It has been known for many years that hydrolyzed proteins will make excellent additives for mildness in surfactant systems. A paper was published in the JAOCS, summarizing work done on the use of proteins as counter-irritants in surfactant systems. This showed that the most effective protein for functioning as a counter-irritant was a quaternized protein with an iso-ionic point of 10.
Hydroxypropyltrimonium Gelatin is a quaternized protein, which meets the above parameters. It is made by taking a high molecular weight Hydrolyzed Collagen (which is a heteropolymer with 20-40 monomeric units, i.e. each different amino acid is a “monomer”) and reacting it with a low molecular weight trimethylammonium chloride derivative.
This reaction can occur where there are side chain (epsilon) amino groups (lysine, arginine) and hydroxyl groups (serine, threonine) at the terminal amino group. Consequently, 4-5 of the trimethylammonium groups are covalently bonded to the polymeric chain.
Hydroxypropyltrimonium Gelatin is a light-colored, low-odor liquid product with an IP of 10. It is freely soluble in water and compatible with all forms of cosmetic formulations. It is a member of a class of extra-efficacy proteins that have been made truly cationic in nature, and show improved substantivity, enhanced moisture binding, and extra body-building abilities on the hair.
Cationic proteins form large polyanionic complexes with a popular mild primary surfactant, ammonium myristyl ether (3 moles) sulfate (ALES). These types of systems will have a lower critical micelle concentration and are less aggressive to the skin and hair. All this is achieved without reducing the cleansing properties of the composition.
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