Yeast Cake vs. New Yeast (why does a yeast cake work)

[eauclairedan]

Just a quick question on something I don't undestand:

A lot of people I know (and on this forum) rack onto yeast cakes from a recent batch, and I too have done this with success for big beers. Often times this has come from a single 11.5g packet of dried yeast. On the contrary, according to literature and forums, "bigger" beers should have 2-packets pitched. Can someone explain to me how a yeast cake from one packet is sufficient but one packet fresh would not be? Thanks!

 

[m00ps]

a yeast cake contains orders of magnitude more yeast cells than a packet. The yeats re[produce as they feed and make beer. Normally, even for big beers, you wouldnt want to pitch on top of an entire yeast cake as it is waaaaay overpitching.

personally, I dont like the idea of pitching on top of a yeast cake as those yeast cells are not as healthy and clean as I would like. They have been exposed to hop compounds and gone through the stress of an entire fermentation. I would recommend harvesting from a yeast starter if you are looking to not have to acquire new yeast for each batch

 

[rhys333]

Just a quick question on something I don't undestand:

A lot of people I know (and on this forum) rack onto yeast cakes from a recent batch, and I too have done this with success for big beers. Often times this has come from a single 11.5g packet of dried yeast. On the contrary, according to literature and forums, "bigger" beers should have 2-packets pitched. Can someone explain to me how a yeast cake from one packet is sufficient but one packet fresh would not be? Thanks!

You might want to read the Simple Yeast Storage Procedure sticky at the top of the fermentation and yeast section. The trick is to pitch a reasonable amount of healthy yeast. Its pretty forgiving stuff though, so as long as you follow a couple basic rules you're on your way to making excellent beer. Pitching onto an entire yeast cake is definately an over-pitch (enough for 4-5 separate brews), and importantly can carry forward flavors from your previous batch. Typically, a 1/3 pint of yeast slurry is plenty to ferment a new batch.

 

[MattyIce]

I have pitched on plenty of yeast cakes. Makes for a fast, violent fermentation...and fantastic beer. I have never done side-by-side test batches of cake vs starter though. I also have never reused a cake a second time.

 

[Mer-man]

And I would add that as long as your fermentation wasn't in the upper range of ABV for the yeast, it is not going to be stressed. It is going to be content and well fed, because you gave it aerated delicious wort under ideal temperature conditions, right?

But yeah, pitching on a cake is waaay overkill.

 

[eauclairedan]

Thanks for the replies guys.

 

[nettekdl]

It is not stressed as long as the first batch was no a high gravity brew, it is healthy and very viable. The reason it's enough yeast is because it has reproduced exponentially from the single pack that you pitched originally. As for the last part of your question I don't follow what you are trying to ask

 

[eauclairedan]

Thanks for the reply. To clarify my last question:

As you stated, the yeast multiply exponentially during a fermentation, correct? So why would anyone every need to pitch 2 packets of yeast for a "big beer"? For example, some recipes suggest adding two packets for OG's over 1.08. Shouldn't the yeast multiply exponentially and convert the high gravity?

 

[MattyIce]

Thanks for the reply. To clarify my last question:

As you stated, the yeast multiply exponentially during a fermentation, correct? So why would anyone every need to pitch 2 packets of yeast for a "big beer"? For example, some recipes suggest adding two packets for OG's over 1.08. Shouldn't the yeast multiply exponentially and convert the high gravity?

Several off-flavors develop during the reproduction/propagation phase. If conditions are ideal (low-moderate gravity, good temp, ample oxygen present, etc.) low pitching rate is less likely to cause an issue. This is basically how starters work. You can propagate a population from just the dregs of a bottle up to large, pitchable starters by giving the yeast ideal reproduction conditions. In high gravity situations, the yeast is more stressed. They will multiply less, produce off-flavors and sometimes under-attenuate. Stresses from high gravity is recognized by those that pitch on to cakes as many of us will not reuse a cake that has been used for a 1.070+ beer.

From the reading I've done, professional brewers seem to pitch at rates at least 2-3x what us homebrewers do. I think this is how they are able to turn around regular gravity ales reliably inside of a couple weeks.

I learned a lot from the book Yeast by Jamil Zainasheff