Abstract
Chitosan is a natural biopolymer, which is gaining interest in red winemaking thanks to its ability to inhibit the development of Brettanomyces spp. yeast, or other undesired wine microbial threats. However, little is known about potential side-effects of its addition on the physico-chemical parameters of red wines. To fill the gap on this aspect, this work focused on changes in color, phenolic and volatile composition of red wines treated for 7 days with 0.5 g/L of fungoid chitosan, added in both undissolved and dissolved form. When compared to untreated samples, minor changes in phenolic compounds were observed in chitosan added wines, mainly involving hydroxycinnamic acids and flavonols, with reductions of 3 mg/L and 1.5 mg/L respectively. Ellagic acid, however, was absorbed up to 2 mg/L, which reduced his content by 40%. Since some of these compounds actively participate to co-pigmentation with anthocyanins, the color of wines was influenced accordingly. Chitosan marginally absorbed some aroma compounds, including volatile phenols whose amounts were slightly but significantly decreased after treatment. Overall, at the dose adopted, chitosan appeared suited to be used in red winemaking for microbial or physical stability purposes, not severely impairing the quality parameters of the final wines.
Highlights
Chitosan is a biopolymer made of 2-Amino-2-deoxy-poly-d-glucosamine and N-acetyl glucosamine which is obtained from the deacetylation of chitin extracted from sources such as fungi, crustaceans, insects [1]
Our results revealed that the presence of chitosan affected to a greater extent the amount of hydroxycinnamic acids by reducing preferentially the concentration of caffeic acid derivatives and coumaric acid, reaching removal levels up to 1.22 mg/L and 0.89 mg/L
The overall results showed that post fermentation fining of red wines with chitosan up to 500 mg/L
Summary
Chitosan is a biopolymer made of 2-Amino-2-deoxy-poly-d-glucosamine and N-acetyl glucosamine which is obtained from the deacetylation of chitin extracted from sources such as fungi, crustaceans, insects [1]. Chitosan is able to inhibit the growth of a wide range of spoilage microorganisms such as acetic acid bacteria, lactic acid bacteria and Brettanomyces spp. yeasts [5,6,7]. These latter are spoilage yeasts responsible for the production of volatile phenols (4-ethyl phenol and 4-ethyl guaiacol) and the consequent development of the “horse sweat”, “smoky” and “leather” character in wood aged or stored red wines, which are severely compromised in quality. Already published results confirm that in red wines, the presence of 4–8 g/hL chitosan for 6–10 days can effectively prevent the microbial developments, avoiding the risk of the mentioned sensory defect [5,8]
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