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Cystine
Cystine
Low concern
L-cystine is a naturally occurring amino acid used as a nutrient and dough conditioner. FDA lists L-cystine as GRAS for use as a nutrient and as a dough strengthener in bakery products.
Found in
43 products
What it is
Sulfur-containing amino acid formed from two cysteine molecules.
Nutrient, dough conditioner (in baking), source of sulfur amino acids.
Why it's flagged
- allergen note: often derived from human hair, duck/poultry feathers, or hog hair (sourcing concern for some consumers)
What regulators actually say
"Amino acids... L-Cystine... may be added to foods as nutrients."
"L-cysteine (E920) used as a flour treatment agent... no safety concern at the reported uses."
Regulatory status
United States — FDA
GRAS as a nutrient (21 CFR 172.320) and as a dough strengthener (21 CFR 184.1272 for L-cysteine).
European Union — EFSA
Authorised as food additive E920 (L-cysteine) for flour treatment.
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