Saving yeast slurry from cake for use in a few weeks

What you described works well, and this is what I usually do. You can also make a whole new starter from a little bit of the old slurry when you want to brew - this puts the yeast through fewer generations but takes a lot more time as the cake ages. Or, since 3726 is the Blaugies yeast, you can just buy a bottle of Saison d'Epeautre and make a starter from the dregs after the Wyeast gets old... about the same price as a smack pack and you get 750ml of great beer too.

 

How many step-up starters would you estimate are needed before there's enough yeast to pitch?

 

What I do is make a starter ~100B cells bigger than I need, and then collect that 100B cells to make a starter for the next time. For instance, if I need 250B cells, I'll make a starter big enough to get me 350. After it's done, crash it and later decant to ~350mL, so I can estimate I've got 1B cells/mL. I keep old WL vials around (50mL each) and use those for storage. Since it's all estimates I don't go too many generations, but it's a pretty easy way to stretch one vial/pack of yeast.

 

Three, if it's reasonably fresh; 100ml into the bottle with the dregs, step up to 500ml as soon as you see activity, then 2000ml.

 

Would you go 1.020, 1.030, 1.040?

 

I see this as "over-inoculating" (is that a word?) your starter. If you estimate as little as 500 billion cells (conservative) in your slurry and pitch that into a 2L starter you are pitching at an rate of 250 million cells/ml which is way too high. Ideally you want to be in the 25-150 million cells/ml. If you "inoculate" too high you risk little to no growth. You can solve this problem by increasing the size of the starter (but now you're talking 3-4L) or by pitching a fraction of your slurry into something more modest.

My suggestion is not to re-start every few weeks, I regularly go 8 weeks between use of stored yeast. At worst you may see a 6-8 hour lag time before it re-starts but have never had one fail. I would even consider making a mini-batch of beer as a more enjoyable method of keeping the yeast active.

It looks like lots of experience from the other posters in this thread. I would welcome input on the following: I estimate yeast I harvest from dregs to be in the range of 1.2 billion cells/ml (my rough guess). Yeast that I have washed from a cake I estimate at 2.0 billion/ml. Of course I adjust the number of cells for time, but have gone 3 months before re-starting stored yeast. I store in my fridge which is ~40F which is a mite high. Other experiences/inputs?

 

I usually end up going about 1.030; IMO, 1.020 would be better but I'm getting away with it (can only store so much sanitary wort in the beer freezer so I go a little stronger than I should at times).

 

I've gone 6 months at times with good results, but certainly not recommended (I store at ~35F). Making a mini=batch occasionally, preferably fairly low OG, is a great idea if you're more organized than me...

edit: the lag time on a 6 month old cake is super scary, but if it smells ok it will probably turn out fine.