Chitosan in Food and Packaging – What Really Matters for Function and Application

Chitosan is a versatile biopolymer that is gaining increasing importance in the food and packaging sectors. With its antimicrobial properties, biodegradability, and film-forming capacity, it offers sustainable solutions for shelf-life extension and plastic-free packaging. However, its effectiveness is not determined by degree of deacetylation (DDA) and molecular weight (MW) alone – rather, it results from a combination of chemical and physical characteristics that determine its suitability for different applications.

Chitosan in Food Applications

In food products, chitosan is primarily used as an edible coating – for example, on fruits, vegetables, fish, or cheese. It forms a transparent barrier against moisture and oxygen, exhibits antimicrobial effects, and can inhibit the growth of undesirable microorganisms.

What influences effectiveness in food?

Degree of Deacetylation:
Chitosan with a high DDA (ideally 85–95%) has more free amino groups – these are key to its antimicrobial activity. The positive charge interacts with the negatively charged microbial membranes, leading to growth inhibition.

Molecular Weight:
For edible films, a medium MW (approx. 100–300 kDa) has proven effective: it ensures good solubility, bioactivity, and film-forming ability. Too high a MW may reduce processability, while too low reduces protective performance.

Solubility & pH Dependency:
Chitosan is only soluble in slightly acidic conditions – an optimal pH range is 4.5–5.5. In foods with higher pH (e.g., cheese or meat), this can limit function unless the chitosan is specifically adapted.

Purity / Residual Ash / Allergen-Free:
Strict regulations apply for direct food contact – such as EU Regulation (EC) No. 1333/2008 or FDA approvals. Residual proteins, endotoxins, or heavy metals must be excluded.

Example from research:
In a study by Elsabee & Abdou (2013), chitosan with a DDA of 90% and MW of 150 kDa was used to coat fresh strawberries. The results: significantly delayed mold growth, improved texture, and longer shelf life – with no adverse sensory effects.

Chitosan in Biodegradable Packaging

Chitosan also performs impressively in the packaging industry due to its film-forming ability, barrier properties, and biodegradability. It can be used either as a standalone film or combined with other biopolymers (e.g., gelatin, starch, PLA) to optimize mechanical and sensory properties.

Which properties are decisive here?

Molecular Weight:
For stable packaging films, chitosans with medium to high MW (200–400 kDa) are commonly used. These form stronger polymer networks and improve mechanical performance (tensile strength, flexibility).

Degree of Deacetylation:
A DDA between 80–90% ensures good film-forming capability and simultaneous antimicrobial function. Higher DDA values enhance antimicrobial activity but may reduce film flexibility.

Water and Oxygen Barrier:
Chitosan films provide excellent oxygen barrier properties, but are only moderately water-resistant. This can be improved through chemical modification (e.g., crosslinking or blending).

Combination with Additives:
Chitosan is often combined with active agents such as zinc oxide nanoparticles, essential oils, or bioflavonoids to create active packaging with antimicrobial or antioxidant effects.

Example from research:
Sánchez-González et al. (2011) developed active packaging films using chitosan with a MW of 310 kDa and a DDA of 87%. These films demonstrated excellent oxygen barrier performance, moderate moisture resistance, and strong antimicrobial effects – ideal for packaging cheese or baked goods.

Summary: What really matters

Conclusion
Chitosan is a highly promising, bioactive ingredient for the food sector: edible, antimicrobial, film-forming, and biodegradable. Numerous studies have demonstrated its benefits in edible coatings and sustainable packaging. However, practical implementation is still limited by one key factor: the lack of clear and harmonized regulatory frameworks, particularly regarding direct food applications.

Within the EU: Inconsistent Classification

While chitosan is partially accepted as a processing aid or for use in packaging materials, it is not listed as a food additive (E-number) under EU Regulation (EC) No. 1333/2008. Depending on its source and modification, it may fall under the Novel Food Regulation (EU 2015/2283) and thus require individual approval. In practice, this means: authorization required, but no clear or standardized pathway.

Outside the EU: Mixed Landscape, Slightly More Open

In the United States, chitosan is generally recognized as safe (GRAS) for certain technical applications – but not universally approved for all food uses. In Asian markets such as Japan or South Korea, chitosan is accepted in some forms as a dietary supplement or functional ingredient. However, material purity and source remain critical factors. Globally, no uniform regulatory standard yet exists.

What does this mean for manufacturers?
In practice, companies looking for regulatory clarity and marketing certainty must rely on high-purity chitosan with well-documented specifications – far beyond what is currently required in many loosely regulated markets. This includes standards for purity, heavy metals, microbial load, DDA, molecular weight, and origin.
Because the regulatory framework for food applications remains vague in many regions, high-quality, fully specified chitosan is only selectively adopted in practice – despite strong scientific support for its functionality.

Sources
Rabea, E. I., Badawy, M. E. I., Stevens, C. V., Smagghe, G., & Steurbaut, W. (2003). Chitosan as antimicrobial agent: applications and mode of action. Biomacromolecules, 4(6), 1457-1465.
Elsabee, M. Z., & Abdou, E. S. (2013). Chitosan based edible films and coatings: A review. Materials Science and Engineering: C, 33(4), 1819-1841.
Sánchez-González, L., et al. (2011). Antimicrobial activity of chitosan-based films: influence of polymer molecular weight and deacetylation degree. Carbohydrate Polymers, 84(4), 1040-1047.
Paul, W., & Sharma, C. P. (2004). Chitosan, a drug carrier for the 21st century: a review. STP Pharma Sciences, 14(1), 1-18.
Kumar, M. N. V. R. (2000). A review of chitin and chitosan applications. Reactive and Functional Polymers, 46(1), 1-27.