On a commercial scale, brewing is sometimes called “yeast farming”. Commercial brewers are continually monitoring their yeast, brewing batches to keep their yeast samples viable, and refresh their yeast bank. On a homebrew scale it is easy enough to buy new yeast, but it is possible to manage your inventory to save that expense. That was the genesis of this brew.
The 1272 American Ale II yeast in my yeast bank was harvested last March. At best ten percent of the cells in the jar are viable. I loved what the yeast contributed to Camp Randall Red IPA and the Blueberry Wheat kit that I brewed. I want to re-brew Camp Randall Red and potentially use 1272 in another batch, but it will take some work to step up the number of yeast cells to even brew a two or three gallon batch.
A stir plate spins liquid via a spinning magnet, which causes another magnet inside of the flask called a stir bar to also spin, causing the liquid in the flask to stir. The stir bar is roughly the size of a pill. They are small and very easy to lose. I have managed to lose three of them already. The next time I buy ingredients I will buy a new one and a backup, but in the meantime I have to do without.
The continuous stirring aerates the wort causing the yeast cells to multiply much more rapidly than they would otherwise. What that means is that I have to make a larger volume yeast starter to end up with the same number of yeast cells. The older yeast is, the less viable that it is. A six month-old package of yeast that originally contained 100 billion cells will only have a fraction of that number of cells. A best practice is to use yeasts every few months. That way you can continuously harvest new, healthy cells.
If I would need to eventually step up to a huge yeast starter as opposed to my usual 1200-2000 ml, I may was well brew a one gallon batch of beer. From there I designed a light, low gravity, low alcohol, and lightly hopped recipe that would not stress the yeast I plan to harvest from the beer. I started putting together an English Bitter (English Pale Ale) recipe that utilized leftover ingredients from previous batches.
Most of the ingredients are American. American Ale Yeast II shares some attributes with English yeasts. The only English ingredients are the hops. This won’t be a perfect example of the style. It may end up tasting more like a very low alcohol American Pale Ale.
To have enough cells to properly ferment this low volume, low alcohol batch, I had to make a small yeast starter just for this batch. After being dormant for so long, it took the yeast longer than usual to start fermenting the starter wort and multiplying. My starting gravity was a little low, so I added one ounce of corn sugar to compensate. The beer should still finish under 4.0 % alcohol-by-volume.
This beer is similar in strenguld use to make a yeast starter. The hopping is hopefully low enough as to not stress the yeast. Active fermentation was visible after only a few hours. After just a week I will bottle the beer and harvest the yeast. I will then pitch that yeast into another yeast starter to brew the next batch of Camp Randall Red IPA, and have fresh cells leftover to replenish my yeast bank.
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