Thursday, April 22, 2010

Olive Oil and Homebrew

I've written about my willingness to violate the German purity law in making my homebrew, but I never thought I would go this far. I've started adding olive oil to my beer.

The issue is oxygen. Yeast need a certain amount of oxygen to do their work in converting sugary wort (the beer juice that you boil) into beer. The amount they need is a bit more than will wind up in the wort under normal brewing conditions, employing normal brewing techniques.

There are a few ways of getting more oxygen in the wort. One way is to shake the heck out of the carboy (the big bottle where you add the yeast and let it ferment) for a half hour or so. The downside of this method is that it's a lot of work to shake up a 50 pound bottle of beer, and I make ten gallon batches, so the work is doubled.

Another way is to bubble air through an aquarium pump and aeration stone (usually employing a filter in the tubing to get rid of floating wild yeast, bacteria, etc.). The problem with this is that you get a ton of foam, and it takes forever to add some air, wait for the foam to subside, add more air, and repeat until you bubble enough air through. Plus, the foam you create is composed of the same proteins and stuff you want to help your beer form head when you pour it, and, in a nutshell, when you use it you lose it. So you might wind up with a good, but flat beer.

The most professional way is to add straight oxygen to the wort, again, using an aeration stone. There's a little expense involved, and the stones are a bear to sanitize, but it's the best way to add oxygen. Sometimes, though, it can be too effective, and too much oxygen in the beer can make the yeast generate all kinds of off-flavors.

A little olive oil avoids the need for so much oxygen. I'm not biochemist, but much of the oxygen needed by the yeast goes to help form cell walls. