Why is repitched yeast better?

I've heard many people say that you just end up with a better beer after repitching the same yeast. But that's all I've heard. That it's just better. Can anyone explain why? Jamil Z. says that after about the 3rd batch he's noticed that he really gets some outstanding beers.

One potential drawback is that it seems to me that it would be harder to get your pitching rate exactly right because you don't really know your concentration of yeast cells.

Lastly, could the same thing be accomplished with a "stepped" starter? By that I mean putting the yeast in a starter(with nutrient) multiple times to reduce the turn time of having to complete several full batches.

I'd presume it has to do with two main factors, cell count is optimum for volume, and natural selection. The NS bit comes from having readily available glycogen stores within the cell, the fact that the cells already know what they are going to "eat", and that the more flocculant cells are already buried at the bottom of the cake.

In 3 years of brewing, I have never pitched on a yeast cake.

This is one of the "grey" areas around here. Much like glass vs better bottle and autolysis. Personally, I'm not a big advocate of pitching onto a cake. I would rather make a bunch of small cultures from a starter and freeze them, then use those slants to make starters for other batches. But lately I've been trying to use as many different types of yeast to see their differing characteristics and find out which ones I like best.

You're correct on the pitching rate and thus some of the characteristics (flavors) that the yeast will produce. If you over pitch some of those flavors may not be developed, and if they are it will be at a less than desired quantity.

Making a huge starter won't have the same effect as repitching on a cake. Each beer imparts flavor onto the next and so you don't have a lot of that trub mixed in with a starter.

I have a question about racking on a yeast cake. What about all the crud on the side of the carboy from the original beer that was in there? Do you wash that out somehow or do I poor the yeast into a new clean carboy?

thedude123 said:

I have a question about racking on a yeast cake. What about all the crud on the side of the carboy from the original beer that was in there? Do you wash that out somehow or do I poor the yeast into a new clean carboy?

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Pour into a clean, new carboy. You don't want any of that crud getting in your next brew, it is very nasty stuff.

thedude123 said:

I have a question about racking on a yeast cake. What about all the crud on the side of the carboy from the original beer that was in there? Do you wash that out somehow or do I poor the yeast into a new clean carboy?

Click to expand...

I have never poured into a new carboy... You know that stuff stuck to the side? Yeah, the rest of it fell to the bottom and is co-mingling with your yeast. As long as your last batch was not infected, rack on top of the old cake and rig up a blowoff. I have had good success with this method.

Ok. To clarify, I wasn't referring to pitching on the full yeast cake. What I heard was best was to rinse(not wash) the yeast. This was done by putting some sanitary water into the fermenter, shaking until all material was in a slurry, and letting it sit for about 10-15 minutes. The break material and dead yeast cells supposedly drop to the bottom leaving a pretty healthy slurry on top. You decant that into graduated container(s). You can pitch as is within a week or use a starter if you need to wait longer. He distinguished this from washing which includes acid which can weaken the yeast. This healthy slurry is pitched into a clean sanitary fermenter. Seems fairly simple but was wondering if it was worth the trouble really. The guy swears it produces a better beer but didn't explain why and I was wondering if anyone knew why that might be. Oh, and he said that you shouldn't use the full volume. He said to use a pitching rate calculator because there is a certain amount of reproduction that is actually good for the beer. That in most cases, pitching the full amount of even the healthy slurry left was too much unless you were doing a pretty significantly higher gravity beer for the next batch.

Sounds like the 'Yeast Washing Illustrated' method. There's a ginormous thread here about it.

I wonder if it also has to do with yeast health? If I make, say, a 2L starter from a 100-billion-cell smack pack or vial and then make another 2L starter from a 250-billion-cell slurry/cake...the yeast in the 250-billion-cell starter get to focus more on building cell walls/glycogen reserves where the yeast in the 100-billion-cell starter had to focus more on reproduction and not as much on cell-wall-building or glycogen reserves.

I think the only benefit is you would pitch all or mostly healthy yeast cells because all of the dead cells would fall to the bottom of the container leaving lots of good yeast which would cause a really rapid fermentation.

As Belmont points out, Jamil is not talking about pitching onto a yeast cake, that would be major over pitching and although probably not as bad as under pitching it has drawbacks also.

Washing yeast is really quite simple so I would say it is worth the time. I generally just swirl the cake and left over beer around and let sit for a few mins and then dump into a big jar. Let that sit for a bit and then decant the top portion into a couple smaller jars. Let those sit for a bit longer and then decant again into a another jar. Pop that in the fridge for a couple days and you get a nice yeast cake that is trub free on the bottom. Not washing really, but separating it from the trub which I don't want to keep pitching into new batches.

From there you can pretty much decide how much you want to pitch based on your OG and what kind of starter you want to make from it. I like to make a starter the night before just to get the yeast active again before pitching.

Like GilaMinumBeer said, I am sure the theory is that you have gone through quite a few generation of yeast and the ones most suitable for beer production become dominant. Not sure how much I believe that though, since the best reproducers are not necessarily the best flavor makers. Have not gone through 3 generations of pitching though so I can't really comment on how it actually works.

If you are making the same type of batch then washing yeast should have no foul of bringing flavours over from the previous batch - unless you have something funky going on like an infection.

I plan out my batches ahead of time and will wash/rinse and re-use the yeast. I am yet to get really any major "off flavours".

I also read in BYO maybe 1 or 2 issues ago about making similar batches and the first one being a 2.5 gallon batch the second one a 5 gallon batch and then if you dare a 10 gallon batch and just dumping onto of the yeast cake (to cut the cost of yeast in 1/2 or 1/3) and planning by doing a blonde then a pale ale or something.

I tried this and just took some of the yeast out of the cake prior to dumping in my 5 gallon batch of Pale Ale (ontop of a blonde ale that then went to secondary ontop of fruit) I then took that small amount of yeast I took out and made a starter with it.

The pale ale dumped ontop of the yeast tasted fine as well and fermented fully and quite quickly too. Is it the most accurate way to make beer? no, but I'm also making beer in my kitchen and it does taste pretty darn good.

I think the reasoning for re-using yeast (other than the cost factor) is when its used in the same recipe/style natural selection will take its course and weed out the bad yeasties and the good yeasties will survive. This then means the good parts will keep reproducing itself and less work is done to get rid of the bad.

if you want to do specific yeast cell-counts and all that jazz : if there is a will, there is a way even with re-using yeast

Thanks for the process tip steelerguy.

This is getting closer I think. So what GilaMinumBeer said about natural selection seems to make sense. Basically after a few batches the weaker cells have died off and will settle out leaving you with a higher percentage of stronger cells after each batch.

What SpanishCastleAle said may answer my question about the stepped starter. The distinction between reproduction and strengthing cell walls/glycogen storage makes sense.