for yellow colouring properties (and
• + 0.05 for red colouring properties (-).