We started harvest about ten days ago so I wanted to talk about grapes today. Wine grapes have three parts: the skins, the pulp, and the seeds. The seeds have been bred out of table grapes, one example being Thompson seedless grapes.
Let’s start from the inside with the seeds. Seeds are not very tasty since they have very high amounts of tannins and do little when it comes to winemaking. If you have ever bought a bag of concord grapes and then bit down on the seeds you know how bitter the seeds can be. That being said, the last thing a winemaker wants to do is crush the seeds when the juice is pressed otherwise this bitterness will find its way into the juice. Grapes can have anywhere from one seed per berry up to four seeds per berry.
The most important part of the grape for white wine is the pulp. This contains the sugar, acids (both tartaric and malic), aromatics, and a small amount of potassium. A white wine gets all of its acid and flavor profile from the juice that is extracted from the pulp.
The last and most important part of the berry for a red wine is the skins. The skins contain all the color (called anthocyanins) in a red berry and thus need to be left in contact with the juice for the wine to have a red color. If the grapes are pressed shortly after they are crushed then the wine will be similar to a white wine or be rose in color. This part of the grape also contains the less bitter tannins that a winemaker wants in a red wine; it helps to give the final product a better mouthfeel.
-Brian Tomasello 4th Generation Outer Coastal Plain Winemaker Tomasello Winery
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