Psychophysical parameters of colour and the chemometric characterisation of wines of the certified denomination of origin 'Rioja'

Colour is one of the most important characteristics of a wine., To measure it, the International Organisation for Wine (OIV) proposes the use of the so-called CieLab parameters: a*, red/green chromaticity; b*, yellow/blue chromaticity; and L*, clarity. However, the need for including the psychophysical parameters: C*, chroma, H*, tone, and S*, saturation has been suggested by some opinions. The six parameters are internationally normalised and they are obtained from the absorption spectrum in the visible range. The aim of this work is to show the interest of the second option through the results of multivariate classification and modelling analysis. The models built with only the three CieLab variables showed to be insufficient for a good characterisation of the colour of the young red wines. When the additional variables C*, H* and S* are introduced, the specificity of the UNEQ models for both categories are improved, from 48 to 70% and from 75 to 81%, respectively. The European Community (EC) has defined claret and rose wines, allowing the consumption of the first only in Spain. In addition, the EC has stated as fraudulent the practice of blending white and red wines to be sold as rose wines. Using wines from the denomination of origin Rioja, the SIMCA models built with the all six variables rejected the blended wines while those built with only three variables did not. (C) 2001 Elsevier Science B.V. All fights reserved.