In an effort to save time when re-starting yeast, does anyone see a problem with sort of doubling up on how much yeast you start? For example, for a 10 gallon high gravity batch, could I grow enough cells using the following start up steps:
start three 10ml initial steps (24 hours)
add into 300ml of wort on stir plate (24 hours)
pitch to 3l starter on stir plate (36-48 hours)
Or possibly even breaking it down into three separate 100ml steps to pitch to the 3l step?
Any thoughts or input?
That scheme should work. All your steps are within the 10x increase recommended by Chris White and others. The only issue I can see, making 3 initial 10ml cultures triples your chance for contamination at the most critical step.
That said, I have been looking into and experimenting with inoculation rates for step increases. With all due respect for the 10x increase between steps there are other camps out there that would recommend a smaller fold increase, i.e. a higher inoculation rate. Somewhere I came across the 4 - 7 rule. I think it is practiced in Europe. Anyway, I have tried this with great success. The 4 - 7 rule says, step increases should be no less than 4x and no more than 7x. As it turn out, by following this rule, my steps are in log phase within 12 - 14 hours at 70 F under good aeration. Certainly there will be strain differences but my Belgian strains are typically ready in 12 hours. This saves a lot of time for preparation (even with the fact you may need an extra step) and allows a smaller window for any contamination to increase.
So consider this scheme:
Start a 10ml initial step (12 -24 hrs) 2 big loop-fulls from a fresh slant will be in log phase in 12 hrs, older cultures may require more time. Even better, start a few days earlier (4 for my strains) by dilution streaking from your slant to a plate and pick 4 -6 single colonies (you can be sure these single colonies are contamination free and are in great health).
Add to 60ml for a total of 70 ml (12 hrs)
Add to 400ml for a total of 470ml (12 hrs)
Pitch to 3l for a total of 3470ml (12 hrs to log phase)
A word of caution on pitching cultures grown from slants: This is practically the same method yeast labs use to produce yeast. Lab produced yeast is the healthiest most viable yeast possible and therefore require a lower pitching rate. And because you are producing them in your own lab, they are the freshest yeast possible. White Labs and Wyeast both recommend pitching about half the rate of lab produced yeast compared to re-pitching from a previous batch. So on average you would want to pitch 500,000 cells/ml/degree Plato. So for a 1.060 10 gallon batch you should pitch 283 billion cells. I increase that to 600,000 cells/ml/degree Plato for my higher gravity Belgian ales (~1.075). If you were doing a big lager you may want to use 750,000 cells/ml/degree Plato.
Concerning yeast yield when growing up from slants: Your yield may be much higher than what yeast calculators would predict. In the literature and my experience you can produce as much as 300 million cells per ml in a well aerated culture at 75 degrees F. 200 to 250 million may be good estimate if you can't count cells but estimate less if you are in doubt about your aeration. If your stir plate can make a vortex that touches the stir bar, estimate 200 to 250 million cells per ml. I just scored an orbital shaker and my last count was 292 million cells per ml!
So at 250 million cells per ml, your 3470ml culture would contain 867 Billion cells!
I'm saying all this because I learned the hard way. I kept building bigger and bigger cultures thinking I was under-pitching but my Belgians just kept getting cleaner and cleaner, lacking the esters I was looking for. After I gained the ability to count cells, I realized I was over-pitching by >2x.
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