Definition - What does Grape Seeds mean?
Seeds are found in wine grapes and are also part of the pomace, which is a solid waste product from making wine. In winemaking, it is believed that the seeds can create a bitter wine, as they contain astringent tannin structure, which can be harsh on the palate in the final wine.
Some wineries try to remove excess seeds, however, it is a difficult process and it is often not practiced.
WineFrog explains Grape Seeds
It was once believed that having excess seeds in the grape must prior to starting fermentation, had some downsides. While the seeds can be removed using a special device, some wineries found the machine inefficient and costly. The seeds themselves contain high levels of astringent tannin, which in excess, were believed to make unpalatable wine.
However, in recent studies, seed tannin is proved to be no less tannic than the type found in grape skin. It has also been studied that the tannin polymer chains, which are created by skin tannin, are much longer than those created by seed tannin. On the palate, these tannic structures are bound with a protein in the saliva, which leaves you with scratching tissue without lubrication.
It is the tannin polymers which have longer chains that are more astringent than those with shorter chains. Therefore, excess unpleasant tannin originally believed to be caused by seeds has been debunked.