Yes, my head is spinning reading this but in practice, I'm sure it will have me saying "duh".
Brilliant to record the tare weight of your empties! I'll use the tare function of my digital scale, safe to do, would you agree? DERP, your point of reference is for weighing a vessel that has the slurry in it already so can't tare it to weigh slurry only, got it.
Once you do it, you'll develop your own methods. Mine are just an example, the way I do it. Feel free to ignore or adapt anywhere you like.
Early on I discovered that weighing a vessel is the easiest way to obtain a decent sense of the amount of its content. For that, pre-weighing the tare of each vessel involved is needed. Even the weight of the lids are recorded, in case I have a jar with lid or one with a foil top.
Oh wow, I like that first calculator you linked to. It gives you option to overbuild for harvesting, brilliant. I appreciate that it recommends pitching a shaken starter into your wort rather than decanting before pitch. For me, that takes the guess work out of "is that starter beer I'm pouring off or yeast too? How much of this that's left behind will be pure yeast? How will I separate this for harvesting the rest after pitch?"
Working with either calculator gives you a good sense on how to manipulate starter volumes to get your desired cell counts. Now sometimes it's a shot in the dark if the yeast viability and activity is low. But you know you've propagated some, just not how much. Again, it's usually better to overpitch than underpitch grossly.
Re:
Highlighted in red. Where did you see that? It is typically
advised against to pitch whole starters without cold crashing and decanting, especially where large amounts of starter beer are involved. It dilutes your beer and adds bad tasting oxidized starter beer to your batch. For small amounts or pitching a yeast at high krausen to resurrect a stalled batch you can get away with it.
If you're building starters in multiple steps, cold crashing and decanting after each is the only method to keep your volumes at bay. Starter beer has nothing to bring to the party, except for topping off your storage jars to prevent oxidation (dead yeast is darker).
To concentrate the yeast into a slurry, after shaking, or better, stirring on a stir plate, place the starter vessel in the fridge for 1-3 days (cold crashing). Most if not all yeast will floc out to the bottom. Some yeasts will floc out as soon as you take them off the stir plate. Pour off the clear or mostly clear starter beer, leaving a little behind to swirl it up into a pourable slurry.
So, for generational reference, it looks like you are assuming a loss of 10% of the cells from original propagation (90b in st1 vs 80b in st2). Or did I misinterpret that? What is your purpose for noting what generation starter that particular jar contains? Are the older cells in ST1 a better/more viable collection than the "newer" cells in ST2?
Misinterpreted.
That was just an example. I just recorded the estimated cell count in that partial of st2 and is largely independent of what was in st1. In the calculator you just plug in your st1 cell count and the date it was generated. It will calculate remaining viable cells from there and how large a starter you need to generate the desired count for starter 2.
Keeping track of starter generations is useful as you don't want to exceed x amount of generations. I keep x at around 10 for starters made from starters (not used in real batch fermentations). Around 5 for reused yeast from previous batches. Or less, when I sense changes, like increased time needed to clear the beer when cold crashing, flavor, attenuation, and other factors.
So, you're saying that if I take 4 of these small jars out for a whole year, it would be necessary to bring them together into a single starter due to the loss of viability over that period of time, right?
Thanks very much!!!
Not necessarily, but it makes more sense when you have 3 or 4 jars of a stored strain in the fridge that are a year old. You may as well rejuvenate all of them at once by making a new starter from the whole lot. Their cell count is maybe only 10% of what they started with. So that original jar with st1 contained 90 billion cells is now down to 6% of that, 5 billion! If I use all 4 of those jars that at least gives me 4x5=20 billion to make my first step with, followed by a second to get my pitchable quantity plus some left over to store away again.
For long term storage and yeast banking, freezing yeast and/or slanting them are better and more manageable ways, especially when many strains are involved. Otherwise you'll have to make "rejuvenating starters" every 6-12 months, which has inherent limitations.
