Originally Posted by biochemedic
Like they can be mutated/damaged and possibly produce off flavors...
I recall reading that above 7% ABV the yeast can start to get funky. If you're interested in starting to wash/save some yeast, there was a recent thread about taking part of your starter and just banking that to make your next starter from; ie, harvesting fresh yeast directly from your starter before pitching. Saves the trouble of washing, and you essentially have a new tube of yeast to make another starter from. For the life of me, I can't find the thread to link it, perhaps someone else's google shui is working better than mine tonight...
This is what I do. I purchased a dozen preforms (the tubes that White labs sells their yeast in) and when I'm ready to harvest I do a starter as usual on my stir plate, cold crash, decant, and fill 3 preforms plus the original white labs tube. Then I refrigerate the tubes in a vertical position, and feed the starter. Cold crash, decant, and then decant the 4 tubes. Top off with fresh slurry and pitch the rest to my beer. the original white labs tube is the last one I use, so I don't forget to re harvest. This way I avoid the taste of a dark beer in a lighter brew, and esentially am using yeast cells that have never seen anything but light DME starter wort. No washing required, and I can see from both top and bottomof te preform exactly how health the cells are. I have noticed that the top cells ( those exposed to the starter beer) tend to turn brown first. I suppose if I wanted to get a LOT of slurrey I could cold crash longer and decant to a thicker slurrey, but I have not yet had a batch that failed to produce a viable starter. This weekend I pitch a tube of scottish ale yeast that I had stored for 5 months. I believe this process is only effective if you use a stir plate. I think if I was doing intermittent shaking I wold probably go for the larger initial sample. Also, If i was ever in a position of having ALL my samples ort a particular yeast that were really old, I could toss them allinto a stater and do a restart just to harvest.