The use of chitosan to control (+)-catechin oxidation: hypothesis for its use in reduced sulfur dioxide winemaking practices

Chitosan is an additive used in the food industry thanks to its proven anti-microbial, chelating and anti-oxidant activities. In 2011, the EU inserted chitosan to the list of additives permitted for use in winemaking practices to stabilize proteins, for microbial control and for the reduction of contaminants and heavy metals. However, even today, there are few studies with regards to the antioxidant capacity of this molecule in matrices similar to wine. In this study the efficacy of chitosan, in controlling the oxidation of (+)-catechin in a synthetic white wine under notable oxidative conditions, was tested and compared to that of sulfur dioxide, glutathione and ascorbic acid. The formation of intermediate oxidation compounds was determined using chromatographic HPLC-DAD-MS analyses and spectrophotometry. The results showed that chitosan had a notable capacity to delay the oxidative degradation of (+)-catechin and that this phenomena can be the result of mechanisms that involve the chelation of metals, the absorption of intermediate molecules and an anti-radical activity. The presence of chitosan also contributed to limit the oxidation of the thiol components found in the model solutions tested in this study. Based on the results obtained it is possible to propose chitosan as a potential additive capable to complement or substitute sulfur dioxide in winemaking processes aimed at reducing the sulfite content of white wines.