Last time we began looking at the wine making process, starting with the grapes. While the grapes certainly are the most important ingredient in wine making, there is another very important ingredient - yeast. So, let’s take a look at the fermentation process.
Once the grapes are harvested and prepared for the wine making process, it time to turn the grape juice to wine. Large tanks are used in this process and here is where yeast is added. It's the natural sugar in the juice of the grape that gets consumed by the live yeast. The bi-product of the yeast's consumption of sugar is alcohol and carbon dioxide (CO2). Remember that red wines have the juice and skins together in the fermentation tank and the production of CO2 causes all the skins to float to the top of the tank. So winemaker's have to periodically 'punch down' the skins to intermix them with the juice or 'pump over' the juice as another means of keeping the skins mixed in with the juice. But regardless of the grape type, the fermentation process is relative quick, lasting typically from ten days to two weeks. And, another factor limiting the fermentation time is the life of the yeast. Depending on the strain of yeast, the fermentation process will stop once the alcohol level reaches levels of 16-18% when the yeast dies or after all the sugar is consumed.
Once fermentation is complete, white wines will be transferred to stainless steel tanks or oak barrels for aging. Red wine will then be separated from the skins and moved to vessels for aging. And, that’s where we’ll pick up next time - aging of wine. Cheers!