I’ve been utilizing drauflassen (basically pitching an appropriate amount of yeast for a specific volume of beer and then adding an equal or greater volume of beer on top of that inoculated batch after 12-24 hours after the yeast has basically doubled or tripled it’s volume) very successfully with no flaws that can be detected by sensory observation. Which is great because it allows me to buy a smaller pitch of yeast for a larger volume of beer.
Thing is, I have only ever done this on lower gravity beers, not higher gravity. I was wondering if anyone out there (specifically our resident yeast expert, s. cerevisiae) had any opinions on any negative outcomes that could result from high gravity practicing of draufassen. I’ve not gone higher than 1.065.
My first thought is that if you have the ability to do so, then brew the initial batch at a lower gravity and step up the gravity on the second half.
I’ve heard of this technique before, and in practice it really sounds no different than pitching a starter at high krausen. I’m surprised that more breweries that brew double or triple batches to fill their fermenters don’t use this technique.
Steven Deeds in his book Brewing Engineering discusses this technique. A really great book that gave me new insight on yeast management that I coupled with s. cerevisiae superb suggestions. I brew only big beers >1.080 and have entirely changed my technique due to these two gentlemen. I am now able to ferment these big beer quite dry with no stalls.
I start with low volume step propagation. I use this technique with frozen vials of yeast I made kept in the freezer. Pitch yeast into one liter 1.035, chill - decant and into one liter 1.070, chill - decant and into a calculated volume of wort around one gallon. Let that ferment 24 hours then pitch the remainder of the wort, about 11 gallons on top of that.
I no longer make these huge volume starters with this technique. Simply using a portion of the wort produced on brew day as the big volume starter.
A lot of commercial breweries do. But I’m not sure if any do it with high gravity pitches. Thus far I have always harvested yeast from lower gravity beers for higher gravity beers.
The Bigfoot time lapse has a couple of rises, the first is a fill and O2 and yeast added, the second is more wort on top IIRC. Might have to see if I can ask the sequence from a SN contact. They might also add more yeast with the top up, as they have several rows of yeast propagators at the brewery.
They also have some round open fermenters like you see in the German Wheat beer breweries in Mills River.
The initial pitch should weed out the cells that cannot handle the osmotic pressure, leaving the fittest cells to replicate. The number of cells that are available when the second wort addition is added is much higher than the initial pitch, and the combined gravity should be lower than the wort O.G. As the process calls for adding aerated wort, the cells that are in suspension will be able to replenish their ergosterol and UFA reserves before tackling the larger volume of wort. It’s basically a large high-gravity stepped starter.
