L-Cysteine E920
dough conditioner — Primarily synthetic or animal-derived.
L-2-amino-3-mercaptopropionic acid
CAS: 52-90-4
Factual Regulatory Reference
This database provides factual regulatory information compiled from official government sources. It does not constitute medical, nutritional, or safety advice. Regulatory status varies by country and is subject to change. Always refer to your local regulatory authority for the most current information.
What Is L-Cysteine?
L-Cysteine is a sulfur-containing amino acid used as a flour treatment agent and dough conditioner in bread production. It acts as a reducing agent, breaking disulfide bonds in gluten proteins to soften dough and reduce mixing time. It is also used as a flavor precursor in reaction flavors. L-Cysteine is a naturally occurring amino acid in proteins. Commercial production uses fermentation or extraction from natural sources. JECFA considers it acceptable with no ADI specified. EFSA confirmed safety. Approved in EU, USA (GRAS), and other jurisdictions for bakery applications.
? Did You Know?
L-Cysteine occurs naturally in Meat, poultry, eggs and Dairy products. Many people consume it daily without realizing it's also a listed food additive.
L-Cysteine is produced through fermentation — the same biological process used to make bread, beer, and yogurt.
Beyond food, L-Cysteine is also used in cosmetics, medicine, industrial applications, household products. Its versatility makes it one of the most multi-purpose chemical compounds in everyday life.
Regulatory Analysis
The EU's 2004 ban on L-cysteine (E920) as a food additive is unusual in that it was not principally driven by toxicological concerns — L-cysteine is an endogenous amino acid and JECFA found no safety issue. Rather, the EU's position reflected regulatory concerns about the sourcing practices then prevalent: commercial production at the time relied substantially on human hair and poultry feathers, raw materials deemed incompatible with EU food hygiene principles under Regulation (EC) No 852/2004. The FDA and Japan's MHLW maintained approval, treating sourcing as a manufacturing quality matter rather than a regulatory classification question. Industry shift toward fermentation-derived L-cysteine has since reduced the sourcing controversy, yet the EU has not revisited its prohibition, illustrating how regulatory decisions based on production methods rather than substance toxicology can persist even when the underlying manufacturing context changes.
Detailed Regulatory Assessment
European Union (EFSA)
Banned as food additive since 2004
United States (FDA)
Approved as dough conditioner, up to 90 ppm in flour
Japan (MHLW)
Approved as flour treatment agent
Acceptable Daily Intake (ADI)
International Standard (JECFA)
mg/kg body weight per day
European Standard (EFSA)
Everyday Perspective
For a 60kg adult, this limit is roughly equivalent to consuming:
Natural Occurrence
A sulfur-containing amino acid that occurs naturally in proteins. Used in bread-making to break down gluten proteins, making dough more pliable and reducing mixing time.
Manufacturing
Historically extracted from human hair (China) or duck/poultry feathers. Modern production primarily uses bacterial fermentation (E. coli) or chemical synthesis. Hair and feather sources have been phased out in most regions.
Applications Beyond Food
Hair permanents, skin whitening products
Antioxidant supplements, mucolytic agent (N-acetylcysteine)
Flavor enhancer (meat flavoring)
Dietary supplements for skin and hair health