The efficacy of chitosan has been proven, but to understand how this polysaccharide works it is necessary to describe its specific characteristics and mechanism of action.

Chitosan is a natural derivative of biological origin, which is obtained starting from the partial deacetylation of chitin (a polysaccharide composed of N-acetyl-D glucosamine units) in an alkaline environment. To date, the OIV (International Organisation of Vine and Wine) allows the usage of the use of chitosan in oenology for wine processing, or to boost the activity of fining agents in both wines and musts. However only chitosan of fungal origin, and specifically from Aspergillus niger may be used in winemaking.

Research conducted in laboratory on the potential of chitosan is constantly evolving and shows surprising results; indeed, chitosan is an element which, in addition to having proven efficacy and versatility of use, also stands out because it is easily available and biodegradable.

Use and action of chitosan in musts and wines

Chitosan is a valuable support to facilitate the racking and clarification of musts. It also has an important antiseptic action by inhibiting microbiological activity.

Used in wines, chitosan promotes clarification and inhibits unwanted fermentations, which would have a negative impact on the entire process. Furthermore, it prevents the development of acetic bacteria, which are responsible for raising volatile acidity, or malolactic fermentation, where unwanted.

Another important function of chitosan is the removal of metal cations from the solution, which, reduces the content of heavy metals such as iron, lead, cadmium and copper.

On the one hand, this type of action allows avoiding copper and iron instabilities, on the other, it further destabilizes the microbial wall by removing structural cations.

In addition, it reduces any unwanted compounds such as ochratoxin A, a fungal toxin that can be found following microbial alterations in grapes. But what makes chitosan the polysaccharide of choice in oenology is its ability to inhibit Brettanomyces: against these contaminating yeasts, in fact, chitosan serves as an indispensable adjuvant and its use allows achieving incomparable results compared to other products.

The antiseptic action of chitosan against Brettanomyces

As discussed before, the most important and widespread use of chitosan in oenology relates to the inhibition of Brettanomyces, where no other adjuvant is able to perform such an effective action.

Brettanomyces is a contaminating yeast, which is particularly resistant to high levels of ethanol and can catalyse the reduction of vinylphenols through the enzyme vinylphenol reductase. This type of biocatalytic activity is responsible for the onset of olfactory defects such as the scents of “stable”, “leather” and “horse sweat”.

We need to examine the structure of chitosan in order to explain how it acts against the onset of Brettanomyces.

Indeed, we know that chitosan is obtained from the partial deacetylation of chitin, during which the release of the primary amino groups occurs, which, in an acid environment, are protonated, thus yielding a positive charge.

This particular type of charged structure is functional to the disintegration of the membranes of bacteria and yeasts. In fact, one of the mechanisms by which chitosan acts results from the fact that the outside of the cell wall for bacteria is negatively charged and, therefore, being positively charged, acts by complementary charge. On the other hand, yeasts do not have an obvious negative charge, but it is thought that they incorporate chitosan into their own wall during growth, thus leading to wall disintegration. An alternative mechanism of action can be traced back to the binding of chitosan to microbial DNA, which would effectively block DNA transcription and replication.

Chitocel, the chitosan-based AEB solution

CHITOCEL is a chitosan-based product, a natural polysaccharide of fungal origin (Aspergillus niger) which allows reducing, and, in some cases, eliminating, any unwanted microbial load in wine. It is active against acetic and lactic bacteria, yeasts in general and Brettanomyces.

The special and balanced formulation with yeast hulls allows CHITOCEL to exert a broad-spectrum antimicrobial action, thus contributing to aromatic and olfactory cleansing. 

CHITOCEL is widely used in wines to be aged in wood: indeed, the porosity of wood is the ideal environment for the development and growth of microorganisms (and Brettanomyces in particular), which, although present in modest quantities, in the long-medium term can increase volatile acidity and often generate unpleasant odours.

In addition, CHITOCEL has the advantage of not belonging to the family of allergens, like other similar products that, among other things, exert an antimicrobial activity only on some families of bacteria and can contribute to increasing protein instability.

How does Chitocel work?

We explain how CHITOCEL works through a practical test carried out in the laboratory: we used a wine contaminated with Brettanomyces to evaluate the efficacy of CHITOCEL in a quantity of 5 g/hL. Even before completing a microbial count, we verified the activity of chitosan under the microscope on the contaminating yeast, and confirmed the destruction of cellular integrity.

Subsequently, in order to perform a plate count, we filtered a 50 mL aliquot of the solution on a membrane with a porosity of 0.2 µm, and then incubated it for 8 days at 30°C on a selective medium for Brettanomyces.

Alongside CHITOCEL we have developed other chitosan-based products, which represent excellent alternatives to SO₂:

• CHITOCEL Must, which is ideal for use in white winemaking, protects the wine from early alterations, and its co-formulation with tannic acid serves as antioxidant by acting in a manner akin sulfur dioxide and can replace SO₂;
• CHITOCEL Red on the other hand, is particularly suitable for the production of red wines. It allows stabilising the colour and correcting any defects; in addition, it performs the same action as sulfur dioxide thanks to the combination of chitosan and proanthocyanidin.

CHITOCEL Must and CHITOCEL Red exert a clarifying action, contribute to the reduction of the content of heavy metals such as iron, lead, cadmium and copper, thus preventing iron and copper instabilities, and allow reducing any contaminants (such as ochratoxin), thanks to the synergy with yeast hulls and tannins.

Therefore, both have antimicrobial properties and allow limiting the use of sulfur dioxide, in line with growing market demands which, in recent years, have been calling for products with ever lower sulphite contents.

The range is completed with ANTIBRETT 2.0 and CHITO-F.

ANTIBRETT 2.0 is a product combining chitosan, yeast hulls and beta-glucanase enzymes, which is particularly suitable for its inhibitory action against yeasts belonging to the Brettanomyces genus.

In fact, thanks to its antimicrobial properties, it inhibits the production of vinyl reductase, which participates in the transformation of cinnamic acids naturally present in wines, into the corresponding ethyl derivatives, responsible for the odours attributable to Brettanomyces.

ANTIBRETT 2.0 is indicated both to prevent alterations due to unwanted yeasts, and as a curative product: indeed, Brettanomyces has very long incubation times (3-8 months), during which there are no abnormal odours; therefore, its use may be required after any such odours are detected.

CHITO-F, on the other hand, is a new specific treatment based on fumaric acid and chitosan. It exerts a strong antimicrobial, bacteriocidal and bacteriostatic action, stabilizes and promotes wine clarification.

At the origin of CHITO-F is the growing trend toward natural, sulfur-free products for wine production, and a market increasingly interested in beverages with reduced sulfite contents.

Because of its potent antimicrobial action resulting from the synergy of components, it allows the use of lower amounts of SO₂, protecting wines and thus representing an allergen-free alternative to stabilizers that perform the same function.

CHITO-F also plays an important role in the prevention and treatment of contamination due to lactic acid bacteria, facilitating work in the winery.

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