L-Lysine Hydrochloride

Grades and forms of L-lysine HCl powder

L-lysine HCl is the monohydrochloride salt of the amino acid L-lysine, with a molar mass of 182.65 g/mol. It is the lysine form most supplement manufacturers buy for capsules, tablets and powders. The salt is easier to handle than lysine free base, which takes up moisture readily.

Food supplement manufacturers buy L-lysine HCl as food grade or as a grade tested to a pharmacopoeia monograph. Feed-grade lysine HCl is also widely traded but is not intended for human food. Purchase specifications should therefore name the grade explicitly.

The choice of grade usually follows the brand’s quality system and target market:

• Pharmacopoeia grade suits brands that release raw materials against a monograph.
• Food grade covers most food supplement work.
• Finer powders blend and dissolve well. Coarser or granulated material flows better on tablet presses.

The specification sheet states the assay, particle size and other parameters for each grade. SoleChem sends it with the certificate of analysis when it quotes. State the grade and particle size you need in the quote form.

L-lysine HCl is generally produced by bacterial fermentation. If your QA team needs information on the fermentation substrate or production strain, list it in the request.

EU regulatory status

Directive 2002/46/EC sets composition rules only for vitamins and minerals in food supplements. Annexes I and II of Directive 2002/46/EC list those nutrients and their permitted forms, and amino acids are outside their scope. Our guide to permitted vitamin and mineral forms explains how the annexes work.

The use of L-lysine HCl in food supplements therefore falls under national rules on “other substances”. These differ between member states. Some keep positive lists, notification procedures or national maximum amounts; others rely on general food law. Check each target market with its competent authority.

Regulation (EC) No 1925/2006 lets the Commission restrict or prohibit other substances through Article 8 and Annex III. Confirm before launch that no such measure covers lysine. Confirm the novel-food position under Regulation (EU) 2015/2283 as well; our novel food guide sets out how to check.

On the label, Directive 2002/46/EC requires the amount of each substance with a nutritional or physiological effect per recommended daily portion, in numerical form. General rules come from Regulation (EU) No 1169/2011; see labelling a food supplement in the EU. Any claim must comply with Regulation (EC) No 1924/2006. Check the EU Register of nutrition and health claims and our health claims guide.

Formulation notes

L-lysine HCl dissolves readily in water. That suits drink powders, sachets and effervescent tablets. Its taste is bitter and slightly salty, so flavoured powders and chewables usually need masking.

Lysine carries a free amino group on its side chain. This group reacts with reducing sugars such as glucose, fructose and lactose in the Maillard reaction. The result is browning and loss of lysine in storage, faster with heat and moisture. It matters in gummies made with glucose syrup and in tablets with lactose fillers. Non-reducing fillers such as microcrystalline cellulose or dicalcium phosphate avoid the reaction.

In capsules, high label claims fill the shell volume quickly. The bulk density on the specification sheet decides which capsule size a claim needs. In tablets, crystalline grades often need granulation or a direct-compression excipient, and a glidant such as silicon dioxide can improve flow.

L-lysine HCl is often blended with other amino acids such as L-arginine. Check the combined chloride and taste load of several hydrochloride salts in one serving.

Label-claim arithmetic

First decide whether the label declares L-lysine hydrochloride or L-lysine.

• Declaring the salt: divide the label claim by the assay fraction on the certificate of analysis.
• Declaring L-lysine: multiply the salt mass by the molar mass of L-lysine divided by 182.65 g/mol. Then correct for the assay.

Add any overage for shelf-life losses on top; the overage calculator does the arithmetic. Formats with reducing sugars may need a larger overage because of Maillard losses.