German Brewing

I'd buy it.

Has anyone taken the time to watch this video? It's pretty informative on pitching volumes and oxygen. I prefer (generally) to underpitch slightly (which is typically one package) to get the most character out of the yeast. Oxygen ppm is always needed. Regardless, listen to this very well spoken video. Cheers!

SteVe

It has been my experience that even with larger pitches, a little oxygen helps the yeast get rolling faster. I don't add very much - I just have an air stone connected to an aquarium pump that I dangle in the wort, and after pitching the yeast I let the pump run slowly (not anywhere close to fast enough to create foaming) for several hours.

I've measured that I deliver about 2 ppm per hour this way, and the yeast are capable of eating up that oxygen at a faster rate than it's getting in.

In theory, repitched yeast is oxygen depleted and requires oxygen to rebuild its cell walls. There's also a finite lifespan that each cell has, so past a certain point they won't be able to bud or ferment well. Kunze and Narziss both suggest mixing harvested yeast with freshly grown lab yeast and pitching that. I've had good results by taking a scoop of the yeast cake and using it to inoculate a starter, fermenting it out, decanting and pitching that. I'll typically make a 2-2.5 liter starter for my 13 liter batches. A starter should be very well oxygenated to help the yeast grow big and fat and ready to ferment your wort. One effective method is to use a stir plate on a slow speed (just enough to get the wort moving) for the first 8-12 hours, as this will accelerate atmospheric diffusion of oxygen into the wort and provide a constant stream of oxygen during the growth phase. You can take the starter off the plate once the yeast start of gassing. Most of the time though, I don't use my stir plate and I just give the stater a vigorous shake every time I walk by.

I have such a small batch size (1-1.5 gal) and a single smack pack will typically ferment even my highest gravity beer, so in that regard I've always lucked out by not having to do starters.




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I've tried the no-oxygen batch of beer, and it took a few days longer to reach EVG than batches where I oxygenated. I'm not sure there was enough flavor difference to be noticeable. I need to experiment with the Rabe pitching method, but I've been playing around with other variables and styles as of lately.

I like to take 50% of the cells I need from the cake of a previous batch and pitch it into a new starter. That way, under aerobic conditions, the cells will get healthy and as they reproduce, all of the new cells will be grown in an oxygen rich environment. You've effectively created a batch every bit as healthy as a series of built up starters, but cut your work in half. Since 50% of the cells are brand new and grown aerobically, in theory, the pitch will never have to be replaced and can be continued indefinitely. Straight cake pitching has a limited lifetime. Additionally, since we are separating the more flocculant cells from the less flocculant cells because of the transfer to spunden, we are selecting for a less attenuative yeast cake over time.

There are some conflicting theories on stir plates as well. Kai showed higher cell growth with faster speeds, but Annemüller demonstrates decreasing cell vitality with increased shear stress. Just more variables to test