Verio

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Reposting this as a new thread, so I don't hijack the Yeast Cake thread.

Can someone explain the science to me on this? Why is a Yeast Cake viable after a beer has been sitting on it for potentially months, unrefrigerated, but as soon as the beer is mostly racked off of it, it's only viable for a few weeks, and must be refrigerated during that time?

cheezydemon3

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That science is horsesh!t in my book.

Seeing is believing for me.

Yeast hasn't been around for millenia bacause it is so fragile and sickly.

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MalFet

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I suspect the logic has more to do with sanitation and less to do with actual yeast population.

Yeast is pretty good at going dormant when food sources disappear, but it is still vulnerable to infection. I'm not so sure I'd assume that a yeast cake _months_ old would be a great source of healthy yeast, but whatever is there is likely going to be clean because it is sealed off from the environment by a layer of fermented beer. Yeast in a mason jar is more vulnerable to bacteria either left on the jar or introduced during transfer.

Verio

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Well, some people are touting around here like they're experts on yeast, so I'm quite intrigued on the matter.

How can an organism that requires refrigeration and supposedly an "ice pack" when shipped to my house, be viable after sitting for 2 months in my closet at 75 degrees unrefrigerated?

Does a magical transformation happen when I rack my beer off, that makes the yeast now need refrigeration to survive? If that's the case, why not leave an inch or two of beer on top, and then have my yeast viable for much longer unrefrigerated?

Revvy

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The beer protects the yeast from spoilage since it's an anerobic enviroment. Once it is exposed to air with pontential nasties it's gonna get contaminated. You put it into a sealed jar with more liquid over it (whether you clean it or not as long as you fill the airspce) or you slant it, cool it to dormancy temps, so it's not active and hopefully not mutating.

What's so hard to grasp about this? What am I missing here? What's the beef about that?

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Verio

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The going advice for the month on here is to let your beer sit for 2 months before bottling or kegging. That's the information being pasted into almost every newbie post by Revvy and others.

If yeast is protected from infection and stable after being dormant, what's the timetable on how long its viable? Does yeast decay over a certain amount of time, and if so, what's the timetable? Does refrigeration delay decay?

Verio

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My beef is that spending the extra time of scooping the yeast, washing it, and then having it potentially only viable for a few weeks in the fridge seems like a bad piece of advice.

Based upon your information here, I could just rack 95% of my beer off, leave my yeast cake to sit for however long I wanted in dormancy in the fermentor and then when I'm good and ready to make a new batch of beer, scoop the yeast, wash it, and then make good beer.

Dormancy of yeast would have nothing to do with an infection. Bacteria will grow whether or not the yeast is alive. That's why food still rots in a fridge.

Revvy

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Who the helll says it's only viable for a few weeks??????

If you made a starter, then the age of a yeast isn't really an issue.

Bobby M did a test on year old stored yeast here; http://www.homebrewtalk.com/f13/testing-limits-yeast-viability-126707/

And my LHBS cells outdated tubes and packs of yeast dirt cheap 2-3 dollars each and I usually grab a couple tubes of belgian or other interesting yeast when I am there and shove it in my fridge. and I have never had a problem with one of those tubes.

I usually make a starter but I once pitched a year old tube of Belgian High Gravity yeast directly into a 2.5 gallon batch of a Belgian Dark Strong, and after about 4 days it took off beautifully.

With any stored, old yeast you just need first to apply the "sniff test" if it smell bad, especially if it smells like week old gorilla poop in a diaper left on the side of the road in the heat of summer.

Then make a starter, and if it takes off you are fine. The purpose of a starter is to reproduce any viable cells in a batch of yeast....that;s how we can grow a starter form the dregs in a bottle of beer incrementally...and that beer may be months old.

Even if you have a few still living cells, you can grow them....That's how we can harvest a huge starter (incrementally) from the dregs in a bottle of some commercial beers. You take those few living cells and grow them into more.

