Estudo do armazenamento, das isotermas de adsorção e aplicação cosmética dos pós de Saccharomyces cerevisiae obtidos por secagem em camada de espuma

Abstract

The valorization of agro-industrial by-products represents a fundamental strategy for the development of more sustainable and economically viable production processes. The residual biomass of Saccharomyces cerevisiae, obtained after successive fermentation cycles in cachaça production, exhibits a composition rich in proteins, polysaccharides and minerals, features that make it a material with high biotechnological potential, despite still being commonly discarded by the industry. This study aimed to evaluate the technical feasibility, stability, and cosmetic potential of the powder obtained by foam-mat drying. Moisture adsorption isotherms were determined at 15, 30 and 45 °C, with the Henderson model providing the best fit to the experimental data, yielding type II sigmoidal curves. Thermodynamic analysis revealed that the isosteric heat of sorption (Qst) ranged from 44 to 50 kJ mol−1, indicating strong initial interactions between water molecules and active sites of the matrix. Differential variations in enthalpy (ΔH) and entropy (ΔS) decreased with increasing moisture content, evidencing greater organization of the adsorbed water layers and lower energy required for sorption. Negative Gibbs free energy (ΔG) values confirmed the spontaneity of the process and the affinity of the dried yeast for water. Among the drying conditions evaluated, the central point (60 °C and 10% foaming agent) showed the best performance, resulting in a more stable and less hygroscopic powder, which was selected for the subsequent stages of the study. During 90 days of storage in different packaging materials, under ambient (26 °C/75% RH) and accelerated (40 °C/75% RH) conditions, storage time was the most influential factor, followed by temperature and packaging type. Increased time and temperature intensified moisture gain and color variations, while high-density polyethylene (HDPE) packaging provided the best water-vapor barrier, preserving physicochemical properties for longer periods. Shelf life was estimated using kinetic modeling based on the Arrhenius equation, considering water activity and moisture content as critical parameters. The material packaged in HDPE and stored under ambient conditions showed the longest stability, with a shelf life of 12 months. In addition, the powder obtained under the central-point condition was incorporated into a cosmetic facial cream formulation, which exhibited a homogeneous appearance and no phase separation. Rheological analysis indicated pseudoplastic behavior well described by the Herschel–Bulkley model, demonstrating good structural stability. The presence of the active ingredient acted as a rheological modulator, reducing rigidity and improving flow, which resulted in greater spreadability and superior sensory performance compared with the control formulation. These results confirm that foam-mat drying is a viable and efficient technique for producing Saccharomyces cerevisiae powders with adequate stability and strong potential for application in sustainable cosmetic products.