Is it vegan? Additives & E-numbers E920
Is L-cysteine vegan?
Quick answer: It depends on the source. L-cysteine (E920) is often made from duck feathers or hair, but versions made by fermentation or synthesis are vegan; labels rarely say which.
Also called: E920, cysteine, L-cysteine hydrochloride, flour treatment agent
The details
L-cysteine is an amino acid used mainly as a flour treatment agent to soften dough in industrial bread, bagels and pizza bases, and in some flavourings. It is authorised in the EU and UK as E920.
The Vegetarian Resource Group reports that commercial L-cysteine has most often been derived from duck feathers or human hair, while synthetic and fermentation-derived versions also exist. The label usually does not reveal the source, so the only way to know is to ask the manufacturer or look for a vegan logo.
What to look for on the label
- E920
- L-cysteine
- cysteine hydrochloride
- “flour treatment agent”
Where it’s found
- Industrially made bread, rolls, bagels and pizza dough
- Some savoury flavourings
Vegan alternatives
- Bread with a vegan logo
- Bakery bread made without flour treatment agents
- Ask the manufacturer for fermentation-derived L-cysteine
Frequently asked questions
Is L-cysteine vegan?
It depends on the source. L-cysteine (E920) is often made from duck feathers or hair, but versions made by fermentation or synthesis are vegan; labels rarely say which.
Is E920 always from feathers?
No. It can be produced from feathers or hair, or by fermentation or chemical synthesis. Only the manufacturer can confirm the source.
Is L-cysteine used in UK bread?
It is permitted as a flour treatment agent, but many breads do not use it. Check the ingredients for E920.
Sources
- Approved additives and E numbers — Food Standards Agency (UK)
- Ingredient questions and answers — The Vegetarian Resource Group
- Animal-Derived Ingredients List — PETA
Checked on 31 October 2026. Ingredients and recipes change, and the same product can differ between countries — always check the current label. This page is general information, not allergy or medical advice.