New protein ingredients for skin detergency: native wheat protein-surfactant complexes

Synopsis The cutaneous tolerability of detergent formulations can be improved by means of suitable additives. Exogenous proteins, for example, are able to reduce the skin irritation potential of surfactants according to a double mechanism: they complex the surfactant molecules lowering the concentration of their free monomeric species; they link to the skin keratin forming a protective colloidal layer that shields the denaturing attack of surfactants. Protein derivatives used as additives for detergency are usually prepared by partial hydrolysis of animal scleroproteins or plant reserve proteins. The main purpose of the hydrolytic cleavage is to make them water soluble and suitable for liquid products. Native, non hydrolysed wheat proteins have been recently introduced as active ingredients for detergents. Water solubility and stability are obtained by means of complexation with surfactants which also increases their actual hydrophobicity, an important parameter affecting cosmetic properties of proteins. The anti-irritant properties of these new derivatives of detergents have been evaluated by in vitro predictive tests (swelling response of collagen membranes), by acute irritancy in vivo methods (occlusive patch tests) and by use tests (forearm washing test). Transepidermal water loss and electric capacitance have been adopted as investigation techniques to evaluate the skin integrity/damage after the in vivo tests. The performance of native wheat protein-surfactant complexes has been compared with traditional protein hydrolysates and to amphoteric surfactants as detergent additives. The results show a noticeable reduction of skin irritation in surfactant formulations with addition of native wheat proteins.