Is L-cysteine (E920) vegan?
Depends — L-cysteine dough conditioner can come from duck feathers, hog hair or fermentation.
Also listed as: E920, cystine
Key facts
- Verdict
- Depends on the brand
- Category
- Additive
- Also listed as
- E920, cystine
- Best swap
- Sourdough breads
Why
The amino acid is used to soften commercial bread and pastry. Traditional production used feathers and hair; synthetic and microbial fermentation versions are now common but rarely labelled.
What to check on the label
- E920 in supermarket bread and buns
- Fast-food bakery items
- Brand confirmation of synthetic source
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What is actually in it
L-cysteine is an amino acid used in baking as a dough conditioner: it breaks the disulphide bonds in gluten, making dough softer, faster to mix and easier to sheet — which is why it appears in commercial bread, pizza bases, bagels, tortillas and some pastries as E920. The controversy is its source. The cheapest industrial route hydrolyses keratin from duck feathers or hog hair, and historically human hair was used in some regions; a second route ferments glucose with engineered bacteria, which can be animal-free; and a third synthesises it from petrochemical feedstocks. All three end up as the identical molecule on the label, with no legal requirement to state the origin — so 'E920' alone tells you nothing. The practical approach: products certified vegan must use the fermented or synthetic form, some large bakeries have publicly committed to feather-free cysteine, and when in doubt the manufacturer can say which source their supplier uses. L-cysteine also turns up in some dietary supplements and flavour production. For home bakers the whole question is avoidable — time is the natural dough conditioner, and long, slow fermentation relaxes gluten the same way without any additives, which is why artisan sourdough never needs E920.
Label codes to recognise
- E920 — L-cysteine
- Feathers, hair, fermentation or synthetic — label does not say
- E921 — L-cysteine hydrochloride
- Same origin question as E920
- Dough conditioner — May include L-cysteine
- Check with manufacturer
Questions people ask
Is bread usually vegan?
Plain bread often is, but soft supermarket buns may contain L-cysteine, whey, honey or mono- and diglycerides.
Can I tell from the label?
Rarely — only a vegan certification or a direct answer from the manufacturer confirms the source.
Is all E920 made from feathers?
No. Feather and hair hydrolysis is one route; fermentation and synthesis are increasingly common, especially in Europe. Only the manufacturer can confirm which source a product uses.
Is L-cysteine in supplements vegan?
Sometimes. Look for 'fermentation-derived' or a vegan logo; otherwise it may come from feathers or hair.
Why is it in bread at all?
It softens gluten so industrial dough mixes faster and machines more easily. Slow-fermented bread achieves the same naturally, which is why artisan loaves skip it.
Is L-cysteine halal or kosher?
It depends on the source — synthetic and fermented forms are generally accepted, hair- and feather-derived forms are contested. Certified products state their source.
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