Harvesting Yeast - When do I have enough?

I searched for similar threads but didn't find an answer to my specific question so please forgive if this has already been answered elsewhere...

When harvesting yeast from a commercial beer how do you know when you've reproduced enough yeast for a 5-gal batch?

Here's what I've done so far:

• Made a small starter wort, added it to a sanitized flask
• Sanitized bottles that contain commercial beer (Bell's Amber Ale)
• Pour most of the beer into a glass, leaving a little bit in the bottle
• Pour remainder from each bottle into the flask (I used four bottles of beer for this)
• Cover flask with sanitized foil and set in a warm spot to ferment
• Drink the beer poured off from the previous step

I did this last night and today I can already see a small amount of krausen and some sediment on the bottom of the flask so I think it's working!



So back to my question: once I pitch this yeast slurry to a new starter wort a few times to build up the yeast... how do I know when I have reproduced enough yeast to make a 5-gal batch of beer?

Mr. Malty says I need 233 billion yeast cells, or 114 ml of yeast for the beer I intend to make. (Two Hearted Ale clone, OG = 1.064)

Note: I used Bell's Amber Ale for the yeast harvesting because I read elsewhere that Bells uses the same yeast strain for most of their ales and the Amber Ale has a lower ABV so the yeast from this beer should be less stressed than the yeast from the Two Hearted Ale.

Thanks for any advice you may have.

That's an excellent question, and I'm not sure I can answer it with any certainty. I think to hit the Mr Malty numbers with confidence you would have to have some pretty sophisticated equipment.

What I have done for several years is to make a one or two, rarely a three step starter until I get 1/8 to 3/16ths inch of yeast on the bottom of a 2000ml flask, or a quart jar. All I can say is that this "eyeball" method has never failed me. I'm sure there are better approaches but once I get a nice solid layer around this thickness, I'll pitch it and it has always worked for me. 90% of the time I can get this "thickness" with dregs/lees out of two bottles and stepping it up twice, a quart of wort at a time.

You don't need super sophisticated equipment to do this. All you really need is something to make precise measurements (i.e. pippette or syringe and something that is at least 250ml in volume).

Start off your dregs in about 10ml low gravity starter wort (1.020) to reproduce healthy yeast, and let that ferment to completion. Add that to 250ml of more low gravity starter wort and let it ferment out to completion. In your 2L starter, add the 260ml of fermented starter wort to 1L of normal gravity starter wort (1.040) and you should then have a good amount of yeast to brew your beer.

New yeast washer here, if Mr Malty says I need a 100ml and my yeast wash jars each have about 25ml I've just been dumping all 4 into a starter, waiting 48 hours and pitching.

Are you saying I could just use 1 jar and keep building the starter to reach 100ml?

I usually start with the dregs and a mason jar (or pickle jar, something maybe pint sized) and do about an 8oz starter for the first go, then decant and pitch into a starter of approximately double the volume a few times until I'm at 2000ml assuming a high gravity wort or just leave it at 1000ml for midrange stuff.

this is great info for i am going to brew an oberon clone and try to make a starter for this. i was also lucky enough to find a six of oberon on a store shelf around christmas for which to get my yeast even though they say they brew with the same yeast in each beer.

evilhomer said:

New yeast washer here, if Mr Malty says I need a 100ml and my yeast wash jars each have about 25ml I've just been dumping all 4 into a starter, waiting 48 hours and pitching.

Are you saying I could just use 1 jar and keep building the starter to reach 100ml?

Click to expand...

What you are currently doing (pitching 4 25ml jars into your starter) isn't wrong, and if it's working for you...by all means keep doing it.

What I was saying in my other post is that if you were going to go straight from a bottle to a brew a week or week and a half later you should use those steps (or just getting enough for a future brew farther out).

You could also just use one jar, but you would then have to take into account the rule of diminishing returns that is explained a lot better than I can do here in the book "Yeast." Take a look at the Mr. Malty FAQ, and in particular the last question, which is a decent answer to that question and give you a good basis to ask some more questions.