Proteins are organic compounds present in both animal and vegetal organisms and are composed of long chains of amino acids linked together by amide bonds, called peptide bonds, that form between the amine and carboxyl group of the amino acids with the release of a molecule of water.

Amino acids differ from each other in the presence of a specific side chain that can have a nonpolar, polar, acid or basic nature and gives every single amino acids particular chemical properties.

Proteins differ from each other in the different presence, frequency and sequence in which the various amino acids can link together; the side chains can form bonds with each other making the polypeptide chain assume a particular spatial conformation or can associate with other side chains of another polypeptide chain. The spatial conformation of protein amino acid chains and the respective hydrolysates in general depends on the physicochemical conditions of the aqueous solution in which they are (pH, presence of ions, temperature, concentration, presence of certain organic compounds) and a variation of the equilibrium conditions can easily denature them (e.g. loss of solubility).

Proteins solubility is mainly affected by the molecular weight: at the same physicochemical conditions generally the decrease of the molecular weight causes an increase of protein solubility.

For native proteins we mean proteins isolated from vegetal or animal sources that maintain their original molecular weight and the amino acids chemical characteristics.

Hydrolyzed proteins derive from native proteins and are composed of peptides with a lower molecular weight but a higher solubility.

The hydrolysis of proteins can be carried out by adding strong basic or acid substances or via enzymatic means; chemical hydrolysis can be mild or strong and causes destruction of the amino acids chains, denaturation of some amino acids side chains and destruction of some amino acids. Enzymatic hydrolysis makes use of specific proteases capable of breaking up the amino acid chains in specific sites; this kind of hydrolysis doesn’t cause amino acids side chains denaturation and amino acids destruction.

Therefore we can refer to a protein hydrolysate ONLY as amino acids chains with different molecular weight that can be in aqueous solution or in a powder form; on the market there may be found substances formed by molecules of proteinic origin condensed with other molecules such as cationic compounds or fatty acids. This kind of substances are obtained through synthesis processes and form molecules with totally different properties than the ones of the proteins from which they originate.

During detergency the outermost layer of the skin comes in contact with surfactant substances capable of removing dirty but also part of the natural hydrolipidic component of the stratum corneum, causing a partial denaturation and depauperation of lipidic and proteinic substances with alteration of the normal cutaneus equilibrium; this can lead to an impairment of the skin barrier function with consequences that can range from stratum corneum hydration decrease to dermatitis in sensitive skins.

The use of proteins combined with tensides has proven to be an effective protection against the aggressive action of these substances without compromising their cleansing and foaming efficacy; the protection is carried out both through the formation of interactions between peptides and tenside monomers, that are those mostly capable of penetrating cutaneous membranes, and through the formations of weak but numerous bonds with the epidermic proteins which get covered by a colloidal protective film.

Proteins applied on skin form weak but numerous bonds with epidermic proteins creating a non-occlusive thin colloidal protective film: the higher the peptides molecular weight is the higher is the film-forming effect on skin; lower molecular weight hydrolysates, rich in small peptides and free amino acids, can have a buffering and humectant effect and be useful in products for skins that present deficient conditions in these compounds.

Some proteins exhibit an antiradical activity and can help to preserve other cutaneous components integrity (for example after UV exposure).