Characterization of grape marcs from native and foreign white varieties grown in northwestern Spain by their polyphenolic composition and antioxidant activity

Antioxidant White Grape Seed Phenolics: Pressurized Liquid Extracts from Different Varieties

“…Treixadura seeds show the highest concentration of epicatechin of about 2–5 times the other grape varieties. Epicatechin-gallate ranges from 322 to 613 µg/g (dw) with a mean value of 431 µg/g (dw), and Godello seeds with the highest content; this is in accordance with the authors previous findings on Godello grape marc [ 7 ]. Regarding procyanidins, PB1 was in general at higher concentration than PB2, with the exception of Treixadura and Torrontés grape seeds.…”

“…This last variety contains much lower PB1 than the rest of the samples, 709 µg/g (dw), and also one of the lowest PB2 content. This low procyanidin content of Torrontés seeds was also found in this variety grape marcs [ 7 ].…”

“…It seemed then interesting to compare the polyphenolic content of seeds with that of the same varieties marcs. In this way, data from a previous work on the characterization of Galician grape marcs can be used for the comparison, taking into account that those data refer to a different vintage period (years 2010–2012) [ 7 ]. TP values for GSEs are about 3–4 times greater than TP content of marcs.…”

“…A comparison between grape marcs and seeds for these varieties can be made based on previous data [ 7 ]. An average of 4566 µg/g·dw was obtained for the sum of the individual concentrations in marc samples, so seeds contain about 5–9-fold higher polyphenols than marc.…”

“…During red winemaking, skins and seeds are in contact with the fermenting broth for several days, conferring red wine with a high concentration of polyphenols. However, in white winemaking, the grape juice ferments without the grape marc which, thus, maintains much of its polyphenol content [ 4 , 5 , 6 , 7 , 8 ]; but it is also a byproduct with a more complex composition, making it more difficult to separate the seeds. One interesting option to isolate white grape seeds is the bio-assisted separation that occurs during the vermicomposting of grape marc on an industrial scale, yielding not only a high-quality organic vermicompost that can be used as fertilizer, but also grape seeds, which becomes a ready-to-use source of bioactive polyphenols [ 8 , 9 ].…”