Learned from repitching on yeast cake and autolysis

[teutonic terror]

A few weeks back I made an APA and pitched it onto a yeast cake from another brew.

This weekend I racked it to a secondary to free up my 6.5 gal Ale Pail. I also washed the
yeast from said yeast cake.
Needless to say, it has to be one of the foulest smelling, and pretty bad tasting brews I've ever done!

I searched the Net to figure out what I was up against and found this .

http://www.brewboard.com/index.php?showtopic=114620

It describes exactly the smell and flavor of burnt rubber I've experienced in the past!

I'm done pitching on yeast cakes!

Now, I have to toss the three jars of yeast I harvested from that batch.
It wasn't futile, but great practice for the next time I wash yeast!

Glad I got an answer!

[mashani]

I've personally never had this happen in a small batch fermenter, I've re-used yeast cakes up to 3x, and gone 2-3 weeks each iteration. Its usually only a problem in a tall/narrow fermenter where lots of pressure gets put on the yeast cake.

[teutonic terror]

I've posted in the past about having a burnt rubber flavor and smell in a couple of brews.

That was the first definitive description of what I have experienced.
What is baffling me more than anything, I've had it happen using re-hydrated dry yeast as well as
pitching onto an existing cake.
But, I have also had great success pitching onto an existing cake.
Strange!

Now, could I be under pitching and stressing the yeast?
I don't do a starter and I rehydrate in about 2 cups of water.
Most of my beers are in the 1.045-1.060 range, so the are not really big beers.

Heat is pretty much a non issue because the room I use in the basement is quite cool and has little or no temperature
variation.
Also, the fermenter is a 6.5 gallon Ale Pail.

[mashani]

If you rehydrate a bit too hot you could kill off lots of yeast.

But I would not think this would give you the rubber/autolysis type flavors. An underpitched wort will grow as many daughter cells as is necessary to ferment or at least as many cells as can grow up to the nutrient levels and oxygen found in the wort. An under pitch can actually ferment out to a lower FG then a proper pitch *if* there are enough nutrients and enough oxygen. It can go just as low as a large over pitch. But it won't be as clean as a proper pitch rate.

The extended growth phase will make more yeast flavors, but they should not be of the autolysis variety, but simply more phenols or esters. It could allow other bugs to get involved in the fermentation up to a certain point - most bugs besides the yeast will die once you hit 2% abv and/or a proper PH. So if it takes a while for the yeast to do this, you can get "other bug flavor".

[teutonic terror]

Thanks mashani!

Alot of what you stated makes sense and I have noticed some of my FG's coming in low.
Not extremely low but lower than estimated.
I mentioned it to the LHBS head brewer and he told me it was a sign of healthy yeast.
Sounds like it could be both ways though.

I'll take what you have provided and do some more studying and research on the subject.
Always something else to learn!

[BigPapaG]

If I might add another question... Is it possible that you are tasting phenols that are band-aid-like?

There are a number of possible sources ranging from chlorophenols from highly clorinated water or water treated with chloramine, to rogue spoilage bacteria from algea present in surface water (prevelant during warmer months), to bacteria hiding in transfer hoses and plastic fermenting equipment etc.

It may not be what you are experiencing, but I don't think autolysis is the problem, I have to agree with mashani on that one...

So, ruling that out, it must be somethong else...

Some interesting notes on phenolic off flavors:

http://www.winning-homebrew.com/phenolic-flavors.html