Yeast cake pitch start

[sdillow]

Tried pitching on a yeast cake tonight, yeast was WLP001 and wort was 1.062 black IPA. Just checked on her and it's bubbling away already after 1.5 hours. A guy at my LHBS had advised me against it saying it's too much yeast, I guess causing off flavors? What's the concensus here?

 

[kyleobie]

What was the OG of the previous beer?

I have had numerous people tell me not to pitch a smaller OG beer on a big yeast cake, but the results have always turned out fantastic.

 

[nefarious_1_]

From Mr. Malty:

I know a number of people dump a new batch on top of the yeast cake, but you're not going to get the best beer that way. Yeast do need some growth to result in the right kind of ester profile, etc. While too big a pitch is better than too little, it is pretty easy to figure out how much you need and pitch just that.

According to Fix, in a slurry, only about 25% of the mass is yeast solids. Of course, if there is a lot of trub in there, you have an even lower percentage of yeast solids. The bad thing is that you can't tell how viable that yeast is, unless you have the equipment to properly test and count it. So this is where it gets a little bit like black magic. There are a number of factors that affect the viability of a given pitch of yeast. How old is the yeast? How stressful was their last fermentation? Have they had the proper environment and nutrients for successful reproduction or are they too scarred and tired to go on?

In short, calculate how much yeast you need, rinse it, then pitch the proper amount. It's incredibly easy and you'll make better beer. Sounds like a no-brainer to me!

Of course, there will be a flood of people talking about how they repitch onto a cake all the time and still make beer. According to Jamil, Chris White and some others, it seems this will not result in the best beer possible. Ultimately, it's your choice to decide though... Check out some of the information in "Yeast."

I've also heard it's common practice for breweries to re-use yeast, but I believe they rinse it and measure a proper amount before repitching as well.

 

[otis34]

I've done it and didn't have any issues. It is a common practice among some homebrewers.

I have also heard LHBS staff try to sell me another pack of yeast because I was doing a 6 gallon batch instead of 5. That kind of salesmanship really irritates me.

 

[Jester]

Ironically I had a conversation with the owner of my LHBS about this exact subject. I was getting ready to buy another vial of yeast for this upcoming brew and he remembered me brewing a somewhat similar beer a few weeks earlier and recommended me just racking ontop. I have never done this, but I have been wanting to wash/reuse yeast due to it being one of the more expensive ingredients. I'm hoping it turns out well....