Use of chitosan as a potential antioxidant alternative to sulfites in oenology

In the present PhD thesis work, the efficacy of chitosan, a natural polysaccharide, as a potential antioxidant alternative to the use of sulphur dioxide (SO2) in oenology was studied. For this purpose, a preliminary characterization of the antioxidant properties of chitosan was carried out. Using the Electron Paramagnetic Resonance (EPR) technique, the antiradical capacity of chitosan against hydroxyl (·OH), or 1-hydroxyethyl (1-HER) radicals, was evaluated. On the other hand, by the application of HPLC, the effect of chitosan on compounds related to oxidation, such as glyoxylic acid and acetaldehyde, was studied. Furthermore, indirect antioxidant mechanisms of chitosan, such as capacity of metal chelation, and hydrogen peroxide scavenging were evaluated by flame atomic absorption spectrometry and fluorimetry respectively. The antioxidant activity experiments were carried out both in model and in real wines, showing promising results. Once characterized, winemaking processes in the presence of chitosan were carried out both at micro-scale in the laboratory and at semi-industrial levels, evaluating its effect on the inhibition of browning (abs 420), the total content of polyphenols (abs 280), on organic acids and on the phenolic and volatile profile. For this purpose, chromatography techniques such HPLC-DAD-MS/MS, and GC/MS were used. In addition, sensory analysis with trained panels have been conducted to study the sensory profile of different wines made in the absence of sulfites and in the presence of chitosan, ascorbic acid and glutathione, in order to study the interaction of other well-known antioxidants with chitosan.