Can fungoid chitosan help to produce sulfite-free wines? Ten years of investigation on its antioxidant properties

Chitosan is a natural polymeric saccharide admitted by EU since 2011 for must and wine clarification, the reduction of some contaminants (e.g. ochratoxin A) and to prevent the development of wine microbial spoilage due to lactic acid bacteria or Dekkera/Brettanomyces yeasts. Scientific evidence is increasingly emerging about additional antioxidant and antiradical features for this polysaccharide when used as adjuvant in food, even if the vast majority of the research was conducted in food systems considerably different from wine for composition, pH and way of utilization. Indeed, the confirmation of such antioxidant activities in a “wine-like” environment would be highly interesting in view of finding a technological tool suitable to vicariate sulfur dioxide and boost the research toward the production of wines with low or nil level of allergenic sulfites. This presentation illustrates the main results obtained in the last decade by our group at the University of Bologna and other colleagues, aiming to evaluate the antioxidant features of fungoid chitosans in model solution and wines, together with the underlying mechanisms involved in these activities. A short overview of the main antimicrobial properties of chitosan will introduce the main subject of the presentation, focused on the physical-chemical mechanisms which govern the antioxidant/antiradical/antibrowning properties of chitosan. The impact of the addition of the polysaccharides on the composition and sensory characteristics of both red and white wines will be also outlined at the light of the technological trials performed at laboratory and industrial scale.