Changes in yeast

[tedandlea]

I have noticed an interesting alteration in the yeast I have been using lately. I bought a tube of White Labs California Ale Yeast WLP051 in November, '09, and have used it in making an amber ale. At the time of racking to the secondary, I save the top yeast in a quart or so of the fermenting beer, and refrigerate it up to a month until I made a new batch. Each generation was done in the same way until G6, when I noticed that very little top yeast was left, so I took a sample of the bottom yeast. For my last batch, which gave me G8 yeast, all the active yeast was at the bottom, none at all on top. I will bottle this batch tomorrow, then see how it tastes. However, all previous batches made from this starting yeast were excellent, even though it kind of seems like my yeast changed from an ale type to a lager type through 1 year of usage! Also, the yeast is now much more flocculent than it was when purchased.

By the way, all my beer is all-grain, primary fermenter is conical, secondary is a carboy.

 

[wonderbread23]

By selecting yeast from certain parts of the fermentor, you're putting selective pressure on the yeast, so over time the yeast will change to the properties you're selecting for. For example, if you tend to take from the top of the cake, over time the yeast will become less flocculent and more dusty. This selective pressure will not however change the species of the yeast (lager vs. ale). These are completely different creatures; one cannot transform into the other.