Charge-driven flocculation

Positively charged chitosan can bind to negatively charged particles and colloids. This can destabilise material suspended in the liquid, causing smaller particles to form larger aggregates that may settle or become easier to remove.

This mechanism is central to chitosan’s potential as a clarification or fining aid.

Interaction with microorganisms

Microbial cell surfaces generally contain negatively charged components. Chitosan can bind to these surfaces and may disrupt cell-wall or membrane integrity, affect permeability and interfere with normal cellular activity.

Other proposed mechanisms include interactions with intracellular material and interference with DNA transcription. However, antimicrobial performance varies between organisms and is influenced by pH, molecular weight, concentration and beverage composition.

This is particularly important in brewing: an antimicrobial effect against an unwanted organism does not necessarily mean the same material will leave brewing yeast unaffected.

Metal binding

The amino and hydroxyl groups along the chitosan molecule can interact with metal ions. This gives chitosan the ability to bind metals such as iron, copper, lead and cadmium under suitable conditions.

In beverages, iron and copper are especially relevant because they can contribute to oxidation, haze development and flavour instability. However, the extent to which chitosan removes a particular metal depends heavily on the surrounding chemical environment.

Adsorption of other compounds

Chitosan can also adsorb certain organic compounds and contaminants. The effectiveness and selectivity of this process vary, meaning that removal of an unwanted compound could potentially occur alongside changes to desirable beverage components.

What Can Brewers Learn from Winemaking?

Winemaking provides the clearest commercial reference for beverage applications of chitosan.

In oenology, fungal-origin chitosan is recognised for several purposes, including clarification, the reduction of certain heavy metals and contaminants, and microbial management. It is particularly associated with the control of Brettanomyces, a spoilage yeast responsible for volatile phenols and characteristic medicinal, leathery or barnyard aromas.

Chitosan is also incorporated into some wine-processing formulations intended to support oxidative or microbial stability. This has made it relevant to winemakers seeking additional tools alongside established sulphur dioxide management.

Winemaking demonstrates the broader principle: chitosan’s positively charged structure can be used to manage specific materials or microorganisms when the product, process stage and beverage chemistry are properly matched.

Source Matters

Chitosan may be derived from crustaceans, fungi or other chitin-containing materials. The source can influence purity, composition, regulatory status and allergen considerations.

For oenological use, the International Organisation of Vine and Wine recognises chitosan prepared from food-grade or biotechnological fungal sources, including Aspergillus niger and Agaricus bisporus. This distinguishes it from conventional crustacean-derived chitosan.

Fungal chitosan derived from Aspergillus niger is already permitted in Australia and New Zealand as a processing aid for beer and other alcoholic beverages. FSANZ is also assessing an additional fungal source derived from Agaricus bisporus. Regulatory permission, however, should not be confused with a universally established brewery application. Brewers must still confirm that the specific product and proposed use comply with current requirements.

What Still Needs to Be Understood?

Chitosan is scientifically interesting, but its value to breweries cannot be determined from its chemistry alone. Important practical questions remain:

• Which brewing organisms are affected, and under what conditions?

• At which process stage could it provide the greatest benefit?

• How does it interact with different beer styles?

• Does it affect fermentation performance or yeast recovery?

• What happens to foam, flavour, aroma and mouthfeel?

• Can it improve clarification without removing desirable compounds?

• How does it influence filtration and downstream processing?

• How consistently can it perform at production scale?

• Does it offer a meaningful advantage over established brewing processes?

Answering these questions will require controlled trials, appropriate analytical measurements and sensory assessment. Results from wine, laboratory media or one beer style should not be treated as universal.

A Technology Worth Watching

Chitosan sits at an interesting intersection of beverage chemistry, microbial management and naturally derived processing technology. Its established use in winemaking shows what the molecule can achieve when its chemistry is matched to a clearly defined processing objective.

For now, chitosan is best viewed as a technology worth understanding. As research and commercial experience develop, brewers will be better positioned to decide whether it has a practical role within their own processes.