Collagen peptides: source, molecular weight and the Bloom number that should not be there

Collagen peptides and gelatin are the same protein at different degrees of hydrolysis, and the specification that tells them apart is short. It is worth knowing which one is in the quote.

Gelatin or peptides

Gelatin gels. Collagen peptides do not — they are hydrolysed far enough that gelling capacity is gone, which is exactly why they dissolve cold and stay clear in a beverage. Bloom strength measures gel firmness, so a meaningful Bloom value on a peptide certificate is a contradiction: either the material is not fully hydrolysed, or the parameter has been copied across from a gelatin datasheet. Both are worth a question.

Average molecular weight

This is the defining parameter for peptides, typically 2,000 to 5,000 daltons for standard grades and lower for specialised ones. It drives solubility, viscosity in solution and mouthfeel. Specify the average with a range, and ask which method produced it — gel permeation chromatography is the usual answer, and results are not comparable across methods.

Source, and why it decides more than price

• Bovine hide or bone — the volume material. Bone-derived requires attention to the TSE/BSE risk statement and country of origin.
• Porcine skin — widely used, and disqualified outright for halal and kosher markets.
• Marine (fish skin and scale) — lower molecular weight typically, carries an allergen declaration, and is the usual choice where porcine and bovine are both unacceptable.
• Poultry — the usual source for type II collagen materials.

Source also determines the collagen type, and type is what the downstream marketing claim usually rests on. Type I and III come from skin and bone; type II from cartilage. A specification should name the type as well as the animal.

The rest of the specification

• Protein content, with the nitrogen conversion factor — 5.55 is conventional for collagen, not 6.25.
• Ash and moisture, plus solubility in cold water at your working concentration.
• Odour and clarity in solution — the practical failure point for beverage applications, and worth assessing on a sample rather than on paper.
• Heavy metals and microbiology, and for bovine material the full TSE statement with country of origin.
• Hydroxyproline content, the collagen-specific amino acid and the best confirmation that what you have is genuinely collagen.

Test the solution, not the powder

Every collagen peptide looks the same as a white powder. Dissolve the sample at the concentration and temperature your product uses, and judge it on clarity, odour and taste. That five-minute test rejects more unsuitable material than the certificate does.