E920 L-Cysteine

E920Flour treatment agentsOrigin: Plant or animal

Get a personal answer

Pick your family’s diets in the bar above.

Every diet

VeganDepends

Often from duck feathers or pig hair. Only vegan-certified bread confirms a fermented source.

Gluten-freeNo

Used in wheat bread, so foods containing it usually contain gluten.

HalalDepends

Not halal if made from pig hair.

KosherDepends

Depends on source; feather-derived is accepted by some agencies.

KetoNo

Only used in bread products.

Low-FODMAPNo

Used in wheat bread.

The short answer

L-cysteine (E920) softens dough in bagels and pizza crust. It's often made from duck feathers or pig hair, so it's only reliably vegan or halal when certified.

80/100

Use in moderation

Safe in small amounts; may bother some people or raise blood sugar.

E-numberE920

Comes fromPlant or animal

What it doesFlour treatment agents

Glycemic index—

Daily limitNot set

Also calledL-cysteine, Cysteine

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Plant-based picks

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Certified vegan bagels

Made without animal-derived dough conditioners.

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Unbromated organic bread flour

Bake your own with no conditioners.

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Vegan pizza crust

Certified plant-based crusts.

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Rules by country

🇺🇸 US FDAApproved

🇪🇺 European UnionApproved with limits

🇨🇦 Health CanadaApproved with limits

CaliforniaNo extra rules

Approved as a dough conditioner. The EU allows it only in flour.

Daily limit: Experts haven’t set a number because normal food amounts are far below any level of concern.

What is it?

L-cysteine is an amino acid that relaxes gluten so dough is easier to shape by machine.

Where it comes from: Traditionally made from duck feathers or pig hair. Fermented, plant-based versions now exist but aren't labeled differently.

Why it’s in food

Softens dough for fast machine processing
Shortens mixing time

Often found in

BagelsPizza crustFast-food bunsCommercial bread

Also listed as: L-cysteine, Cysteine, L-cysteine hydrochloride, Dough conditioner

Health & gut impact

SafetyBenefit

An amino acid found in protein foods.

EFSA (2006)

What can I use instead?

Longer kneading and resting

Ratio: N/A

Best for: Home baking

More flour treatment agents:

Potassium Bromate E924Potassium bromate (E924) is a dough strengthener banned in the EU, UK and Canada because it causes cancer in animals. It's still legal in the US; look for "bromated flour."Best to avoid

Common questions

Is L-Cysteine safe?

Use in moderation (80/100). Approved as a dough conditioner. The EU allows it only in flour.

Is L-Cysteine vegan?

Depends. Often from duck feathers or pig hair. Only vegan-certified bread confirms a fermented source.

Is L-Cysteine gluten-free?

No. Used in wheat bread, so foods containing it usually contain gluten.

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Scientific sources & regulatory citations

21 CFR 184.1271 (US FDA)
EFSA OpenFoodTox: E920
EFSA (2006)

Last checked against FDA, EFSA and Health Canada records: October 31, 2026 · INS 920 · CAS 52-90-4