If yeast can be grown from a tiny amount that has been encased in amber for 45 million years, 45 million year old yeast ferments amber ale we really don't need to sweat too much about how old a yeast is, if it's properly stored.

Really even with "old yeast" if there is a few cells, they will reproduce. In your case it may just take awhile.

I know other folks on here who have gone a couple years with harvested yeast.

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Revvy's one of the cool reverends. He has a Harley and a t-shirt that says on the back "If you can read this, the bitch was Raptured. - Madman

I gotta tell ya, just between us girls, that Revvy is HOT. Very tall, gorgeous grey hair and a terrific smile. He's very good looking in person, with a charismatic personality... he drives like a ****ing maniac! - YooperBrew

Revvy

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I dunno, if you managed to protect that 5% of beer once you racked off the rest of it from getting infected (like racking it to a gallon jug to reduce headspace, you probably would be fine.

Give it a try and report back.

Another thing that occured to me about yeast and yeast viability,.

I don't know if you know the story of Charlie Papazian's yeast (White Labs "Cry Havoc") or not. He talked about it on basic brewing. The recipes in both Papazian's books, The Complete Joy of Homebrewing and The Homebrewers Companion, were originally developed and brewed with this yeast. Papazian had "Cry Havoc" in his yeast stable since 1983.

He has used it nearly continuously since 83, sometimes pitching multiple batches on top of a cake, sometimes washing or not washing, etc. In a basic brewing podcast iirc last year he talked about how a batch of the yeast after a lot of uses picked up a wild mutation, and he noticed an off flavor in a couple batches.

Now most of us would prolly dump that yeast. Instead he washed it, slanted or jarred it (I can't recall which,)marked it, and cold stored it, and pretty much forgot about it for 10-15 years. He had plenty other slants of the yeast strain, so he left it alone.

Well evidently he came across that container of yeast, and for sh!ts and giggles made a beer with it. Evidently after all those years in storage, the wild or mutated yeast died out leaving behind a few viable cells of the "pure" culture, which he grew back into a pretty hardy strain...which iirc is the culture that White Labs actually used for their cry havoc...because of it's tenacity and survivability.

He's been using his yeast constantly for decades, in various strains.....

It really to me, just goes to show once again how really hard it is to f up this beermaking, and that to give the yeast the props they deserve.

But my biggest question is why the heck is your tone so hostile? You seem really really pissed about something?

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Like my snazzy new avatar? Get Sons of Zymurgy swag, here, and brew with the best.

Revvy's one of the cool reverends. He has a Harley and a t-shirt that says on the back "If you can read this, the bitch was Raptured. - Madman

I gotta tell ya, just between us girls, that Revvy is HOT. Very tall, gorgeous grey hair and a terrific smile. He's very good looking in person, with a charismatic personality... he drives like a ****ing maniac! - YooperBrew

MalFet

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I dig it, daddy-o. I've made very similar statements myself, even in the last day. I would say the standard advice is more in the league of one month, but of course that depends on many factors and a gravity reading is the only real guide. I've left big beers on yeast for several months with no ill effects to the beer, but that's a different question than the viability of the yeast underneath.

Yes to all your questions that can be answered with a yes, and it's complicated to the ones that can't. From my understanding, under ideal circumstances, yeast can stay dormant indefinitely (practically). There are stories of yeast under oil slants that are 60-70 years old and still alive. That said, there are many factors that make this unrealistic under most circumstances: heat, UV light, temperature changes, other hostile critters, hydrostatic pressure, oxidation, osmotic imbalances, etc.

Main thing is sanitation. If you look at the messages about yeast ranching, they all emphasize the need for sterilization (rather than just the sanitization that is sufficient for most homebrew purposes). If you are trying to keep a population of dormant yeast, even a small initial bacterial population can wipe you out. The fridge doesn't fix this problem, but it slows metabolic rates to a crawl and thus keeps the bacteria from taking over.

Low population itself is not a problem. Good plating techniques involve building a starter from as few as a single cell. It's a technical process, though, and there are many reasons that you want to make sure that you pitch a proper amount of yeast.