Washed yeast made my beer fruity!

[Poobah58]

Learned a valuable lesson. I recently made an Irish Red. Used the same recipe as I did back in January. It was good but a bit fruity. This was rather puzzling until I just tapped a Belgian Tripel I brewed in August. It's OK but it's fruity! I went back and looked at both recipes and they had a common denominator... I used some washed yeast. I brewed the Red in August and used some fresh yeast and some washed yeast from earlier in the year. I brewed the Tripel in August and used some fresh yeast and some washed yeast from last year. In June, I removed the washed Irish yeast, decanted and ranched up again. I did the same to the Tripel yeast in March and June. I do not recall if I added water after ranching back up. Don't know if it makes a difference or not. Anyway, If I reuse a yeast cake again it will be no older than 1 month!!!

 

[WoodlandBrew]

Sounds like the viability was lower than you expected. Did you make a starter from the washed yeast? There are too many variables in slurry cell counts to make estimating them feasible.

See this for details:
http://woodlandbrew.blogspot.com/2012/11/counting-cells.html

 

[Poobah58]

I'm sure yeast count was not a problem. Made starters from washed and fresh yeast.

 

[WoodlandBrew]

So what do you think was the problem? Are you suggesting that a starter made with old yeast, even at high viability, results in fruity flavors?

I've pitched 2 month old slurries and tasted no fruity flavors.

I guess if you made a 1 litter starter with a cup of a slurry you could be inoculating over 350 billion cells which would really limit your growth, and you would then be pitching mostly old cells. But even then there would be significant cell division in the wort when it was pitched.

What size starter, and how much slurry did you use?

 

[BBL_Brewer]

Did you use temp control?

 

[Poobah58]

Did you use temp control?

Yep.

 

[Poobah58]

So what do you think was the problem? Are you suggesting that a starter made with old yeast, even at high viability, results in fruity flavors?

I've pitched 2 month old slurries and tasted no fruity flavors.

I guess if you made a 1 litter starter with a cup of a slurry you could be inoculating over 350 billion cells which would really limit your growth, and you would then be pitching mostly old cells. But even then there would be significant cell division in the wort when it was pitched.

What size starter, and how much slurry did you use?

I've used 1-2 month old washed yeasts before with good luck. These may have gone beyond their limits. I gotta think the esters came from the washed (old) yeast. I've used these yeasts before in the same beers, pitched at the same rate and fermented at the same temps. My guess the old yeast was just a bit tired. I wonder if keeping them at fridge temps for so long makes the viable ones throw off these fruity esters? It is possible after I woke them up in the summer that I did not add water for storage. I just don't recall...

 

[BBL_Brewer]

Perhaps you should step your starters up a couple three times to make sure that you have plenty of healthy yeast before you pitch. You could up the pitching rate and see if that helps as well. I brew with frozen yeast, which can't be that different than using washed yeast. In both cases the yeast experience quite a bit of stress. I can't tell the difference between frozen yeast and a fresh smack pack. The yeast we get from the lab has been around for a very long time. They just grow up a bunch of it, package it and ship it out. Reusing yeast at home is no different. If you have been brewing with it for too many generations it can mutate, but if you're only reusing it a few times you shouldn't have any problems.