E642 - L-lysine hydrochloride

At a glance

• What it is: the hydrochloride salt of L‑lysine, an essential amino acid the body cannot make.
• What it does: used to fortify foods with lysine; can help smooth taste in high‑protein blends.
• Typical products: protein‑fortified drinks and bars, meal or cereal blends, some seasonings and mixes.
• How it’s made: usually by microbial fermentation of sugars, then converted to the hydrochloride salt.
• Safety: approved for use under food regulations; considered safe when used as intended.
• Label names: “L‑lysine hydrochloride,” “L‑lysine HCl,” or “E642” (EU labelling).

Why is L-lysine hydrochloride added to food?

Manufacturers add L‑lysine hydrochloride to provide a dietary source of lysine, an essential amino acid needed to build body proteins. In the U.S., it is permitted as a nutrient supplement ingredient when used in accordance with good manufacturing practice.¹ In the EU, it appears on the Union list of authorized food additives as E642 with established identity and purity specifications.²

Because amino acids can influence overall taste, L‑lysine hydrochloride may also help round out or soften flavor in protein‑rich or fortified foods, although its primary role is nutrition rather than sweetness or strong “umami” enhancement.¹

What foods contain L-lysine hydrochloride?

You may find L‑lysine hydrochloride in:

• Protein‑fortified beverages and nutrition powders
• Snack bars and cereal blends enriched with amino acids
• Dry mixes, soups, and seasonings where amino acid balancing is desired
• Other fortified foods where lysine is added for nutritional reasons

In the U.S., its use as a nutrient supplement is permitted across food categories when added consistent with good manufacturing practice.¹ In the EU, E642 is listed with specifications in the additive rulebook that governs its identity and purity.²

What can replace L-lysine hydrochloride?

Possible substitutes depend on the goal:

• For taste enhancement in savory foods: monosodium glutamate, disodium inosinate, or disodium guanylate
• For smoothing or rounding flavors in some formulas: glycine and its sodium salt
• For nutrition/fortification: other amino acids or protein ingredients (e.g., whey, soy, pea) to raise overall lysine content

How is L-lysine hydrochloride made?

Commercial L‑lysine is typically produced by fermenting sugars with selected microorganisms; the L‑lysine is then purified and neutralized with hydrochloric acid to form L‑lysine hydrochloride. U.S. food regulations describe manufacturing approaches and require that the final ingredient meet food‑grade specifications and be used under good manufacturing practice.¹ The EU also sets detailed identity and purity criteria for E642 in its specifications regulation.²

Is L-lysine hydrochloride safe to eat?

When used as intended under food laws, L‑lysine hydrochloride is considered safe. In the U.S., it is permitted as a nutrient supplement ingredient in foods, subject to good manufacturing practice.¹ In the EU, E642 is on the Union list of authorized food additives and must meet established purity specifications.² The FDA’s Food Additive Status List also cites the applicable U.S. regulation for L‑lysine monohydrochloride.³

Does L-lysine hydrochloride have any benefits?

Nutritionally, lysine is essential—your body needs it to build proteins but cannot make it on its own. Adding L‑lysine hydrochloride can help foods supply adequate lysine as part of a balanced diet.⁴ Any flavor effects are secondary and are generally mild compared with classic flavor enhancers.

Who should avoid L-lysine hydrochloride?

• People with rare metabolic conditions that affect lysine handling, such as lysinuric protein intolerance (LPI), should follow medical advice about lysine intake and may need to limit it.⁵
• If you are on a medically prescribed low‑protein diet, consult your healthcare professional about amino acid–fortified foods.

Myths & facts

• “It’s the same as MSG.” False. L‑lysine hydrochloride is a lysine salt; MSG is a glutamate salt and works differently in taste.¹
• “It’s animal‑derived.” Generally false. Commercial lysine is commonly made by microbial fermentation, not extracted from animal tissue.¹
• “An E‑number means unsafe.” False. E‑numbers simply indicate an additive has been assessed and authorized for use in the EU, with set specifications.²

L-lysine hydrochloride in branded foods

Check ingredient lists for “L‑lysine hydrochloride,” “L‑lysine HCl,” or “E642.” You’ll most often see it in protein powders and ready‑to‑mix drinks, fortified cereal blends, and some savory mixes where amino acid balance is adjusted.

References

Footnotes

1. 21 CFR 172.320 — L-lysine monohydrochloride and L-lysine monohydrate. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-172/subpart-D/section-172.320 ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

2. Commission Regulation (EU) No 231/2012 — Specifications for food additives listed in Annexes II and III to Regulation (EC) No 1333/2008. https://eur-lex.europa.eu/eli/reg/2012/231/oj ↩ ↩² ↩³ ↩⁴ ↩⁵

3. Food Additive Status List — U.S. FDA. https://www.fda.gov/food/food-additives-petitions/food-additive-status-list ↩

4. Lysine — MedlinePlus (NIH/NLM). https://medlineplus.gov/druginfo/natural/1000.html ↩

5. Lysinuric protein intolerance — Genetic and Rare Diseases (GARD), NIH. https://rarediseases.info.nih.gov/diseases/6730/lysinuric-protein-intolerance ↩