Effects of pH, sulphur dioxide, alcohol content, temperature and storage time on colour composition of a young Portuguese red table wine

In a young Portuguese red table wine (Douro Valley) a significant relationship between the colour composition (anthocyanins, polymeric pigment, colour density) and five parameters (pH, SO2, alcohol, temperature, time of storage) were found. Higher temperature increased the loss of individual and total anthocyanins (as measured fay HPLC) during the ageing, while the wines with higher SO2 content contained a greater amount of anthocyanins. Malvidin 3‐glucoside acetate was the only anthocyanin not affected by the SO2 content, but its concentration was related with the interaction term (time of storage × SO2 content). Peonidin and malvidin 3‐glucoside‐p‐coumarate were the two anthocyanins affected by the quadratic term of temperature. Three different groups of equations corresponding to the three different states of the glucoside moiety were found. The polymeric pigment absorbance increases daring conservation and with higher temperature, while the pH and SO2 content decreased the polymeric pigment formation. The colour density of the experimental wine was related significantly to the changes of the coloured anthocyanins and to the polymeric pigment content.