From a By-Product to an Active Raw Material: the Use of Brewers’ Spent Grain Extract in Cosmetic Masks

Brewers’ spent grain (BSG) is the primary by-product of the brewing industry, being a source of phenolic compounds associated with antioxidant activity. In this study, starch/polyvinyl alcohol (PVA) films with BSG extract were developed as an alternative anti-aging and sustainable cosmetic mask. The influence of BSG extract (concentrations of 5% and 10%) on the structural, thermal, mechanical, and barrier properties of the starch/PVA films was evaluated and compared with the Control film (without BSG extract). The in vitro release of phenolic compounds from BSG extract incorporated in the films in water and skin simulant medium (pH 5.5) was also evaluated. By increasing the BSG extract concentration to 10%, the film matrix became more cohesive and homogeneous, as demonstrated by the FEG-SEM images, resulting in greater tensile strength when compared to the Control and 5% BSG extract films. The films with 10% BSG extract were more rigid (lower elastic modulus) and brittle (lower elongation at break). The yellow extract coloration increased the opacity of the film with 10% BSG extract and a reduction in water vapor permeability due to the lipophilic character of the extract. After 4 hours, all films evaluated showed a complete release of phenolic compounds from BSG extract, which indicates their active role as anti-aging cosmetics. Based on the results, films with 5% BSG extract present interesting characteristics to be a natural and eco-friendly alternative to facial beauty masks.