Definition
Chitin is a tough, fibrous natural polymer that forms the cell walls of fungi and the shells of insects and crustaceans, making raw mushrooms hard to digest.
Chitin is a strong, fibrous natural polymer that gives structure to the cell walls of fungi and to the exoskeletons of insects, crabs, shrimp and lobsters. It is made of long chains of a modified sugar called N-acetylglucosamine, and after cellulose it is one of the most abundant natural polymers on Earth.
Chitin in mushrooms
In fungi, chitin is woven together with beta-glucans and proteins to form a sturdy cell wall. This is one of the key differences between fungi and plants, which build their cell walls from cellulose instead, and it is part of why mycology classifies fungi as a separate kingdom. The amount of chitin varies by species: soft culinary mushrooms have relatively little, while woody conks such as reishi and chaga are tough and dense.
Why chitin matters in the kitchen
People do not digest chitin efficiently. That is one reason many cooks recommend thoroughly cooking mushrooms rather than eating them raw, and why tough species are simmered rather than chewed. Cooking softens the texture and makes mushrooms more pleasant to eat.
Why chitin matters for extracts
Chitin is the main reason mushroom extracts exist. Long simmering in hot-water extraction, sometimes followed by an alcohol step in dual extraction, helps release the compounds that are locked inside the chitin-rich cell wall. The spent, fibrous material is then filtered away.
Other uses
- Chitosan: a softened form of chitin, made mainly from crustacean shells, used in water filtration, food packaging films and wine clarification.
- Materials science: researchers explore chitin for biodegradable plastics and textiles.
- Allergen note: shellfish-derived chitosan is labeled carefully because of shellfish allergens; fungal chitin comes from a completely different source.
From cell walls to confections
Understanding chitin explains why functional mushrooms are usually used as powders or extracts in foods like chocolate. See how Polkadot pairs a functional mushroom blend with Belgian chocolate in What Is Functional Mushroom Chocolate?
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