Contribution of By-Products from Moldovan Red Wines to the Circular Economy: Physicochemical Analysis and Applications

The global wine industry generates substantial volumes of by-products, leading to significant environmental and economic challenges. This study explores the sustainable valorization of two key by-products from Moldovan red wine production—yeast lees and grape skin powder derived from autochthonous grape varieties Rară Neagră (RN) and Fetească Neagră (FN)—within the circular economy paradigm. Comprehensive physicochemical analyses demonstrated that yeast lees are a rich source of bioactive β-glucans (20.17–21.91%, w/w wet lees), proteins, and triglycerides; β-glucans of this type are reported in the literature to confer immunomodulatory and antioxidant properties, although these bioactivities were not directly evaluated in the present study. Grape skin powders exhibited high dietary fibre content and polyphenolic compounds, with FN showing superior total polyphenol content and antioxidant activity compared to RN. Advanced extraction techniques using green solvents such as glycerol, propylene glycol, and ethanol, including ultrasound-assisted methods, optimized polyphenol recovery while maintaining extract stability. Incorporation of these extracts into innovative oil-in-water cosmetic emulsions revealed notable physicochemical characteristics, with the RN extracts enhancing emulsion firmness via polyphenol–xanthan gum interactions, and the FN extracts providing high antioxidant potential without compromising texture. A preliminary single-subject biophysical assessment suggested good short-term skin compatibility, with hydration improvement and reduced transepidermal water loss in several formulations and no visible pigmentation; these observations require confirmation in a larger volunteer panel with dedicated safety testing. This work provides laboratory-scale evidence of the dual environmental and functional potential of recovering and applying Moldovan winery by-products, supporting their further development—pending pilot-scale and economic validation—as bio-ingredients for the food, cosmetic, and pharmaceutical sectors within a circular bioeconomy framework.