L-cysteine softens dough and often starts as animal keratin, from feathers or hair. Fermentation-made and synthetic versions are vegan, so it genuinely depends.
Additive codeE920
SourcesFeathers, hair, or microbial fermentation
VerdictSometimes
Where it hides
Commercial bread rolls and bagels
Some pizza and pastry dough
Pretzels and other bakery goods
What it is
L-cysteine is an amino acid used in small amounts to relax dough and speed up baking, listed as E920. The chemistry is the same whatever the origin, and that origin is the whole question. A large share of commercial L-cysteine is extracted from animal keratin, historically duck and chicken feathers and human hair, while a growing amount is made by bacterial fermentation of plant sugars or produced synthetically, both of which are vegan.
Why it depends
Because the label just says L-cysteine or E920, you cannot tell the source from the packet. Some bakeries and brands now specify a plant-based or fermentation-derived version, and the honest answer is that it varies by manufacturer. If it matters to you, this is one to ask about rather than assume.
Bone char sugarSome cane sugar is whitened by filtering it through charred cattle bone. The sugar holds no bone, but the process is animal, so it depends on the brand.
GelatinGelatin is boiled animal collagen, usually from pig or cow skin and bone. There is no plant version; the plant swaps are agar, pectin and carrageenan.
Frequently asked
Is L-cysteine really made from hair?
Some of it is. L-cysteine has long been extracted from keratin sources including human hair and poultry feathers, though fermentation and synthetic routes that are vegan now supply a growing share. The label does not say which, so the source varies by brand.
Which foods contain L-cysteine?
It is a common dough conditioner in commercial bread rolls, bagels, pizza dough and other bakery goods. Home baking and many artisan loaves do not use it.
The sources
What each verdict rests on. Read them yourself.
L-Cysteine (compound summary) · PubChem, US National Library of Medicine (NIH), 2024 · NIH chemical database, identity of the amino acid
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