A review of the current knowledge of red wine colour.
2017
Victor Armando Pereira de Freitas | Ana Fernandes | Joana Oliveira | Natércia Teixeira | Nuno Mateus
Anthocyanins are the main compounds present in young red wines, being responsible for their intense red colour. These pigments are mainly located in grape skins and their extractability during winemaking depends on many factors, such as their concentration in vacuoles and interaction with the cell-wall polysaccharides, affecting their stability and concentration in the must. The red colour of anthocyanins at wine pH is explained by the stabilization of the flavylium cation form that displays a red colour; otherwise at this pH the hemiketal colourless is the dominant form, bleaching the wine. Besides the contribution of free anthocyanins, a phenomenon called copigmentation influences the colour of young red wines. Copigmentation can be defined as a series of stabilization mechanisms involving van der Walls interactions that occur naturally in red wines and that can explain this unanticipated colour behaviour. Copigmentation is also pointed as the first interaction between anthocyanins and other wine components leading after that to the formation of new coloured compounds during red wine ageing. Some of these pigments have already been identified and characterized but many are still undiscovered. The detection and structural characterization of new pigments, and the knowledge of their chemical formation pathways are crucial to better understand the evolution of the colour of red wine during ageing.
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