Bagaço de malte: valorização do subproduto em aplicações cosméticas sustentáveis

Abstract

Brewers’ spent grain (BSG) is the main solid waste generated in the beer industry and contains phenolic compounds with antioxidant potential. As there is a growing demand for cosmetic formulations with natural and biodegradable ingredients, this study aimed to obtain and characterize BSG extract, in addition to developing and characterizing starch and poly(vinyl alcohol) films, starch nanoparticles, and a Pickering emulsion, to achieve sustainable cosmetic formulations. The extract was obtained through maceration and Soxhlet extraction, characterized by its total phenolic and flavonoid content, and evaluated for antioxidant and prebiotic activities, as well as cytotoxicity in fibroblasts. The films were developed using solvent casting and characterized by their mechanical, structural, and barrier properties, as well as the release of phenolic compounds. For the nanoparticles and Pickering emulsion, the mean diameter, polydispersity index (PDI), and zeta potential were evaluated using photon correlation spectroscopy, along with the encapsulation efficiency (EE) for the nanoparticles. The Pickering emulsion was stabilized by starch nanoparticles, and the safety was evaluated by the chorioallantoic membrane test (HET-CAM). The extracts composed of Pilsen and Rye BSG (EBMP and EBMC, respectively) were those that presented the highest values for total phenolic content, being 2.82 ± 0.03 and 4.28 ± 0.14 mg EAG.g-1 , respectively, and consequently, the most significant inhibition of ABTS radicals, with IC50 values of 240.10 ± 1.60 and 174.80 ± 4.90 µg.mL-1 , respectively. The flavonoid content was higher in the EBMP extract (1.00 ± 0.11 mg.g-1 extract) when compared to EBMC (0.11 ± 0.01 mg.g-1 extract). In addition to the antioxidant activity, the EBMP extract demonstrated prebiotic action for Lactobacillus acidophilus. In both cytotoxicity methods (MTT and neutral red), there was a reduction in cell viability of < 50% at a concentration ≥ 10 mg.mL-1 for EBMC and at a concentration ≥ 5 mg.mL-1 for EBMP. Increasing the extract concentration to 10% (%, w.w-1 ) in the films, when compared to the film with 5% (%, w.w-1 ) extract, significantly influenced the increase in apparent opacity (53.98 ± 6.73 %.µm-1 ), the reduction in water vapor permeability (1.41 x 10-11 g.m-1 .s-1 .Pa-1 ), the increase in tensile strength (14.71 ± 3.70 MPa) and elastic modulus (256.27 ± 99.97 MPa) and the reduction in elongation (7.05 ± 1.97%). In the release test in a pH 5.5 buffer medium, it was observed that all the extract was released during the 4-hour testing period in films with 5% and 10% (w.w-1 ) extract. The nanoparticles presented a diameter range between 181-200 nm, were considered monodisperse (PDI = 0.26-0.36), and the increase in the extract concentration to 10% (w.w-1 ) caused a reduction in the zeta potential (-12.00 ± 1.10 mV). The EE of 90.34% for nanoparticles with 5% (w.w-1 ) of extract and 6.67% for nanoparticles with 10% (w.w1 ) of extract demonstrated that the increase in extract concentration caused a reduction in the EE. No vascular signal was observed in the HET-CAM test in the tested emulsions. Both the films and the nanoparticles with a concentration of 5% (w.w-1 ) of the extract showed the most promise for application, considering mainly the mechanical aspects, permeability to water vapor, and encapsulation. Therefore, the results provide an experimental basis for evaluating the formulations as viable and safe strategies for the topical application of BSG extract, which exhibits antioxidant and prebiotic actions.