Chitosan as an alternative to SO₂ in winemaking: A preliminary trial

Abstract

Sulphur dioxide is the most widely used additive in winemaking because of its antimicrobial and antioxidant properties. However, consumer demand for healthier and more natural products, together with increasingly restrictive legislation, has made reducing or eliminating SO₂ a major challenge. Chitosan is a natural product with antimicrobial and antioxidant activity. This preliminary study compared Tempranillo wines produced with 50 mg SO₂/kg, 400 mg chitosan/kg, or a combination of 25 mg SO₂ and 200 mg chitosan/kg, with three replicates per treatment. After winemaking, standard OIV physicochemical parameters, nitrogen fractions, total phenols and anthocyanins, colour parameters and CIELab coordinates were analysed. Fermentation initially progressed more slowly in wines in which SO₂ was replaced by chitosan, probably because of its antimicrobial activity, but all yeasts completed fermentation at approximately the same time. Malic and lactic acid concentrations were higher in chitosan-treated wines than in the control, although total acidity did not differ among treatments. Ammonium nitrogen was also higher with chitosan, while amino nitrogen and yeast-assimilable nitrogen were unaffected. Wines receiving the combined treatment contained more total phenols than either control or chitosan-only wines. The results indicate that chitosan could help replace or reduce SO₂, since the analysed parameters were maintained or improved compared with conventional winemaking.

References

1. Romanazzi G, Feliziani E and Sivakumar D. (2018). Chitosan, a biopolymer with triple action on postharvest decay of fruit and vegetables: eliciting, antimicrobial and film-forming properties. Front Microbiol 9:2745.
2. OIV, 2021: Compendium of International Methods of Wine and Must Analysis International Organisation of Vine and Wine, París, Francia.

Acknowledgements

The authors thank the Institute of Rioja Studies of the Government of La Rioja for funding project No. 00860-2022/123783. E.P. Pérez-Álvarez thanks the Spanish Ministry of Science and Innovation for her Ramón y Cajal contract (RYC2022-036443-I).