Assessment of chitosan extracted from different sources for controlling undesirable yeasts in low-sulphite wine production

The use of sulphur dioxide (SO₂) is a well-established practice in winemaking due to its antimicrobial and antioxidant properties. However, concerns about its potential negative effects on consumer health and the sensory properties of wine are driving the search for alternative solutions. Chitosan, a natural polysaccharide obtained from the deacetylation process of chitin, has gained interest. The International Organisation of Vine and Wine (OIV) has already authorised the use of chitosan from Aspergillus niger, but other sources of chitin are available, such as insects, which offer a sustainable alternative. This study explores the potential use of chitosan from insects (Hermetia illucens) as an innovative strategy to reduce or replace SO₂ in winemaking. The first phase of the research evaluated the antimicrobial activity of insect-based chitosan against non-Saccharomyces yeasts commonly found during fermentation (Metschnikowia pulcherrima, Candida zemplinina, Hanseniaspora spp, Torulaspora delbrueckii, Zygosaccharomyces bailii, Lachancea thermotolerans and Pichia spp.). These yeasts can influence fermentation kinetics and wine quality, and controlling their proliferation is essential to prevent unwanted fermentations. Non-Saccharomyces yeasts showed medium-high resistance to chitosan, observing a strain-dependent sensitivity. Furthermore, the combined use of chitosan and low doses of SO₂ was more effective than chitosan alone, suggesting its potential role in sulphite reduction. The second phase investigated the efficacy of insect-based chitosan against Brettanomyces bruxellensis, a spoilage yeast. Through resistance tests, flow cytometry and microscopic observations, it was shown that insect-based chitosan effectively reduced B. bruxellensis populations, showing a greater impact than oenological chitosan from A. niger. This suggests that insect-based chitosan could be a valuable tool for wine stabilisation, particularly during barrel ageing.