how many generations is too many

I have some wyeast 1056 which i used for 2 5 gallon batches, how many batches would be the maximum batches to use it for?

Maybe 3 or 4 to be safe. As many as 10 may be pushing it, but may be fine. "Until it stops working right" is the obvious answer.

It really depends on how you treat your yeast and how good your sanitation is.

If you do starters, you could divide a vial of White Labs maybe 5 ways, do a .5L starter, then a full liter, decant it, pitch it, use it two or three times, and move on to the next vial. 15 beers for the price of one vial.

I harvest four different styles of yeast. I do a harvest of each style, once a year, from the first batch that I brew with that style that year. I use that harvested yeast the following year.
I typically make three or four different batches of beer in a row each time I use any one style of the yeasts, pulling from the cake for each of the subsequent batches.
I have used the same yeast for three years now with no problem. I think that means that at the end of the last batch of each type this year, I will be to 6 or 7 generations.
I was going to get new yeast for my brewing adventures next year and not harvest any of the yeast this year. I checked liquid yeast prices at my local HBS this past weekend and am now thinking that if all goes well this year I may harvest again.

I think 5 generations is right. The thing is, every yeast washing session you can easily harvest enough for 2 batches so each generation provides you 2 sets of "family trees". So even though you get 5 generations you actually get 5+2*4+4*3+8*2+16*1... Your welcome Princeton Review for the future SAT question.

I went at least 7 or 8 on my last US-05, no ill effects. Might have started to get a mild infection from it, but it didn't affect the beer in any way...I just noticed some film developing on the top like ice, mainly if I long primaried or secondaried.

Dang it, I messed up on my own problem... Uses = 2^5+2^4+...+2^1+2^0

greatschmaltez said:

I think 5 generations is right. The thing is, every yeast washing session you can easily harvest enough for 2 batches so ...

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You are completely right on that point. I took the yeast from my Bourbon County Stout clone. It was a half of a vial, pitched with a starter. I know that ideally you shouldn't harvest from super high gravity beers, but the yeast performed so well, and was done so quickly (within about 15 days), that I decided that I wanted to give it another opportunity.

I wound up with a full 1.75L of washed yeast slurry from that batch. And that's after pouring off the water and debris!!! Since I was brewing that night, I warmed up the yeast, put it into a 2L flask, added .3L of 1.010 wort (just enough to get them going again). By the time my AG batch was done 6 hours later, I had half an inch of krausen in the flask. I pitched half of that yeast and stuck the rest back in the fridge. I didn't even really aerate my wort because I was already pitching so much yeast, I figured the aerobic respiration phase probably wasn't all that critical. And, well... when I walked into my apartment 18 hours later after work, I freaked out. I smelled beer. My apartment reeked of beer. I was sure a corny blew, a blow off hit the ceiling, something... but no. All I found was my 1.081 IPA pounding the airlock like a beast. WHUMP-WHUMP-WHUMP-WHUMP!!!

My 2L flask has a solid 1.5 inches of yeast in it right now. And if you know how big a 2L flask is, you know that's a LOT of yeast. I'm tempted to split it into two or 3 batches because I think I'm getting close to over-pitching.

Man... paying $7 for a yeast you use one time is crazy when it's so easy to grow your own! In fact, you already do it every time you make beer!!! And given that you should be making starters anyway with liquid yeast, you should already have the equipment you need for culturing. And if you don't, a 2qt glass milk (or wine) jug, a drilled stopper, and some tin foil (or airlock, or foam stopper) is all you need... we're talking under five bucks! Although I do think it's easier to rinse yeast and repitch than it is to make a full starter. So actually, it's a time-saver to do that. And given that my average brew probably costs me twenty bucks, the yeast may be between a third and a seventh of the cost of a batch, and that cost is basically reduced to nothing. I hate to say that I'm cheap, but I'm not made of money. If I can cut out a third of my cost for a batch, I'll do it. Especially knowing that it actually makes the yeast more active and results in better fermentations.

Why not just grow your new yeast into 1.5 times what you are going to pitch and save the .5 for your next growth... No harvesting....No off flavors from previous beers... No washing....this is what i do

Make a starter and pitch the yeast cake into it. If it ferments, use it. If it doesn't, toss it

tre9er said:

I went at least 7 or 8 on my last US-05, no ill effects. Might have started to get a mild infection from it, but it didn't affect the beer in any way...I just noticed some film developing on the top like ice, mainly if I long primaried or secondaried.

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There is more risk of contamination due to dry yeast than liquid. In fact, there is a 100% chance your dry yeast has a contamination in it. Fermentis will admit such a thing and it talks about the rate of contamination in the product spec sheet. I am not privy to the exact reasons why, but it has something to do with the drying process. I also don't know why liquid yeast does not have nearly the risk of contamination but somehow it doesn't.

This is negated, I think, by the fact that dry yeast doesn't need a starter but liquid usually does. Since there is about a 100% chance your glassware is coated in microscopic filth unless you sterilize it, you're also culturing the micro vermins along with your yeast.

So I guess you're screwed no matter what.

7-8 generations is probably too much. For dry yeast, I don't think it's worth harvesting because it is so cheap.

highgravitybacon said:

There is more risk of contamination due to dry yeast than liquid. In fact, there is a 100% chance your dry yeast has a contamination in it. Fermentis will admit such a thing and it talks about the rate of contamination in the product spec sheet.

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I was reading on the White Labs website that they now are reporting QC data on their yeast batches for homebrewers, including infection rates. Previously this information was only available to pro brewers. So while I don't know what the rate of infection is for dried yeast, I believe you would be mistaken to assume wet yeast slurry is 100% pure.

7+ batches without discernable taste difference...I will take that even if there is an infection