Abstract
(1) Background: most premium red wines are rich in tannins but the effect of chitosan on these macromolecules is unknown. In this work, the effect of a treatment with 0.5 g/L of chitosan on red wines, W, enriched with condensed tannins, CT, ellagitannins, ET, and gallotannins, GT, was evaluated. In addition, to understand if the effect of C was stable during wine evolution, treated wines underwent an oxidative stress simulating an exposure to 18 mg/L of oxygen. (2) Methods: parameters describing the reactivity of phenolic compounds were determined: iron reactive phenolics, BSA reactive tannins, vanillin reactive tannins, and the saliva precipitation index. Individual anthocyanins, total and polymeric pigments and chromatic characteristics were evaluated to determine the influence of each treatment on colour parameters. (3) Results: a decrease in BSA reactive tannins after the addition of C was detected for all wines and the effect persisted after oxidation. W and CT wines previously treated with C and oxidized showed a significant decrease in the reactivity towards salivary proteins. C caused a lower formation of polymeric pigments in all wines. (4) Conclusion: these results suggest a possible use of C to treat wines very rich in condensed tannins and excessively astringent.
Highlights
Sustainability is progressively growing in importance in the wine industry [1,2]
The study of the effect of C on wines containing different oenological tannins is divided in two parts: the first aimed at evaluating the effect of tannins and C addition on phenolic compounds, pigments, and chromatic characteristics of treated wines; the second focussed on understanding if changes detected just after the addition of C persisted after an oxidation treatment aimed at simulating wine evolution
The addition of tannins increased the concentration of total phenols and BSA reactive tannins compared with the control wine
Summary
Sustainability is progressively growing in importance in the wine industry [1,2]. In recent years various industries in oenological products have increased production of new commercial, eco-friendly products, among these, one of the most interesting with characteristics of biocompatibility, biodegradability, and low toxicity is the chitosan C, admitted as a food additive from 2009, (EC) No 606/2009 [3].Chitosan is a natural polysaccharide derived from chitin with polycationic character and a solubility variable in acidic media due to its deacetylation degree and molecular weight [4]. In recent years various industries in oenological products have increased production of new commercial, eco-friendly products, among these, one of the most interesting with characteristics of biocompatibility, biodegradability, and low toxicity is the chitosan C, admitted as a food additive from 2009, (EC) No 606/2009 [3]. The admitted range for the addition of chitosan is 10–500 g/hL according to the aim (Commission regulation (EU)) [5]. Previous studies reported several beneficial effects due to chitosan additions in wine, such as antimicrobial [6,7] and antioxidant activity due to the direct radical scavenging mechanism [8] or indirectly, via metal chelation, which blocks the generation of radical species [9,10,11]. Chitosan is of great relevance because it is effective in controlling B
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