Splish Splash

Got an email from a reader with a question about aeration and yeast. Any further reader input would be welcome…

Hey Scott,
Just found your blog,  while searching for the origins of the dark IPA.  I’m going to attribute it  to Greg Noonan just like every Vermonter should.  I’ve been trying to get  better with homebrewing and have been a little concerned with aeration of the  wort going into primary.  I’m a PhD student in biobehavioral neuroscience  so I get a bit anal about things, bear with me.  As a scientist I want a  specific value for dissolved oxygen necessary for a good fermentation, I find  that nowhere.  Some suggest a vigorous shaking of the wort, I’ve read of  aeration systems (access to medical 95%02, 5%CO2 so I’m tempted), and I’ve also  read many that like you suggested transferring the wort so that it is a bit  splashy and aerates “enough” (the scariest option for me as a scientist, I need  control!).  Is a good pour typically enough to provide enough oxygen for a  healthy ferment?

Enjoying the reading material you provide.  Thanks!
Brendan

Hey Brendan, thanks for checking out the blog! Glad you’re enjoying it.

As you probably can figure out from my posts, I am NOT much of a scientist – I have no idea what kind of dissolved oxygen ratio would be ideal for optimum start-up. I have, for my entire brewing career (20 years) observed that pouring the wort into the fermenter and allowing it to splash well has been more than adequate. For a short while I used a counterflow wort chiller, siphoning the wort through copper into the bucket, and I am absolutely certain that there was not enough aeration occurring then – I had several batches that took days to start, and ultimately had off-flavors that one would associate with lag spoilage bacteria… Using the “pour and splash method” I usually get active fermentation within 4 – 6 hours, even quicker if I have built up a starter slurry…I don’t have my copy handy right now but I’d bet if anyone has quantified the oxygen content question it would be found in Greg’s “New Brewing Lager Beers“…
best of luck,
Scott

3 Replies to “Splish Splash”

  1. I agree with Scott, in that splashing the wort provides quite acceptable results. I switched to oxygen more for the geek factor than to address any real fermentation problems. According to the excellent book Yeast, by White and Zainasheff, the proper amount of dissolved oxygen is about 8 to 10 parts per million. Splashing the wort will result in at best 4 parts per million. In fact, shaking the carboy for 5 minutes will provide 2.71 parts per million in a wort of 1.070 gravity. Using an aquarium pump and a sintered (aeration) stone will never result in more than 8 parts per million. For 10 parts per million, use pure oxygen through a .5 micron stone for 60 seconds per 5 gallons at 75 degrees. Higher gravity worts generally require more yeast, and therefore require more oxygen. The 8-10 parts per million rule should be fine for worts of 1.070 or lower gravity. You can get a small disposable oxygen tank from any welding section of a hardware/home improvement store, and homebrew shops sell the complementary O2 Oxygenation Kit for about $40. Hope this helps!

    1. This is why I threw the question out there – thanks for the info, Phil. I second your recommendation on White & Zainasheff, although it is a quite complicated book for us non-scientists. I’m going to start selling T-shirts that say “Everything I know about Microbiology (sub in Chemistry, Thermodynamics, etc…) I learned from Home Brewing”…

  2. I’m also a science-minded homebrewer (I’m a chemist by trade), and I generally find that background to be highly useful in my brewing exploits. However, sometimes it can be easy to over-analyze things a bit. This is one of those instances where it might be appropriate to consider that brewing is also an art and that it has been practiced for thousands of years, mostly by folks who knew next to nothing about science in general or oxygenation in particular. A certain level of intuition and the challenging of one’s science-based comfort zones is necessary at times, else you can end up running yourself in circles and not getting any sleep at night. An example from personal experience: when I first started kegging my brew I got a bit anxious over the lack of a sub-micron filter on the CO2 inlet. (How clean is that gas, anyway?!) Eventually I decided not to fret over it, it must not be a significant risk of contamination since that’s how it is typically done, and indeed everything has been fine. Certainly I do geek out over some things, such as recipe development, optimizing mash conditions for maximum extract efficiency, etc. But overall I’ve found brewing to be a bit more fun when I can let myself relax, take some risks, and not let myself get too wound up.

    So my advice, the short/practical/on-topic version: try splashing. If you are encountering issues with slow starts or poor attenuation, then maybe give it some more thought. I put my wort through a large funnel that has a plastic mesh filter insert, and this seems to put quite a bit of air into it. Also, the cooler your wort is the more oxygen it will hold… so if your wort is still at all warm (significantly > room temp), try chilling it further. Good luck!

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