Changes in colour and phenolic composition in sweet red wines made from Merlot, Syrah and Tempranillo
grapes were studied in order to assess the influence of bottle storage over a period of 12 months. For
this purpose, wine colour parameters, sensory analysis and concentrations of monomeric anthocyanins,
pyranoanthocyanins, methylmethine-mediated condensation adducts, flavan3-ol derivatives and flavonols
were measured. Hue increased and red colours decreased with the storage time, particularly over
the first 3 months. The concentrations of low molecular weight flavan-3-ol derivatives decreased with
time due to the effect of their conversion into tannins of high molecular weight. In addition, the glycosylated
flavonols decreased through hydrolysis to give the corresponding aglycones. Overall, the concentration
of phenolic compounds decreased markedly with storage time, whereas the antioxidant activity in
the wines remained constant throughout. A panel of expert tasters judged the colour, aroma and flavour
of all initial and final wines to be acceptable.