repitching yeast and fast ferments...

There are a lot of threads on here from tiume to time asking about repitching on yeast cakes and the like.

Here's a little info on how this works sometimes...

A couple weeks ago, I brewed an IPA. I pitched some washed slurry from a previous batch of Wyeast 1098 British Ale yeast. It was a large amount of slurry and the ferment started very quickly (lots of airlock activity within a couple hours.) Within 3 days (probably less), the kreusen had fallen and airlock activity almost stopped.

Monday, I racked that IPA, and within minutes pitched an outmeal stout onto that yeast cake. It was bubbling like mad through the blowoff tube within a half hour. 24 hours later, the kruesen had fallen and bubbling had almost completely stopped.

One caution: these fast ferments generate a lot of heat: you want to keep your primary in a cool enough place for that first day or two that an extra 6 or 7 degress won't put you over the temp range for your yeast.

This is for those who want to re-use a yeast cake. Your yeast health will deteriorate each time you rack wort onto the same yeast cake. For healthy yeast oxygen is absolutely necessary as are minerals. Magnesium and Zinc are very important and the list goes on. Great success can be achieved following cweston's advice but after 2-3 uses that yeast cake will be cooked and it's better to take the yeast wash them and then make a starter where you can provide the necessary nutrients for a nice healthy starter. Don't be fooled by the sheer number of yeast cells. A healthy culture of fewer numbers will out perform a sickly culture of great numbers. Just my $0.02

runhard said:

This is for those who want to re-use a yeast cake. Your yeast health will deteriorate each time you rack wort onto the same yeast cake. For healthy yeast oxygen is absolutely necessary as are minerals. Magnesium and Zinc are very important and the list goes on. Great success can be achieved following cweston's advice but after 2-3 uses that yeast cake will be cooked and it's better to take the yeast wash them and then make a starter where you can provide the necessary nutrients for a nice healthy starter. Don't be fooled by the sheer number of yeast cells. A healthy culture of fewer numbers will out perform a sickly culture of great numbers. Just my $0.02

Click to expand...

Agree: this third batch on this yeast will be the last for me, and the wort repitched on that yeast cake was very well aerated.

I figure getting 3 batches (you can do more, if you split the harvested and washed slurry) brings the cost of liquid yeast down to roughly the same as dried.