Scribbles & Bits from the Vines to the Wines and Beyond at PEJU
Wednesday, October 17, 2012
The Magic of Yeast
The heavenly smell of fermenting red wine now fills the winery, and we have the power of yeast to thank for that. Yeast plays an essential role in winemaking as it converts sugar into alcohol. Without it we would have nothing more than old grape juice.
However, jumpstarting the process is a bit more complicated than dumping some yeast into a tank, so I looked over some shoulders today as we gave the yeast some TLC before inoculating.
When preparing a yeast culture, first it is necessary for the yeasts to be combined with a high temperature liquid. The heat allows the yeast to disperse throughout the liquid and keeps the yeast cells stable.
From there, the yeasts must be slowly and carefully cooled down, so that they can be transferred to the grape must, which is typically kept at around 58 F. Inoculating when the must and yeasts are within about ten degrees of each other ensures the yeast makes a smooth transition and doesn't experience any "cold shock", which could negatively affect the fermenation process.
For the yeast required for just one tank, this temperature adjustment process takes an entire day. Then the yeast is finally introduced to the must, they get to work on eating those sugars, and we get to go home. Just one of hundreds of examples of how in winemaking, the little tasks and details create a final product that is far, far greater than the sum of its parts. :)