Inhibitory effect of fungoid chitosan in the generation of aldehydes relevant to photooxidative decay in a sulphite-free white wine.

The reaction pathways were investigated by which a fungoid chitosan (CsG) may protect against photooxidative decay of model solutions and a sulphite-free white wine. Samples containing CsG were dark incubated for 2 days before exposure to fluorescent lighting for up to 21 days in the presence of wine like (+)-catechin and/or iron doses. In both systems CsG at winemaking doses significantly reduced the photoproduction of acetaldehyde and, to a better extent, glyoxylic acid, two key reactive aldehydes implicated in wine oxidative spoilage. After 21 days, CsG was two-fold more effective than sulphur dioxide in preventing glyoxylic acid formation and minimizing the browning of white wine. Among the antioxidant mechanisms involved in CsG protective effect, iron chelation, and hydrogen peroxide quenching were demonstrated. Besides, the previously unreported tartrate displacement from the [iron(III)-tartrate] complex was revealed as an additional inhibitory mechanism of CsG under photo-Fenton oxidation conditions.

Relevance and perspectives of the use of chitosan in winemaking: a review.

Chitosan is a natural polymer that has quite recently been approved as an aid for microbial control, metal chelation, clarification, and reduction of contaminants in enology. In foods other than wine, chitosan has also been evidenced to have some other activities such as antioxidant and antiradical properties. Nevertheless, the actual extent of its activities in must and wines has not been fully established. This review aimed to gather and discuss the available scientific information on the efficacy of chitosan as a multifaceted aid in winemaking, including antimicrobial, chelating, clarifying and antioxidant activities, while summarizing the chemical mechanisms underlying its action. Attention has been specifically paid to those data obtained by using unmodified chitosan in wine or in conditions pertinent to its production, intentionally excluding functionalized polymers, not admitted in enology. Unconventional utilizations together with future perspectives and research needs targeting, for example, the use of chitosan from distinct sources, production strategies to increase its efficacy or the potential sensory impact of this polysaccharide, have also been outlined.

Chitosan in Sparkling Wines Produced by the Traditional Method: Influence of Its Presence during the Secondary Fermentation.

Chitosan is a polysaccharide admitted in winemaking as clarifying, antimicrobial and chelating agent. In addition, evidence about its antioxidant and radical scavenging activities have been recently reported in wine conditions. As an insoluble adjuvant, chitosan efficacy also depends on the duration of its contact with the matrix. In the case of sparkling wines obtained following the traditional method, for instance, the addition of chitosan before the secondary fermentation would permit a prolonged contact of the polymer with wine and yeast lees. However, information on the effects of this practice on final products is totally unknown. In this work, the addition of chitosan during the secondary fermentation of a traditional sparkling wine production method has been investigated for its effects on both the physicochemical and sensory characteristics of the resulting wine. After 12 months of "sur lie" maturation, chitosan was found to increase the protein and amino acid content of wines up to about 50% and 9%, respectively, with limited change of phenolics and organic acids. Volatile compounds, particularly esters, were increased as well, which was reflected by higher values for fruity character and aroma intensity after sensory tests. Foaming features, evaluated by sensory and physical measurements, were also positively affected.

Chitosan as an antioxidant alternative to sulphites in oenology: EPR investigation of inhibitory mechanisms.

The efficacy against oxidative degradation in model and sulphite-free white wines of two commercial, insoluble chitosans (one being approved for winemaking) were investigated by electron paramagnetic resonance (EPR). Both compounds at various doses significantly inhibited the formation of α-(4-pyridyl-1-oxide)-N-t-butylnitrone (4-POBN)-1-hydroxyethyl adducts under normal wine storage conditions. Pre-incubation with 2 g/L chitosan followed by filtration had a better effect than adding 50 mg/L sulphur dioxide to the experimental Chardonnay wine on the release of 4-POBN adducts after 6 days of incubation with 100 µM iron(II). In a relevant photooxidative system acetaldehyde formation was significantly reduced after 6 days of incubation. Parallel EPR tests were performed to assess the importance of metal chelation (iron and copper) versus direct scavenging of hydroxyl radicals on the effect of chitosan. The present data support the potentiality of using biocompatible chitosan as a healthier complement and/or alternative to sulphur dioxide against white wine oxidative spoilage.