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Yeast wsahing... How long is too long?

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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!!!

I just started washing and reusing yeast.  I recently brewed a Hefeweizen with yeast that I had in the fridge for about 3 months.  I took one mason jar and made a starter.  It came out great and I couldn't tell a difference between the first batch w/ WY3068 and the second one with the washed 3068.  Same results with an Amber I did earlier in the year when I used washed WY1056 that was about 3 months old.  Again, I made a starter with that batch.  I've read posts on here and other places where brewers have had success with much older washed yeast product.

I made yeast starters for the washed and fresh yeast. Didn't combine until I knew that both had taken off. I'm sure cell count was not the issue.

interesting observation. Since you mixed yeasts its difficult to tell if the increased esters came from the fresh or old yeast.

I don't think old yeast slurries perform well and in your case, where a new and pure culture is available, I suggest propagating a full pitch from that. Even with old slurries I suggest propagating from a small sample if the purity of the yeast can be trusted.

There are lots of contradicting statements regarding ester creation by yeast. One thing that is common to all is that acetyl CoA, an intermediary compound that the yeast produces when it metabolizes sugar, becomes available for ester production. That can happen when the yest produces more than it can use for its growth. An "overflow" of this compound into ester production can be caused by many factors including yeast health, I think.


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.
BTW I used WY1338 for the Irish and WY1214 for the Tripel...


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