When Pitching On Top of Yeast Cake...Stir?

[Pat in WV]

Should I just pour my wort and then seal up the fermenter? Or should it be stirred up?

I will be putting a Stout on top of a Pale Ale...

Thanks all for the help!

 

[Orfy]

Just pour it in.

 

[DAAB]

don't forget to aerate

 

[Pat in WV]

So...do I need an aerator (sp), or special equipment, if I am going to pitch onto an existing cake?

Sorry, I'm a Noob with a capital 'N'.

Thanks.

Pat

 

[DAAB]

You can rack to the fermenter from height to introduce o2 or whisk the cra.p out of the wort with your brew paddle. You can get wort aerators but they aren't necessary.

 

[Orfy]

It's good practice to get 02 from air into the wort so the yeast can multiply. After they multiply they then start work on the sugar.
When pitching on to an existing yeast bed you have a massive amount of yeast compared to a normal pitch. So I'd say in theory aeration is not as important.

To aerate whisk the wort up then pour it into the fermenter, this will mix O2 into it.

You don't need any extra equipment or any extra preperation than if you are doing it the normal way.

 

[Baron von BeeGee]

This is an interesting question I hadn't really considered. Yeast multiply during an aerobic growth phase requiring oxygen. However, if pitching on a cake where the cellcount may already be high enough, it would seem you could go straight to the anaerobic phase where alcohol is produced. I suppose the risk, depending on the health of your yeast and the amount of sugar in the followup beer, is do you have a high enough cellcount without a growth phase.

It seems like low aeration/oxygenation would be good to me, but I'm just rambling.

 

[DAAB]

It's inevitable that when pitching a yeast cake or onto a yeast cake you will be introducing a level of bacteria that wouldnt normaly be present after pitching a fresh starter or sachet. For that reason it's my opinion that you should always aerate a wort to minimise lag time in order for the yeast to be able to supress competing organisms.
Yeast are excellent o2 scavengers, you can't over aerate a wort with standard homebrew techniques.

 

[Baron von BeeGee]

The point of my rambling musing is that depending on the health of the yeast and the amount of sugars present there may not be a lag phase at all. If the yeast cellcount is high enough it will go straight to anaerobic fermentation (my supposition, I'm no biochemist).

But I agree some aeration probably won't be harmful. However, you do want the yeast to go anaerobic so that they begin producing alcohol.

 

[Chairman Cheyco]

But I agree some aeration probably won't be harmful. However, you do want the yeast to go anaerobic so that they begin producing alcohol.

The problem with pitching on a full yeast cake is that many of the flavors we associate with delicious ales are produced during the growth phase - which is the phase which requires oxygen. Racking right on top of an entire yeast cake will give you a beer that is well-attenuated, but may be lacking in flavor because there has been no growth phase.

 

[Evan!]

The problem with pitching on a full yeast cake is that many of the flavors we associate with delicious ales are produced during the growth phase - which is the phase which requires oxygen. Racking right on top of an entire yeast cake will give you a beer that is well-attenuated, but may be lacking in flavor because there has been no growth phase.

I've done it exactly once, with a hefe, and it was anything but lacking in flavor. Not saying this proves or disproves anything, just putting it out there.

 

[knipknup]

I aerate my wort first (by simply pouring it from kettle to bucket twice) then I siphon right on top of the yeast cake that is still in the Primary. I didn't pull the yeast out or anything. After I siphoned the first brew out of the primary, I put the airlock back on until the second batch was cooled and ready. I didn't put the siphon hose all the way down to the bottom of the carboy but a few inches from the bottom. This mixed some, but the yeast will start doing its own mixing within an hour.