stepping up BIG starters

OK. There's lots of talk of Jamil's and others suggestion that homebrewers waaaaaaaaaaaay underpitch and the chart from classic styles suggests starters that are half as big as the batch size (e.g., 9 L starter (2.3 gallons) for a 5 gallon batch where 4 vials are called for) in some cases. So, i've been trying to aim for proper pitching rates and, as such, doing starters. Obviously, spending 9-30 bucks on yeast is difficult to sustain so I need to know more about building starters. also, I'm trying to bank frozen yeast and am thinking about how to build those out. I have had good luck with yeast, building small starters, etc. but am interested in proper pitching rates and seeing for my own self how this changes my beer.

My original thoughts were that it was the sugar that made the yeast grow in volume (or abundance or number of cells) so I tried to be tricky and build a 2 L starter, decant it and referment it with 2L of new wort but didn't notice an apparent difference in yeast volume (number of cells) at the end of the second fermentation cycle relative to the first. I was trying to reduce the vessel size and the need to use multiple vessels in the build up process. Plus the logistics of larger volumes of wort (heating, chilling). Well, my first starter had apparent increase in yeast volume but the second ferment (after decanting and replacing wort with new) did not seem any bigger than the first (of course, I didn't measure anything here so I don't really know - it could have been an illusion). I'm guessing I've produced evidence that VOLUME of the WORT is the determining factor when growing yeast and not the availability of food? If it were just the availability of sugar regardless of volume wouldn't my starter have doubled, or at least increased in yeast volume, in each cycle?

What is the truth, here? If it's volume, why do we need to BUILD starters rather than just, say, go from 1 WL vial to a 3 gallon carboy of fresh wort? Can't I just take my 10 ml yeast bank starter and pitch it in 3 gallons of wort and then pitch that? At what point are we just making a cake to pitch on, and perhaps better off just pitching on cakes - building up styles or strengths as many suggest (e.g., mild->bitter->english ipa->barleywine). I've read a lot on the old intraweb about this issue but never really seen anyone address what is going on in a 'population dynamics', carrying capacity, limiting resources, etc.
Thanks for your expertise and thoughts

cb

My guess is that yeast cells increase with volume due to the fact the amount of o2 increases with volume and before reproducing the yeast scavenge all free available o2 first. Did you reintroduce o2 into the 2L starter you fed with more wort? If not, my guess is you didn't see a marked increase in cell counts because the yeast didn't reproduce because of the lack of o2. I think another problem you might expect with feeding a 2l starter with more wort and more o2 is that if there is already a proper amount of yeast and they then reproduce more there wouldn't be enough nutrients in solution for them to not metabolize things they normally wouldn't thus producng off flavors. This would be the problems associated with over-pitching. So I think these are the reasons yeast are stepped up with increased o2 and increased sugar/nutrients.
I wonder what would happen if you started with a 1.040 gravity 2L starter and after the yeast settle out you reintroduced more o2 and then 'fed' the starter with 1.080 gravity wort, which should kick the yeast into reproducing yet not causing off flavors due to the increased sugar/nutrients. But then you get the problems associated with struggling yeast in a high gravity solution, so I guess you are better off doubling/tripling the the volume of a 1.040 wort which increases available nutrients but keeps the gravity the same.

This is just a guess. Since nobody else answered I figure I'd take a stab at it.

mandoman said:

OK. There's lots of talk of Jamil's and others suggestion that homebrewers waaaaaaaaaaaay underpitch and the chart from classic styles suggests starters that are half as big as the batch size (e.g., 9 L starter (2.3 gallons) for a 5 gallon batch where 4 vials are called for) in some cases. So, i've been trying to aim for proper pitching rates and, as such, doing starters. Obviously, spending 9-30 bucks on yeast is difficult to sustain so I need to know more about building starters. also, I'm trying to bank frozen yeast and am thinking about how to build those out. I have had good luck with yeast, building small starters, etc. but am interested in proper pitching rates and seeing for my own self how this changes my beer.

Click to expand...

I stepped a starter once doing 2L of 1.025 oxygenated wort, letting it ferment out, decanting, and then adding 2L of 1.040 fresh oxygenated wort. I had a PILE of yeast after that process, about 3/4" in the bottom of a growler. That was for a 1.090 tripel which attenuated at 1.014. I was aiming for 1.012 so I got pretty close.

Next time I'll just buy a gallon jug of apple juice and re-use the glass bottle for my starter. Doing two starters in one is just a lot more trouble than it is worth.