L-Cysteine
Also known as: E920, L-cysteine hydrochloride, L-2-Amino-3-mercaptopropionic acid, L-Cys, (R)-2-Amino-3-mercaptopropanoic acid
L-Cysteine is a naturally occurring amino acid used in flour at very low levels (FDA limit 0.009% of flour). It is approved by FDA (21 CFR 184.1271) and EFSA.
What it is
L-Cysteine — a sulfur-containing amino acid, used in food typically as L-cysteine hydrochloride.
Flour treatment / dough conditioner; speeds gluten development; also used as a flavor precursor.
Why it's flagged
- sourcing transparency (hair/feathers) — non-safety concern
What regulators actually say
"L-cysteine monohydrochloride is generally recognized as safe... Used as a dough strengthener to supply up to 0.009 part of total L-cysteine per 100 parts of flour."
"EFSA opinion on the use of L-cysteine in foods intended for infants and young children."
Regulatory status
United States — FDA
GRAS as dough strengthener up to 0.009% of flour (21 CFR 184.1271)
European Union — EFSA
Authorized as E 920
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