One of the things we deal with is purchasing yeast every time we create a wine, beer, mead or other alcoholic beverage. As far as “In Period” is concerned, this is a foreign concept. A brewer may have bought beer from another source and used the residual yeast in the bottom of the container to start a new batch.
Yeast was a location by location commodity because brewers were not aware of it’s existence beyond the brown scum left in the bottom that they poured into the next batch or thrown out.
If we’re to assume that yeast was poured from one batch to the next, eventually the quality degrades and the batches of beer or wine become sour. The safer route would be to allow a new batch of naturally occurring yeast to be introduced. This leaves a lot of lottery play in the beer creating process. The next yeast to innoculate the beverage could be stronger or weaker or induce off flavors. Consistency would be a miracle at best.
It wasn’t until later that the process of bacteria, virus and yeasts were starting to be understood by Louis Pasteur. Once recognized, yeast could be introduced to the next batch with far better regularity but it’s still important to come up with a clean batch of yeast for use.
Today, purchasing yeast is a no brainer. For about 1-2 dollars a batch of yeast can be purchased and used with little effort. However, if you want to get more than one use out of your yeast, it’s possible to condition it a few more times.
So we have moved the beer from the carboy and are left with the nasty sludge at the bottom of the container. Not all of this is useful. We want to seperate the yeast that’s still alive from the dead yeast and hulls. The dead yeast can be dried and sold as “Yeast Nutrient” but we’re not going to go there. We’re only interested in the live stuff.
First we want to take about 1 gallon of water and boil it to kill any bacteria. Once this is done we rapidly cool the water and then pour it into the carboy. By agitating the sludge together with the water, it breaks it free and we can get the live and dead yeasts suspended in the water.
After the water is mixed with the yeast you can lay the carboy on it’s side and give it 30 min. As you can see the carboy is open to the air. The water protects the yeast and the live yeast will continue to float while the dead stuff drops the bottom. After the 30 minutes are over, pour off the lighter colored liquid into a 1 gallon container.
Again we’ll leave the mixture alone. Usually for two hours the yeasts will seperate further and then you’ll pour the mixture off again into batch containers, leaving the smaller sludge behind.
At this point, the mixture can be put in the refrigerator and in a couple days the brown liquid will continue to clear so that all is left is a small amount of yeast at the bottom and a large amount of clear liquid. The yeast is viable for another two or three weeks in this format. When you go to use the yeast again, pour of most but not all of the water. Use the last little bit to raise the yeast off the bottom of the container to create your starter.
The starter begins as a simple sugar syrup equal parts granulated white sugar, poured into boiling water and rapidly cooled to about 70 degrees. Add the yeast to the mixture and within the time it takes to whole grain brew your next batch of beer or process your next wine, the yeast will be ready.