[mugwort]

From "Take Two: Reusing Homebrew Yeast", page 58, BYO Sept '13

"Some homebrewers will reuse the yeast cake in its entirety, transferring a fresh batch of wort directly on top, into the old fermenter.  This is a terrible idea and is contrary to everything we know about proper sanitation procedures.  They will argue that they have never had an issue with this method.  My response:  If you haven't had an issue yet, it's just a matter of time."


Anyone else read the article and find the above a little odd?  I'd like to know why this is such a bad idea but can find no direct answers upon rereading the article.

I understand there are some good reasons to choose not to rack wort onto the cake of a just-finished fermenter.  Such reasons tend to mirror those pertaining to reusing yeast in any circumstance--if it has undergone excess stress, is mixed with too much trub or hops, is too old, is infected or suspected of, etc.

As for sanitation issues inherent in the reuse of a fermenter and cake, I fear I'm at a loss.

[philm63]

Just read that article this morning and I too was taken aback. I always thought if conditions were ideal and the yeast was healthy, and there was not too much hop matter, and the beer styles were similar or identical, pitching on the cake was OK.

Sanitation was likely one of the first things brewers learned and by the time one gets to the point they're ready to reuse yeast, they're likely pretty darn good with sanitation so I'm not sure where that's coming from.

[Slowbrew]

When I read that my thought was "statement of generalized personal opinion".  There are times when it is just fine to reuse a yeast cake and times when it is not.  Too much trub and hop junk would make it undesirable.  But a nice "clean" yeast cake no problem.

Paul

[kylekohlmorgen]

I don't think pitching directly on top of a yeast cake is as much a sanitation issue as it is an issue for yeast health and flavor contribution.

If you pitch on top of an entire yeast cake, in most all cases you are over-pitching by a significant amount. Over-pitching at this level will cause yeast derived off-flavors.

Pitching onto a yeast cake also carries over dead yeast cells which can autolyze and contribute a beef broth flavor to the beer.

IME the best way to reuse yeast is to harvest from the fermentor, clean/sanitize the fermentor, 'wash' the yeast with water, and repitch the correct amount of healthy yeast slurry, leaving the dead yeast/trub behind. Procedures for washing yeast can be found online; proper slurry pitch rates can be determined from Mrmalty Yeast Calculator (JZ's site).

The Yeast book is a great reference for demystifying all yeast handling practices.

[punatic]

"My response:  If you haven't had an issue yet, it's just a matter of time."

Well, the time frame being referenced must be longer than 24 years.  I've been doing it since 1989 and have not had an infected batch as a result... yet.  Thank goodness I've been informed of the eventual outcome of my unsanitary ways!  Here I was floating along in blissful ignorance.  Oh the humanity!

I don't do it every time, but I have done it pretty regularly.  Like Slowbrew-Paul says, there is nothing wrong with racking onto a clean fresh yeast cake.

I call it hot racking.  In the Submarine Service it means something a bit different, but the idea is the same and that's where I got the name for the process from.

[dmtaylor]

It is a terrible idea if the writer is a mass manufacturer of yeast and he wants to make money!  But otherwise, no.

[klickitat jim]

Meh,
I guess it's a good example that it's best to point out the strengths of your way of doing things rather than the weakness of the other way. In fact, pointing out the problems with other's methods is terrible and if it hasn't caused you problems yet, it will eventually

[reverseapachemaster]

More garbage homebrewing myth without any facts or common sense to back it up.

There are reasons not to pitch on the entire cake but sanitation is not one of them, unless you are unsanitary in your bottling technique and you are infecting your beer (and the cake) with the racking cane. Otherwise, I'm not sure how you are introducing a high probability of infection in the next batch. I guess opening the fermentor to rack out creates an opportunity for wild yeast and bacteria to fall in but not substantially different than taking a few extra minutes to transfer chilled wort into a clean fermentor.

I guess the argument can be made that some amount of wild yeast and/or bacteria inevitably get into your wort and will have an opportunity to reproduce with each reuse but it's not like batch two on the cake is going to become an infected mess. If that was true all the commercial breweries that repitch yeast would have many infected batches, in addition to all us homebrewers who repitch yeast from batch to batch.

[corkybstewart]

I brewed 3 consecutive beers without opening my conical: a low OG pale ale, a rye pale and eventually a porter, total time for the 3 beers was a little over 2 months.  On the lid around the opening for the therrmowell I found a quarter sized spot of mold, but it never got into the beer and all three beers turned out just great..  In fact I'm brewing a 1.050 pale ale right now to develop a yeast cake for a porter and then an imperial stout.

[Jimmy K]

"contrary to everything we know about proper sanitation" - As said, there are some reasons not to do this depending on circumstances, but the author is focusing on sanitation as the problem. I really don't know why pitching onto an old yeast cake would be less sanitary than any other yeast re-use method. The only exception might be if you acid wash the yeast to kill bacteria, but that's pretty advance and most people don't do it. Otherwise, contamination in the cake will carry through into the washed yeast. If you're bad with sanitation, extra yeast handling steps might even introduce new contamination.

[Joe Sr.]

Hooey.

If you have a sanitation problem it didn't come from reusing a yeast cake in this manner.  Sounds like a confusion of correlation and cause.

[mugwort]

If you pitch on top of an entire yeast cake, in most all cases you are over-pitching by a significant amount. Over-pitching at this level will cause yeast derived off-flavors.

Pitching onto a yeast cake also carries over dead yeast cells which can autolyze and contribute a beef broth flavor to the beer.

I sometimes wonder how much risk there is of overpitching on say, a month-old cake.  As the viability of the cake drops over time, does a long primary result in a cake suitable to ferment a comparable gravity wort without too big a yeast cell count?  Is there some decent window of time between overpitch and autolysis for those of us who want to keep the same fermenter rolling for another batch?

As long as we're shy of mass yeast death, I'd like to think there's a rack-onto-cake sweet spot.  A young primary cake of two weeks might be perfect for a higher-gravity wort, but all other things accounted for, the older the yeast cake the lower the OG wort the cake can support.

Hmmm.  What the fermenter-cake pitch has going for it is ease and simplicity.  I don't want to make it too complicated for myself.

[punatic]

I am not a pedantic brewer.  I repeat my sucesses and avoid my repeating my mistakes.  Minutiae are for the small-minded.

[jeffy]

I am not a pedantic brewer.  I repeat my sucesses and avoid my repeating my mistakes.  Minutiae are for the small-minded.

I always thought that minutiae were for the engineers.

[hopfenundmalz]

I am not a pedantic brewer.  I repeat my sucesses and avoid my repeating my mistakes.  Minutiae are for the small-minded.

I always thought that minutiae were for the engineers.

Add scientists to that, but as an engineer I must agree.