Green and Quick Extraction of Stable Biophenol-Rich Red Extracts from Grape Processing Waste

The extraction of grape processing waste (wine pomace) via microwave hydrodiffusion and gravity (MHG) from three different cultivars grown in Sicily (Syrah, Perricone, and Nero d'Avola) rapidly affords aqueous extracts highly concentrated in valued biophenols including flavonoids, anthocyanins, and phenolic acids. The method does not employ organic solvent, acid, or base and does not require grinding or freeze-drying of the wine pomace nor separation of the grape skins from seeds and stem. All of the extracts have a pronounced stability, as shown by their red-violet color fully retained after storage for more than a year (15 months) in a freezer under air. Concentrations of phenolics up to 2000 ppm were detected in the aged extracts of Sicily's local cultivar Perricone, which also has the highest content of flavonoids. These findings provide a simple and economically viable extraction route to biophenol-rich red extracts that can be used as food colorants as well as to formulate nutraceutical, cosmetic, and personal care products starting from an agricultural byproduct available in >10 million tonne yearly amount.