Why marine collagen only up to 60 °C: an explanation from collagen chemistry

Marine collagen denatures at a lower temperature than beef collagen, because it contains fewer of the amino acids that hold its triple helix together. Fish collagen from cold-water fish starts to unwind at around 40 °C, whereas beef collagen holds up to roughly 65 °C. The up-to-60 °C rule gives marine collagen a safe margin and protects its structure during ordinary drink preparation. Boiling water at around 100 °C is above this limit.

Collagen is a triple helix, three intertwined strands. Their stability is held above all by two imino acids, proline and hydroxyproline. Their ring structures act as braces that keep the helix from loosening. The more of them collagen contains, the higher the temperature it withstands before it unwinds.

The unwinding of the triple helix is denaturation. Denatured collagen is neither destroyed nor toxic; it simply loses its original structure. In manufacturing, after all, collagen is deliberately and controllably cleaved, which is the essence of a hydrolysate. But in home preparation you do not want to damage the structure randomly with heat.

A classic analysis of fish collagens (Piez and Gross, Journal of Biological Chemistry, 1960) measured the composition of carp, cod and pike collagen and compared them with beef. Fish collagen has fewer imino acids (proline and hydroxyproline) than mammalian collagen.

Cod skin collagen had one of the lowest hydroxyproline contents, around 53 residues per 1000, and this corresponded to the low temperature at which it sets, around 40 °C. Beef collagen, with a higher imino acid content, denatures only at around 65 °C. Fewer braces therefore mean lower temperature resistance. That is the whole reason marine collagen requires gentler handling.

• Up to 60 °C, no more. Lukewarm to warm water, lukewarm tea, a smoothie, yogurt, water from the fridge. All below the limit.
• Never boiling water. Freshly boiled water is around 100 °C, far above the denaturation temperature of fish collagen.
• No coffee. Hot coffee is above 60 °C; on top of that, acidity and temperature together do not suit collagen.
• How to tell 60 °C. It is a temperature you can still comfortably hold on your lip, but it is not boiling. If you have a thermometer, you can be sure.

Sometimes a figure of around 140 to 150 °C comes up in connection with collagen. That concerns industrial sterilization during manufacturing, not preparing a drink at home. For your kitchen the simple limit holds: up to 60 °C.

Sources

• Piez K. A., Gross J. The amino acid composition of some fish collagens: the relation between composition and structure. Journal of Biological Chemistry, 1960. doi.org/10.1016/S0021-9258(18)69466-9