Pressing is an incredibly important part of the winemaking process and one which many consumers take for granted in the wines we drink. When the grapes get pressed will differ depending on the type of wine that is being made. Grapes going towards white wine will typically be pressed before fermentation, while grapes destined for red wines will be pressed after fermentation.
Most grapes, whether they are red or white-skinned, produce white juice. Yes, that means that Cabernet Sauvignon and Riesling will have the same coloured juice when being pressed. In order to make red wine red (or rosé in some cases), the juice must be kept in contact with the skins to help leech out the colour from the skins, which typically takes place over the fermentation period.
This is now where pressing the grapes becomes a true art, and is one of the biggest influences that a winemaker can have on the finished product. Free-run juice occurs when the juice is extracted from the weight of the grapes themselves. This is typically the highest quality juice to create the highest quality finished wines. The remaining grapes (must) will then be pressed. At Lakeview Wine Co. we use pneumatic bladder presses, which allows the winemakers to have the most control possible when it comes to pressing the grapes. The press has a rubber bladder that will be inflated with air to different pressures to gently squeeze some of the remaining juice out. This is called press-run juice. At this point, there is still juice remaining in the grapes, however, pressing further elevates the risk of breaking seeds, and pressing out undesirable compounds from the grapes, which would make their way into the finished wine, which is of course, not ideal.
While the remaining must still has some juice content inside, typically wineries will compost the must and spread it across the vineyard to act as fertilizer. Some wineries are sending the used grape skins to breweries to create wine-beer hybrids. Wineries are also able to make Piquette from the remaining must, which is a low ABV, wine beverage.
After being pressed in one way or another, the juice will be allowed to clarify and settle in the tank before undergoing the next process. Pressing has a large influence on the finished product and is an aspect of the wine product that most people have little knowledge of. Hopefully, this has been able to help everyone understand just a little more about what happens to the grapes before making it into the finished bottle!