Colour and pigment composition of red wines obtained from co-maceration of Tempranillo and Graciano varieties

The Vitis vinifera L. cv Graciano is often used as an integral component of Rioja wines because it is considered to contribute significantly to the quality of Tempranillo based wines. The aim of this work was to determine the effect of the incorporation of the Graciano variety on the colour and pigment composition of Tempranillo based wine and to evaluate the possible differences between blending Tempranillo with Graciano varietal wine ( W wine) in contrast to a wine obtained by mixing these two grape varieties in the prefermentative maceration step ( M wine). Results indicated that pigment extraction and retention in M wine was higher than in Tempranillo ( T) wine. Colour differences ( Δ E ab * ) between wines at the end of the study (after 12 months in bottles) were detectable by the human eye ( Δ E ab * ≥ 3) in all cases except for T and W. These wines have indistinguishable colours even when using analytical methods ( Δ E ab * ≤ 1). Regarding hue h ab, T and W presented higher values (more orange-red) than Graciano ( G) and M (more blue-red). PCA allowed the colour and composition analytical data to be reduced to a small number of principal components that could separate successfully between T and G wines and between the different steps of the winemaking process.