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E920EmulsifierModerate concern
L-Cysteine
In plain words
The short version
An amino-acid dough conditioner — often derived from animal hair or feathers, creating documented vegan / halal / kosher concerns.
Why we flag it amber
It's permitted and generally considered safe, but there are a few reasons to be mindful — like sensitivities in some people, debated studies, or intake limits. The Safety section below explains the specifics.
Safety profile
ADI not specified — considered safe as a normal dietary amino acid. The safety concern is sourcing rather than the molecule: animal-sourced material is typically not declared by source on labels, conflicting with religious dietary observance and veganism.
The detail
Industrially produced largely by acid hydrolysis of animal feathers or human hair — a fact that creates documented vegan, kosher, and halal concerns. In the EU, the E 920 specification states that human hair may not be used as a source. Microbial fermentation variants exist but are less common. The molecule itself is a normal sulfur amino acid present in all proteins.
Used as a dough conditioner in industrial bread, pizza dough, and bagels at 10–90 mg/kg. Reduces mixing time and improves crumb texture by partially reducing gluten disulfide bonds. Classified as 'Flour treatment agent' in the EU additive system; placed here under Emulsifier alongside other dough conditioners (DATEM, SSL).
White crystalline powder, soluble in water. Free thiol group makes it a strong reducing agent on gluten disulfides.
Permitted globally. EU does not require source disclosure on labels — a frequent point of advocacy for vegan and religious dietary groups.
Sources
- WHO JECFA database — L-Cysteine (flavouring agent, 63rd meeting 2004) — WHO / JECFA, 2004. JECFA: no safety concern; a normal component of protein
- 21 CFR 184.1271 — L-Cysteine (GRAS as dough strengthener) — US eCFR (Office of the Federal Register), 2026. US GRAS dough-strengthener use up to 0.009 parts per 100 parts flour (90 mg/kg)
- EUR-Lex — Commission Regulation (EU) No 231/2012 (additive specifications), consolidated text 18.08.2026 — E 920 — EUR-Lex (European Union), 2026. EU specification excludes human hair as a source
Checked against these sources on .
Educational information only. Not medical, dietary or veterinary advice. Spotted an error? Tell us.