healthy starter from old yeast - dark layers in jar

[sowoah]

I was making a starter with another yeast for this weekends brew and I noticed my wlp090 was 4 months old, so I decided to make another small starter to "keep it going". The wlp090 was about 50-100b cells harvested from a starter. I noticed the beer had yeast bite when pouring it off. I assume autolysis. It was darker on the bottom of the cake and the top, but had some good looking yeast in the middle. The starter took off healthily after some hours and behaved as expected. After 36hrs I dumped it into a quart jar and crashed it.

The next morning I noticed it had formed 3-4 distinct layers of lighter(healthy) and darker color. It could be some trub from the wort, but I think it's mostly yeast considering how it settled in layers. Next to the jar for comparison is beautiful healthy white yeast, blowoff from my other starter. Is this dead yeast mixed with healthy new yeast? I'm wondering what the affects of this would be? Do the dead yeast cells eventually get consumed by living cells (like servomyces)? Do I need to worry about accumulation of dead cells as I continually propagate this culture of yeast?

Any insight into the color and the layering of the yeast in the jar is appreciated! The starter was 1.04, 1L, with an appropriate dosage of servomyces and on a stir plate.

 

[specharka]

You should be okay. Yeast autolysis is largely a homebrewer's old wives tale and doesn't really make a whole lot of sense when you get down to it. We simply do not stress our yeast like commercial breweries do. I've pitched and repitched generations of yeast, and have never come close to the symptoms of autolysis via fermentation. I am sure there are some dead yeast cells in that mason jar, but I don't think that they will have an impact on the finished beer.

Dead cells will accumulate, but if you're step-feeding and pitching the yeast along the way, the yeast quality will not depreciate. Just make sure you build starters from clean yeast instead of harvesting from fermenters and re-pitching. Makes for a much more consistent pitch, beer after beer.