[dllipe]

I've seem a few videos where brewers save the yeast cake from primary and use it for future batches/starters.  What are the primary benefits to this?  Also, I thought that the yeast by this time would be worn out, how does this add value to a yeast starter?

[Slowbrew]

As long as you use fairly quickly, pitching on a yeast cake is like making a huge starter.  You get an almost instant start to your fermentation and lots and lots of active yeast.

You only want to reuse it directly one or two times or you can start getting off flavors.

If you are looking to reuse yeast over longer periods of time you could look up yeast washing so you separate the yeast from the tube.

Paul

[hamiltont]

The benefit is not having to buy yeast for every batch. Basically each batch of beer it a huge starter for the next batch. They're not worn out per say. They've just consumed the bulk of the sugars and then take a nap.

There are various schools of thought around the reuse of yeast but here's how I do it. I like to plan my brews around reusing the yeast from a prior batch. Generally 3-4 times. For most Ales, a half pint of fresh thick slurry per 5 gallons is adequate.  For Lagers it's usually 1 pint of thick slurry.  www.mrmalty.com is a great source for pitching rates. I use a sanitized pint canning jar to store the thick slurry.  It can be kept in the fridge for up to a week and then pitched directly into the cooled wort without a starter. With this process I only have to pitch new yeast for the first batch. YMMV...

Cheers!!!

[etbrew]

Like others said saving your yeast means you don't have to buy as much and it acts like a huge starter. 

If I'm going to save it I will leave enough liquid in the fermenter so I can swirl up the yeast cake and pour it into a clean mason jar, put some foil on top and store in the fridge. 

If I want to make a big beer like a barley wine I will brew say a pale ale or IPA and rack the barley wine right on the yeast cake from the IPA.  Not only does this save you from making a starter for the barley wine it provides plenty of yeast to fully ferment a high gravity wort.

[The Professor]

Do it.
 If your sanitation is good, you should have no problems.  I do it routinely.   For a wet yeast user, buying a new tube or smackpack is just insane.   When you do repitch though, most times just 1/3 of the slurry will be plenty for a healthy ferment.  Use the rest for another batch or dump it into your next boil.   I've stored slurries in the fridge for 3-4 weeks and reused them with no problems whatsoever.

FWIW, I have repitched slurries through 9 or 10 brews with no problems, and have had no off flavors (a few times I repitched well beyond that with no issues, but these days figure I shouldn't press my luck).   

[davidgzach]

This is definitely one of the best ways to cut costs and add a new technique to your brewing.

I couldn't find any Mason Jars, so I have been using 1Q Powerade containers.  I sterilize (not sanitize) them with a healthy dose of bleach, soak and then rinse 4-5x with hot water.  Sterilize your funnel and wipe the edge of your fermenter with a paper towel sprayed with StarSan or equivalent.  Swirl up the cake in the remaining beer and pour in to 2-3 containers.

A big part of this is labeling everything so you know what beer it was in previously, how many generations and the gravities of each beer.  You do not want to pitch slurry from a very high gravity beer in to a much lower one.

I've kept slurry for up to 4-5 months and then usually start over.  BUT, that's not saying you cannot go longer.  You have to "burp" them every few weeks as the yeast is still producing some CO2 (especially lager) so take a whiff.  You'll know if it's going bad or not pretty quick.  You can also make a starter instead of direct pitching the slurry.

It's fun!  Give it a try and then move to washing......

Dave

[hubie]

I sterilize (not sanitize) them with a healthy dose of bleach, soak and then rinse 4-5x with hot water.

I didn't think you could sterilize with household bleach, at least not without lowering the pH with some acid, or without using it at some uncomfortably low dilution ratio.

[davidgzach]

I'll tell ya.  I've heard, like about everything with this hobby of ours, about every side of this one.  BUT, I can say that I fill each bottle with 1/4 bleach, fill with HOT water and soak for 15-30 minutes.  I then rinse out while shaking vigorously with HOT water to make sure none of the bleach is sticking to the plastic.  In the dozen of yeast cakes I have reused, I have not had a single issue (as I knock on wood (my head)). 

[davidgzach]

You made me think more on this one, so I found this online in "Brewing Techniques"

"Although bleach is a good sterilizing agent, it is also corrosive (especially to stainless steel) and can be toxic. I recommend rinsing off residual bleach with hot water or some other sterile solution rather than leaving it on your equipment. Besides potentially adding an unwanted off-flavor to your homebrew, residual bleach may kill or reduce the viability of your yeast."

Hence why you need to rinse thoroughly.......

Dave

[tschmidlin]

Hence why you need to rinse thoroughly.......

Which is also why the vessel can no longer be considered sterile.

[The Professor]

Hence why you need to rinse thoroughly.......

Which is also why the vessel can no longer be considered sterile.

Right. 
Yeasties need a bit more  protection to be sure, especially if any time is going to pass before re-use. 

When I have a batch fermenting, the day before racking time (from the primary) I take one of my large flasks, boil 800ml of water in it for 15 minutes, cover it with foil, and let it cool.  After racking the beer (which in my case is almost always to a secondary), I dump the now cooled water into the carboy with the yeast, mix  it well, and dump it back into the flask.
Covered with foil (and a rubber band if one is handy) it lives in the fridge until I'm ready to use it for another ferment, generally within a couple weeks.   I've  found washing the yeast to be  unnecessary, even with my habit of 8-9 repitches.
20+ years of doing it that way  has only ever resulted in a lost  crop twice  (once due to a fridge malfunction, and once when I was on tour and waited too long to reuse it for another brew after I returned home). 
Other than that, just keeping it simple and keeping it clean has served well.

[hubie]

You made me think more on this one, so I found this online in "Brewing Techniques"

"Although bleach is a good sterilizing agent, it is also corrosive (especially to stainless steel) and can be toxic. I recommend rinsing off residual bleach with hot water or some other sterile solution rather than leaving it on your equipment. Besides potentially adding an unwanted off-flavor to your homebrew, residual bleach may kill or reduce the viability of your yeast."

Hence why you need to rinse thoroughly.......

Dave

Sorry, I wasn't clear.  I was coming from the angle of sterilize vs. sanitize. I was wondering whether you could cross from sanitize to sterilize without using acid or using low dilutions (as compared to the usual amount suggested for homebrew use).

[davidgzach]

Hence why you need to rinse thoroughly.......

Which is also why the vessel can no longer be considered sterile.

True enough.  But a previously sterilized container, only rinsed with 140F water has treated me very well.  I have not lost a cake yet. 

Totally just jinxed myself.......

[davidgzach]

Hence why you need to rinse thoroughly.......

Which is also why the vessel can no longer be considered sterile.

Right. 
Yeasties need a bit more  protection to be sure, especially if any time is going to pass before re-use. 

When I have a batch fermenting, the day before racking time (from the primary) I take one of my large flasks, boil 800ml of water in it for 15 minutes, cover it with foil, and let it cool.  After racking the beer (which in my case is almost always to a secondary), I dump the now cooled water into the carboy with the yeast, mix  it well, and dump it back into the flask.
Covered with foil (and a rubber band if one is handy) it lives in the fridge until I'm ready to use it for another ferment, generally within a couple weeks.   I've  found washing the yeast to be  unnecessary, even with my habit of 8-9 repitches.
20+ years of doing it that way  has only ever resulted in a lost  crop twice  (once due to a fridge malfunction, and once when I was on tour and waited too long to reuse it for another brew after I returned home). 
Other than that, just keeping it simple and keeping it clean has served well.

I think your last sentence is the point here.  Keep it simple, keep it as clean and sanitized as possible (I will not make the sterilized mistake again) and you'll be fine. 

[tschmidlin]

Hence why you need to rinse thoroughly.......

Which is also why the vessel can no longer be considered sterile.

True enough.  But a previously sterilized container, only rinsed with 140F water has treated me very well.  I have not lost a cake yet. 

Totally just jinxed myself.......

  I'm sure it will be fine, I was just saying it wasn't sterile.  Keep with the procedure that is working for you.  If it's not broken . . .