That is a very good document and your results speak for themselves. However, I would like to discuss something that is covered in the document under the “Quality Control” section.
As I have mentioned many times and covered in great deal in my blog entry entitled “Yeast Cultures are Like Nuclear Weapons” (Yeast Cultures are Like Nuclear Weapons | Experimental Brewing), pitching rates are more about out-competing competitors than anything else. Granted, in high gravity beer, we have the double whammy of lower O2 absorption and higher osmotic pressure that requires us to pitch higher cell counts due to the increased difficulty of growing biomass combined with increased premature cell death due to high osmotic pressure, but most fermentations are not high-gravity fermentations. A pitching rate of 50G/hl equates to a per gallon pitching rate of 50 / 26.4 (gallons in hecto liter) = 1.89 grams. For the typical 5.5 gallon starting wort volume, that equates 5.5 * 1.89 = 10.4 grams, which is why the dry sachet size is 11 grams (the metric equivalent of the 5-gallon batch is 24 liters, which is 6.3 U.S. gallons, so 11 grams is still good enough). When pitched at this rate, what prevents a fermentation from fully attenuating is a combination of strain genetics, wort composition, and dissolved O2 demand. Let’s face it, a lot of amateur brewers are aeration challenged. In poorly aerated wort, it is not the pitching rate that controls fermentation, it is a yeast strain’s genetically programmed O2 demand. I have previously covered Brian Kirsop’s work on O2 demands from his seminal paper on the subject entitled “OXYGEN IN BREWERY FERMENTATION” (https://onlinelibrary.wiley.com/doi/epdf/10.1002/j.2050-0416.1974.tb03614.x), but here are the O2 classes from that paper again:
Class O1 - yeasts whose oxygen requirement is satisfied if wort is half saturated with air
Class O2 - yeasts whose oxygen requirement is satisfied if wort is saturated with air
Class O3 - yeasts whose oxygen requirement is satisfied by oxygen-saturated wort
Class O4 - yeasts whose oxygen requirement is not satisfied by oxygen-saturated wort
That being said, I believe that the most popular yeast strains in amateur brewing fall into the O1, O2 O2 demand range, which means that most have O2 demands that can be met by saturation with air. For example, below is the strain information for NCYC 1026, which is the Whitbread B strain. We know this strain as Wyeast 1098, White Labs WLP007, and Fermentis S-04. We see that the strain has an O2 demand of O2. We also see that it has above taste threshold lactic acid production, which is why beers that have been fermented with it have a tart edge. What most brewers do not understand, it that this yeast strain did not make its mark in brewing in batch-based fermentation. While the strain was deposited in 1958, it made its mark in the mid-sixties with A.P.V. continuous tower fermentation vessels, which are basically bioreactors designed for continuous beer production. I suspect that the reason why this yeast strain does so well when propagated in a bioreactor is because it did so well in A.P.V. continuous tower fermentation, which means that it probably comes out a bioreactor with enough ergosterol and unsaturated fatty acid (UFA) stores that it is almost insensitive to wort dissolved O2 level.
NCYC 1026
Information
Flocculent
NewFlo type flocculation.
1:5:4:5:5
O2, DMS 33 µg/l, low acetic, high lactic (which is why the strain produces slightly tart beers),
diacetyl 0.42ppm only, used commercially in Tower Fermenters (continuous process),
non head-forming, no estery flavour. Contains 2µ plasmid.
Depositor
British Brewery
Deposit Name
Saccharomyces cerevisiae
Month of deposit
June
Deposit Year
1958
Habitat
Ale production strain.
Continuing, most of us have experienced long fermentation onset times with BRY-97. Is that because we underpitched? Or is it because we did not bother to aerate the wort? Could it be that the long delay in the onset of active fermentation is the result of BRY-97s inability to come out of bioreactor-based propagation with fully-charged ergosterol and UFA reserves? Or is it that the strain suffers high cell death in the drying process? Could it be that the isolate has higher O2 demands than its parent BRY-96? Or are we just spoiled by isolates of BRY-96 that work faster than the original? On the Siebel spreadsheet that I received from Lallemand, BRY-96 is labeled as having a fermentation progress of “slow.” How many people consider Wyeast 1056, White Labs WLP001, or US-05 to be slower performing than other cultures? Finally, why does BRY-97 act normally when it is repitched? Is it because we are pitching a much higher number of cells? Or is it because we are aerating the wort? Granted, higher pitching rates do reduce the need for aeration, at least, for one serial re-pitch. Maybe, I will get around to running an experiment where I highly aerate wort before pitching a single pack of BRY-97.
