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Reducing the use of chemicals in winemaking: strategies involving the use of chitosan for purposes other than microbial control

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Tuesday 18th May

Fungal-origin chitosan in winemaking for purposes other than microbial control

Bertrand Robillard, Institute Oenologique de Champagne, France

Chitosan is extracted from chitin, the 2nd most represented polysaccharide on Earth after cellulose. We find this biopolymer distributed in Nature through the exoskeletons of crustaceans but also from mushrooms like Agaricus or Aspergillus. For more than 10 years now, the OIV has recommended the use of chitin derivatives (chitosan and chitin-glucan) in oenology, only from fungal origin to avoid any allergenic risk.

As can be seen below, the skeleton of chitosan is identical to that of cellulose and differs from it only by the presence of an amino group instead of a hydroxyl group.

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This minor difference is sufficient to confer on this biomolecule very broad properties which allow its use in many of the heavy industries as a flocculant in wastewater treatment, as a metal cation trapper, but also in finer applications: cosmetic or pharmaceutical fields as bacteriostatic, or in food-processing for food preservation.

The enological world took advantage of this unique properties of chitosan for different applications on must or wine. The reputation of chitosan has essentially been built around its particularly effective action to fight against microbiological drifts. For instance, some wines particularly contaminated with Brettanomycès may recover their population below the detection threshold after a few weeks of treatment at a dosage ranges from 40 to 50mg/L.

Other applications of this biopolymer in oenology are more recent or still unknown and deserve to be detailed.

In this communication, we propose first to summarize the hypothetical or demonstrated mechanisms that explain the interactions between chitosan and various elements that may be present in juice or wine. In 2nd, we show the applications of these mechanisms in real cases, through various examples that can be summarized as below:

The examples will be illustrated with sensory analysis results showing that chitosan is a fining agent which respects the wine quality.

It is thus shown that chitosan is a biopolymer increasingly used in oenology because it meets a strong client/consumer demand, namely the use of non-animal, non-synthetic, non-allergenic inputs and offers a wide range of enological applications from the must to finished wines.

 

Chitosan in oenology: a rapid and innovative analysis to ensure its origin as a fungus

Matteo Perini, Fondazione Edmund Mach

Chitosan is a linear polysaccharide used in oenology for microbiological control, reducing the use of sulphites, chelating heavy metals and as an antioxidant and clarifier in musts and wines.

The food additive is commonly produced by chemical deacetylation of chitin extracted from the exoskeleton of different types of crustaceans such as shrimp. These can cause severe allergic reactions such as anaphylaxis and the chitosan produced from these crustaceans could in turn cause allergic phenomena due to the presence of protein residues (such as tropomyosin) that are released after ingestion of the product. For this reason, in recent years the production of chitosan from fungal fermentation has received great attention, so much so that it has become the only type allowed for oenological use by the International Organization of Grapes and Wine (OIV). The official methods prescribed to confirm the fungal origin of chitosan (residual glucan content, viscosity in 1% solution and beaten density). For this reason, we considered it necessary to develop a new, fast and more automated analytical method based on the analysis of stable isotope ratios. In this study, 35 different chitosan samples of fungal origin or animal exoskeleton were considered and the isotope analysis of the hydrogen, oxygen, carbon and nitrogen ratios was performed.

The Kruskal-Wallis test showed that the isotope ratio of carbon (δ13C) and oxygen (δ18O) turns out to be the most significant parameters (p <0.0001), while a partial least squares discriminant analysis (PLS-DA) has a correct classification of the sample in 100%.

The results obtained show how this new method is able to identify with certainty the fungal origin of the chitosan used in oenology.