Reusing Yeast Cake

[gimpmeister]

I've heard that you can reuse the yeast simply by racking the beer to your secondary and the fresh wort onto the yeast cake in the primary. I was planning to do 2 beers both using an ale yeast and wondering if I would pick up undesirable flavors in my second beer if I did this.
The first beer is a variation of "Cherries in the Snow" using raspberries and black berries in place of the cherries (Joy of Home Brewing recipe).
The second is a bold experiment I call "Hot Blonde Oatmeal Stout". Starting with toasting the oatmeal and using it as a partial mash before adding my extracts. Then I would add a quart of cold brewed Starbucks Blonde roast when I rack to the secondary.
Could I get the same effect in the first beer if the berries were frozen then added to the secondary? And if I did that would it be better to just add them and let them thaw or to muddle them?

These would be my 3rd and 4th batches as right now I have done one brew from a kit and one batch of cider, neither ready to bottle yet.

 

[progmac]

the finished yeast cake has 5x or more yeast than you want or need. you can use it, but first dump about 3/4 of it down the drain

 

[stonebrewer]

I never have done this but know plenty of people who have. I usually just do a quick yeast wash and store the yeast in a sanitized (by boiling) mason jar in the fridge until I am ready to reuse it. Works great and I have never detected a flavor issue in doing this. Good luck!

 

[boydster]

the finished yeast cake has 5x or more yeast than you want or need. you can use it, but first dump about 3/4 of it down the drain

This is great advice. Or save the remaining yeast in a sanitized jar under some beer and get ready to brew a few more batches in the next couple weeks.

 

[skw]

I have done this without problems.

That said, they say you should only do this when the previous batch had a lower or at most equal OG than the new wort.

 

[boydster]

Directly pitching on top of a full yeast cake typically means little or no cell division takes place, leaving mostly (or possibly entirely) older, scarred cells to do the fermentation. That could result in underattenuation due to poor yeast health and death (of the sickly yeast, not the brewer).

If you brew a 1.030 session beer followed by a 1.100 beer, you could potentially use the full yeast cake and have a healthy fermentation. But outside of that scenario, you should really use less than the full cake.

 

[peterj]

Usually pitching onto an entire yeast cake is a huge overpitch, which can be bad for your beer. If you want to pitch into the same fermenter you can remove maybe 3/4 of the yeast cake and pitch onto that. Or you can harvest some yeast slurry and repitch that into a new ferementer. Harvesting is more flexible because you can keep it in the fridge for up to a week I think. Use this calculator to estimate good pitching rates: http://www.mrmalty.com/calc/calc.html.

You probably won't be able to detect any flavor carryover since your second beer will be a stout. You can always look into washing yeast though.

As for the fruit, adding it in the secondary is the best way to do it in my opinion. I would at least break them open and maybe try to sanitize them somehow.

EDIT: Everything in my first paragraph was already covered before I actually posted my response. My stupid job is always getting in the way!!

 

[davekippen]

For my last brew, I racked the fermented batch off the yeast cake, filled up a sanitized quart jar with the yeast slurry from the bottom of the bucket and pitched that directly in to the new batch. Fermentation began faster than ever!

I have also pitched on a whole yeast cake - but that was for a 1.100 stout that needed a ton of yeast anyway.

If it's an average gravity batch you do not need all the yeast (as mentioned above) I think Mr Malty.com has a great yeast pitching calculator if you want to get technical about it.

 

[hbtasdfg]

You can do this but be aware if you repitch more than one time you can have issues

 

[benzy4010]

Both taste fine

 

[davekippen]

You can do this but be aware if you repitch more than one time you can have issues

I dont know if I agree with this. I have used the same yeast 5+ times, and only stopped because the fridge that I was keeping the slurry in pooped out and it warmed up.

There are lots of brewers here that use many generations of the same yeast. If you are sanitary and particular, there is no reason not to.

 

[boydster]

I dont know if I agree with this. I have used the same yeast 5+ times, and only stopped because the fridge that I was keeping the slurry in pooped out and it warmed up.

There are lots of brewers here that use many generations of the same yeast. If you are sanitary and particular, there is no reason not to.

I think he was referring to adding wort to the entire cake. If you overpitch to a degree where the yeast doesn't undergo any cell divisions, the only yeast left to do the fermentation will be old and scarred, so it would be tough to continue reusing that yeast for multiple batches due to age and poor health.

Otherwise, with a healthy pitch rate you can definitely reuse yeast several times.