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

Laure VATIN1, Roberta BELLINI2, Mattia GHEDIN2, Mirko SOAVE2, Bertrand ROBILLARD1

1 Institut Oenologique de Champagne, EPERNAY, France
2 Perdomini-IOC, VERONA, Italia

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.

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:

Chitosan property
Interaction with transition metals
Interaction with oxidable or oxidized polyphenols
Amino group protonation
Hydrogen bonding and hydrophobic interactions
Direct or undirect radical trapping

Enological applications
Protection against oxidation process
Diminish oxidation potentiality (color and aroma shift)
Flotation and fining properties
Flotation and fining properties
Protection against oxidation process

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.