Growing yeast

[Smitty27]

I've just started to try and grow yeast from left over liquid vials from my last batch. Right now I've got a jar of WL1 and WL530 that seem to be doing well and reproducing. How long do I need to leave them in the jar before I should drain off the wort and start a new batch to produce more yeast? I figured they would eventually need a new solution in order to keep reproducing or will they continue to reproduce in the same solution?

I found this picture on the site that is very close to what I have. I started out with only a very thin layer at the bottom and it is currently the same as the picture below. My other question would be is this enough to pitch in a 1 gallon batch or a 5 gallon? I'm currently only doing 1 gallon test batches until I get something I really like and then will step up to 5 and would like to have enough yeast to use in a 5 gallon batch?

 

[LarryBrewer]

Technically, after harvesting yeast it is no longer growing. What you are seeing is the yeast settling out in the bottom of the jar.

In order to generate more yeast, a starter is needed. Typically this is done with DME, boiled for 15 minutes, resulting in a solution that is about 1.036 in gravity. Some people also make extra wort on brew day and use that for their starters.

You are okay keeping washed yeast in the fridge for 2-3 weeks. I have tried to push this as far as several months, but had less than optimal beer as a result of using old yeast.

As for how much yeast is there, the estimates range from 1B to 5B cells per milliliter. That is a pretty huge range, and a lot of factors go into it.

In terms of how much yeast you need for a batch, I think you have plenty for 1 gallon, but not sure about a 5 gallon batch. The yeast required depends on the desired pitch rate, the volume of wort, and the gravity of the wort (high gravity beers call for more yeast). See our yeast pitch calculator for more details:
http://www.brewersfriend.com/yeast-pitc ... alculator/

 

[Smitty27]

The yeast I have didn't come from a fermented container but a fresh vial. Since I'm only doing small 1 gallon batches I don't pitch all of the yeast when I buy it. So I figured I see if I could make more of the small amount that I have.

I made a starter by boiling the water and sanitizing everything and mixing in some DME. I figured I would have enough for another 1 gallon batch but I'd like to expand what I have into making several 1 gallon batches. If I were to make a few more starters and pour parts of what I have now into each of them would that work or does something else need to be done?

Once one of my other containers gets done with primary I'm going to try and wash that yeast and reuse it but for now I figured I'd try and play with the small amount that I had.

 

[LarryBrewer]

Sounds like you are doing it right. You can estimate how much yeast is being grown based on the size of your starter and the yeast pitch calculator. From there, splitting it up make sense to me. Just make sure to decant off the liquid on top and be sure the yeast gets in to the fermentor in the right amount.

 

[Smitty27]

Using the yeast calculator it shows that one of the jars I have should be good for a 5 gallon batch or the values are wrong. The only thing I'm not sure of is the density. If I drop the density to .6 billion/ml I'm still good to go but seeing as I'm super new to this I don't know how dense these things usually are.

Thanks for all of the help by the way!

 

[LarryBrewer]

Stick with 1B cells / mL to be safe. However, don't count the liquid above the slurry, just count the grey stuff at the bottom. You might have 100 mL total?

It occurs to me we should change the slurry volume unit to ml...

 

[Smitty27]

Awesome, that makes sense! Now I just need a container that has ml markings on it to make things easier. Thanks for the info!