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Using a yeast cake and aeration

Yeast & Fermentation
#1

So, I made a moderate strength 80/- (a little over 1.050 OG) with Wyeast 1728. It will be racked to a secondary next weekend. The yeast cake from this is certainly sufficient, though likely not too much, for a barleywine I’ll be making (shooting for 1.100-1.110 OG).

I’m considering using this yeast cake, but I’m a little worried about a couple things. First off, I’ve seen a lot of people pitch the beer onto yeast cakes before for strong beers like this. It seems easy, and there’s no reason it shouldn’t be sanitary (though remaining beer and traub could alter the taste). The worry that I do have, however concerns aeration.

Aeration is important for big beers, and seems to especially matter in barleywine. The standard recommendation is: Aerate when the wort is in the carboy, but before yeast has been pitched. I dutifully follow this advice, but the problem is that it will be impossible to follow if you pitch directly onto a yeast cake. There will be no time at which the wort is in the carboy, and not yet with yeast.

My two part question to this community, therefore: (1) Should I pitch onto the yeast cake and then aerate, or should I drain the wort into another carboy, and then drain the yeast cake from the carboy and pitch that into the beer? and (2) What is the reason for this advice, and are there good scientific sources which backup harm done by aerating after yeast has been added?

best & thanks in advance,
∴

#2

Good question.
I’ve recently learned that yeast need oxygen primarily for reproduction, so aeration is done to get yeast counts up. Pitching onto a cake, you should have plenty.

White and JZ in their book Yeast - which is a great book - don’t exactly answer your question, but here’s what I gleaned that seemed relevant: “If it is a very high gravity wort, more than 1.092, you must aerate with pure O2, as air will not provide a high enough level of dissolved oxygen.” And a bit later, “a second dose of oxygen between 12 and 18 hours can help fermentation speed and attenuation. - There is little to no benefit from additional aeration before the yeast has had a chance to divide once.” The later comment meaning any earlier than 12 hours after the initial aeration and pitch would be of no benefit.

Given that info, and that you’ve got enough (you apparently need 35 million cells per milliliter) with a full yeast cake, I’d suggest you aerate with pure O2 12 hours after you’ve put the wort onto that yeast cake.

There’s one other tip White and JZ have for you “at 48 hours into [active] fermentation, after yeast growth is complete, raise the temp to 77 oF for ale. The rise in temp. keeps the yeast working at their maximum.”

Hope this helps.
:cheers:

#3

Have you thought about aerate in the kettle once it’s cooled down? This is my SOP

#4

Thanks to you both!

In reply to jtb w.r.t. the quotes from “Yeast”: I should really get this book. This also serves to help confirm my suspicion that perhaps the oft-cited advice to aerate before and only before yeast is pitched into cooled wort may be on less than solid ground considering experts seem to recommend an aeration after yeast has divided even. On the point of oxygenation with pure O2, I’ll consider this when I have the money to put together an O2 system (how much does an O2 tank even cost? how long do they last?) but for now I’m stuck with air pump and HEPA filter – hopefully better than nothing.

To Baileyjoe: Yeah, I was considering this also. I’m wary to do this (though I have considered it) for two reasons: (1) that means that during the aeration the cooled wort will have additional time exposed to open air outside the fermenter, and I try to reduce this time (perhaps without necessity) as much as possible and more importantly (2) this will be a partial boil this time (unfortunately) and as such it would probably reduce the total O2 concentration potentially delivered by aeration to the cooled wort by too much to work for a potentially 1.100+ beer. I think I’ll take this advice for beers at 1.065-1.090 range though, so advice is appreciated.

#5

Think about why you aerate…it isn’t because the yeast need to breathe! :slight_smile: The yeast use O2 to synthesize sterols. The sterols are used to keep the cell walls flexible and facilitate budding. But if you pitch enough yeast, there really isn’t any need for reproduction (and therefore aeration). That’s why you don’t need to aerate when you use dry yeast…you’re pitching so many cells that it isn’t necessary. If you use a fresh entire slurry from a 1.050 batch, you’ll almost certainly have enough yeast so that you can forgo aeration.

#6

Again, thanks. Now I’m worried about whether I should instead be rinsing and pitching rinsed yeast (though time is becoming short).

#7

The advice I posted from Yeast was specifically for worts above 1.090.

I’d go with Denny’s “almost certainly” and just pitch the cooled wort (make sure it’s cooled down to say 60 f or low 60s if possible or you’ll end up with a fusel infused boozey heat fest beer) onto the yeast cake. I’m assuming you have a good sized carboy because it’s going to be a fermentation party and you could have a very large blow-off on your hands if your carboy isn’t bigger than a standard size.

I wonder why the book says pure O2 is necessary. Does it have to do with density?

If you can control ferment temps, I would heed the advice regarding raising the temp and raise the temp two days into active fermentation. It will probably be generating some heat of its own and you may want to have a swamp cooler at the ready if it heats up too much.

Drinking a beer of that caliber will require circumstances I can only dream of. Mild and bitter ales are about all my life can handle presently.

Let me know how it goes.

#8

Don’t waste your time. I’ve experimented with using rinsed and unrinsed yeast and it makes no difference in the finished beer. In addition, messing around with the yeast rinsing it is another chance to infect it.

#9

Don’t waste your time. I’ve experimented with using rinsed and unrinsed yeast and it makes no difference in the finished beer. In addition, messing around with the yeast rinsing it is another chance to infect it.[/quote]

We’re really on the same page today, Denny! I was a yeast rinser for about 2yrs, but have now switched to on rinse after reading some articles and through my own experiences. It makes no difference in the following beer and there is a much greater risk of something going wrong when rinsing.

EDIT: Not to mention the time involved in rinsing. Just rack, swirl, and fill a few santized jars. Done and done!

#10

Don’t waste your time. I’ve experimented with using rinsed and unrinsed yeast and it makes no difference in the finished beer. In addition, messing around with the yeast rinsing it is another chance to infect it.[/quote]

We’re really on the same page today, Denny! I was a yeast rinser for about 2yrs, but have now switched to on rinse after reading some articles and through my own experiences. It makes no difference in the following beer and there is a much greater risk of something going wrong when rinsing.

EDIT: Not to mention the time involved in rinsing. Just rack, swirl, and fill a few santized jars. Done and done![/quote]

:cheers:

#11

Denny,
Would it help at all to aerate?

#12

Denny,
Would it help at all to aerate?[/quote]

Not from my point of view in an average situation. The only way to know for sure would be to do a cell count, but not many of us are set up to do that.

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