Winemaking by-products as a sustainable source of antioxidant and functional compounds

¹ Department of Pharmacological and Biomolecular Sciences, Universitàdegli Studi di Milano, via Balzaretti 9, 20133 Milan, Italy
² Consiglio per la Ricerca e Sperimentazione in Agricoltura – Centro di Ricerca per l’Enologia, via Micca 35, 14100 Asti, Italy
³ CRC “Innovation for well-being and environment, Università degliStudi di Milano, via Festa del Perdono 7, 20122 Milano, Italy

Abstract

In the last years, the international guidelines encourage the reduction of food waste or processing by-products to promote a circular economy approach. Winemaking represents one of the sectors with the highest by-products generation, with several potential negative impact on the environment. Winemaking by-products are mainly used to produce distillates or fertilizers, but the interest in grape pomaceas a potential source of phenolic compounds has considerably increased. The aim of this study was the application of in vitro methods for the characterization of the phenolic fraction of winemaking by-products from different red grape varieties, and, in parallel, the evaluation of their antioxidant activity. The methods were: 1) Folin-Cocalteau's assay for the quantification of total polyphenol content; 2) the vanillin assay for the assessment of total flavan-3-ols (proanthocyanidins) content; 3) the pH differential method for the quantification of total anthocyanin content; 4) DPPH assay for the measurement of total antioxidant activity; 5) High Performance Thin Layer Chromatography for separation of phenolic substances and assessment of their antioxidant activity. Although a significant differences among varieties, grape pomace, particularly when containing seeds, are generally a good source of polyphenols with a significant antioxidant activity supporting itsuse in formulating healthy products.