Effect of chitosan addition on acetaldehyde and polymeric pigments production after oxidation of red wines with different tannin/anthocyanins ratio

In order to evaluate the effect of the application of chitosan to red wines with different initial composition, four wines show ing tannins/anthocyanins ratio (T/A) ranging from 0.15 to 2.44 were treated with this amino polysaccharide. As one of the main factors involved in red wine ageing is the oxidation, even a forced oxidation test was applied on all the samples. The addition of chitosan determined a decrease in total phenolic compounds mainly due to the adsorption of protein-reactive tannins which decreased from 10 to 50% of the initial value. The previous addition of chitosan determined a lower produc tion of acetaldehyde after oxidation confirming the antioxidant activity of this amino polysaccharide. The production of acetaldehyde was lower in samples with a higher T/A ratio probably due to the involvement of acetaldehyde in reactions with flavanols and anthocyanins giving polymeric pigments. These results suggest a possible use of chitosan in red wine with a higher T/A ratio to decrease the content of tannins reactive towards proteins and, contemporary, to act as antioxidant.