E920 - l-cysteine

At a glance

• Role: dough conditioner and flour treatment agent that helps with dough handling
• Where found: commercial bread, buns, tortillas, pizza dough, pastries, and some flavorings
• Other names on labels: L-cysteine, L-cysteine HCl, E920
• Usual levels: used under good manufacturing practice (very small amounts)
• Source: made by fermentation or by breaking down keratin-rich materials (such as feathers); the molecule is the same regardless of source

Why is l-cysteine added to food?

L-cysteine is added to improve how dough behaves. It acts as a reducing agent, which helps make dough more extensible and can shorten mixing time. It is also permitted for use as a flavoring agent and adjuvant in foods.¹²

What foods contain l-cysteine?

You are most likely to find L-cysteine in:

• Packaged bread and buns
• Pizza dough and flatbreads (including tortillas)
• Some pastries and croissants
• Certain flavorings and seasonings, where it functions as a flavoring aid

As a flour treatment agent (INS 920), it is used in line with good manufacturing practice rather than at set maximum levels.³

What can replace l-cysteine?

Depending on the product and process, bakers may choose:

• Oxidizing or strengthening agents such as ascorbic acid
• Other dough conditioners like DATEM
• Enzymes, for example alpha-amylase or lipase
• Reducing agents such as sodium metabisulphite
• Texture modifiers like xanthan gum

Choice depends on the flour quality, desired texture, and baking method.

How is l-cysteine made?

Commercial L-cysteine can be produced by:

• Fermentation using microorganisms
• Hydrolysis of keratin-rich materials (for example, feathers or other keratin sources)

Both processes yield the same chemical compound, L-cysteine.² In the European Union, E 920 covers L-cysteine and its hydrochloride, with specifications set for identity and purity.⁴

Is l-cysteine safe to eat?

In the United States, L-cysteine monohydrochloride is affirmed as Generally Recognized as Safe (GRAS) for use as a dough conditioner, nutrient supplement, and flavoring agent, when used in accordance with current good manufacturing practice.¹ Globally, the Codex Alimentarius lists L-cysteine (INS 920) as a flour treatment agent permitted under good manufacturing practice.³ The EU sets official specifications for E 920 (L-cysteine and its hydrochloride), which defines the substance used in foods.⁴

Does l-cysteine have any benefits?

For bakers, L-cysteine can:

• Improve dough handling and consistency
• Help make dough more extensible and reduce mixing time
• Support specific flavor development when used as a flavoring aid

These are recognized food-use functions for L-cysteine/L-cysteine hydrochloride in regulations and technical summaries.¹²

Who should avoid l-cysteine?

• Vegetarians, vegans, and people with religious dietary rules may wish to verify the source (fermentation vs. keratin-derived) with the manufacturer.
• If your healthcare provider has advised you to limit sulfur-containing amino acids for medical reasons, ask whether foods with E920 fit your plan.

Myths & facts

• Myth: “E920 is always made from human hair.” Fact: L-cysteine can be made by fermentation or from keratin sources; the molecule is identical regardless of source.²
• Myth: “E920 is the same as MSG.” Fact: L-cysteine is a different amino acid and serves different functions; in the U.S. it is affirmed as GRAS for use as a dough conditioner, nutrient supplement, and flavoring agent.¹
• Myth: “E920 is a preservative.” Fact: Its primary approved function is as a flour treatment agent/dough conditioner, not as a preservative.³

l-cysteine in branded foods

Look for “L-cysteine,” “L-cysteine hydrochloride,” or “E920” on ingredient lists. It most often appears in mass-produced breads, buns, tortillas, pizza bases, and some pastries. Flavorings may also list it when used as a flavoring aid. If the source matters to you, contact the brand’s consumer line to ask whether their L-cysteine is produced by fermentation.

References

Footnotes

1. 21 CFR 184.1271 — L-cysteine monohydrochloride. ecfr.gov https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-184/subpart-B/section-184.1271 ↩ ↩² ↩³ ↩⁴

2. Cysteine — PubChem Compound Summary (identity, uses such as dough conditioner and flavoring agent; common manufacturing routes). National Institutes of Health. https://pubchem.ncbi.nlm.nih.gov/compound/5862 ↩ ↩² ↩³ ↩⁴

3. GSFA Online: Food additive details for INS 920 (L-cysteine). FAO/WHO Codex Alimentarius. https://www.fao.org/gsfaonline/additives/details.html?ins=920 ↩ ↩² ↩³

4. Commission Regulation (EU) No 231/2012 — Specifications for food additives listed in Annexes II and III to Regulation (EC) No 1333/2008 (includes E 920 L-cysteine). EUR-Lex. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32012R0231 ↩ ↩²