So there is a wide range of opinions how long yeast can keep. Some people claim that washed yeast shouldn't be used past 3 months, others feel that it can keep up to and past a year. My question is if I were to wash my yeast from the batch I have fermenting now is that yeast considered "new" yeast or is it two weeks old or however long I fermented? Does the time you can save yeast reset each time you ferment and wash?
Washed yeast considered 1st. 2nd. 3rd. 4th. 5th generation. keeping on your fridge doesn't count (up to your personal limit). Each generation mean less healthy yeast, cause by new fermentation and new washing. Each fermentation involve more dead yeast and less healthy cells. The washing it self contribute contamination too. To sum up, You can call it Yeast recycling rather then Yeast Washing. just because the yeast doesn't get washed.
What? I don't have the time to write a full response right now, but this is mostly incorrect. If what you are saying is true then we wouldn't be able to propagate yeast.
I'm not a yeast washer, but logically I think it would make sense to reset your clock at the end of active fermentation, i.e. the last time your new population actively fed. This is roughly the point they'll begin declining. But I think the important question is once the clock is reset, how long does the yeast remain viable? You asked about three months or a year. In both cases, you'll have some viable cells, but much different numbers of them. You might look to the Mr. Malty viability percentages as a starting point.
Mr malty is great as vike man mentioned... I have 1056 in the fridge right now that I washed out of the primary on 9/4/12.... Mr malty app tells me that yeast is at approximately 51 % viability and that my next recipe that is gonna be in the neighborhood of OG 1.068 will need about 200 ml of yeast cake which I just approximate from my 100 ml increment mason jars. Most people say mr malty errs on the side of more yeast rather than less but I like that
