Grape seeds represent a high percentage (20% to 26%) of the grape marc obtained as a byproduct from white winemaking and keep a vast proportion of grape polyphenols. In this study, seeds obtained from 11 monovarietal white grape marcs cultivated in Northwestern Spain have been analyzed in order to characterize their polyphenolic content and antioxidant activity. Seeds of native (Albariño, Caiño, Godello, Loureiro, Torrontés, and Treixadura) and non-native (Chardonnay, Gewurtzträminer, Pinot blanc, Pinot gris, and Riesling) grape varieties have been considered. Low weight phenolics have been extracted by means of pressurized liquid extraction (PLE) and further analyzed by LC-MS/MS. The results showed that PLE extracts, whatever the grape variety of origin, contained large amounts of polyphenols and high antioxidant activity. Differences in the varietal polyphenolic profiles were found, so a selective exploitation of seeds might be possible.

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Galicia region (Northwestern Spain) wine production is mainly focused to high-quality white wines. The polyphenolic composition and the antioxidant activity have been determined to characterize the wines obtained from white grape varieties (Albariño, Branco Lexitimo, Caiño blanco, Godello, Loureiro, Torrontes, and Treixadura) grown in Galician protected production areas, and the wines elaborated with non-native varieties experimentally grown in Galicia (Chardonnay, Gewürztraminer, Pinot blanc, Pinot gris, Riesling, and Sauvignon blanc). Since Albariños are the varietal wines with the highest production and commercialization extension, we have studied their polyphenolic composition as a function of the production subarea. Three vintage years (2010, 2011, and 2012) have been considered to account for climate variability. Liquid chromatography with diode array and mass spectrometry detection was used to obtain the phenolic profiles. Wines from native grapes could be fully discriminated by their phenolic composition, with only Albariño being partially confused with other varietal wines. Albariño wines produced in O Rosal and Ribera do Ulla could be clearly differentiated, whereas Condado do Tea and Val do Salnés wines were partially confused. The polyphenolic profile was enough to differentiate the wines obtained from non-native grapes. The total polyphenols content and the antioxidant activity of white wines elaborated in Galicia were comparable, although significant differences were found among varieties.