Binding capacity of brown pigments present in special Spanish sweet wines

Some special Spanish sweet wines are obtained by addition of a sweetening and coloring agent called grape syrup, which is obtained by heating must to give a dark and highly caramelised liquid, with similar consistency than other syrups. The aim of this work was to establish the influence of the addition of boiled must or “grape syrup” on the aroma and colour of sweet wines focussing specially on the possible binding effect on volatile compounds. The influence of must polyphenols was also studied, so, a wine sweetened with a “grape syrup” free of polyphenols was also elaborated. As it was expected, the addition of grape syrups gave an increase in the levels of furfural related compounds, and sweet wines showed lower concentrations of terpenes, ethyl esters, organic acids and acetates of alcohols than the control wine. The capacity of brown polymers present in grape syrups to bind these volatile compounds is discussed. Furthermore, colour parameters were also studied and significant differences were found for all of them between sweet wines and control wine.