Wednesday, August 17, 2011

Mysteries of Hydrolyzed Proteins

Updated: October 2017

I have been researching various proteins used in hair products. Claims that this or that protein are high or low molecular weight and therefore good for this or that fell short of an adequate explanation. And some people can use one type of protein, but not another. Some proteins are lauded as being good for certain hair concerns. Okay, why?

The weight of the protein does play a role, and it makes sense if you compare proteins. I converted all weights to the unit “Daltons.” Smaller numbers are easier to deal with, reducing them to Kilodaltons gave some numbers which seemed a bit misleading.

Hydrolyzed Protein Source
Weight in Daltons 
©Science-y Hair Blog 2017

Amino Acids
Less than 200 (usually)
Human hair keratin
Wheat (low molecular weight)
1000-10,000 (depends on the supplier)
1500 (approximately)
1000 (approximately)
1000 (approximately)
1000 (approximately)
1000 (approximately)
Sweet almond
3000 (approximately)
Gelatin (partially hydrolyzed collagen)
60,000 – 200,000 (from a variety of sources)
Each hydrolyzed protein may have amino acids and peptides in the solution as well (smaller molecules).
My sources are varied and so some are showing a range, including peptides (very small “protein” fragments) some show only an average. You can see that some proteins have a broader range of “protein sizes” which refers more to the methods used to identify the protein’s constituents and what I could find reported for that protein.

What is means for your hair: Low-weight hydrolyzed “proteins” are less than 1000 daltons. They’re not whole proteins anymore! Very small molecules (200 to 500 daltons) can penetrate the hair beyond the cuticle. Any and all of these proteins may contain smaller constituents that may penetrate. Penetrating into the hair can help improve elasticity of hair and moisturize deeply.

“Heavy” weights greater than 10,000 (or 80,000 depending on which source you consult) daltons are thought to be good film-formers for shine, body, helping fill in porosities in the cuticle. They are acting at the cuticle, forming a moisture-holding, protective coating and also having the potential to improve hair’s elasticity and strength. 

Medium weight protein hydrolysates (1000 to 5000 daltons) are substantive to hair (bond to hair, don’t rinse off readily). This helps reduce friction (tangling, difficulty combing) which ultimately reduces hair breakage. 

If you want a maximum protein boost, choose a mixture of proteins.

If your hair reacts badly to, say, hydrolyzed rice or quinoa protein but not to keratin, you may have your answer – the hydrolyzed rice or quinoa is forming a film on your hair, first and foremost whereas some of the keratin is also penetrating the deeper cuticle layers and possibly into the hair fiber.

Some hair will respond well to only certain proteins, or only in certain amounts. Light and medium weight proteins help keep hair hydrated by preserving water in and around the hair. Heavy-weight proteins help keep hair hydrated also by forming an invisible film (like a "glaze") over your hair.
There is a post here about the amino acid content of some proteins that further explains why some proteins may work better than others, but for a different reason.

Damaged (porous) hair may appreciate a broad range of proteins, amino acids and peptides to fill in the gaps of damaged cuticles, moisturize, and bond to the hair for ease of combing.

Proteins (top molecules) heated in an acid,
in the presence of water breaking into smaller "pieces"
thus a hydrolyzed protein.
Image from:
Proteins are used as humectants in cosmetics. But they're not humectants like glycerin or sorbitol or propylene glycol which are more "sugary" in nature. In fact - I think a food analogy is good here. If you put some wet brown sugar and some raw egg white on a plate and wait to see which evaporates first - the sugar dries faster. The proteins in the egg white do not release their water as easily. And as you may know - raw egg white dries to a very stiff film. I'm not advocating putting raw eggs in your hair. The proteins are too large to be useful. But you get the idea.

Hydrolyzed proteins in your hair products do the same thing - as humectants they attract and hold water and as protein-based humectants they lose that water slowly. Unlike glycerin or sorbitol or propylene glycol. Because water is what keeps hair hydrated and well-hydrated hair is strong and flexible, this is a wonderful benefit! Proteins or amino acids are ideal for silky or soft hair which is weighed down easily by oils and conditioners. Or for hair that snaps when you run your fingers through it.

There is a list of protein-containing shampoos and conditioners in the "Products By Category" page on this blog.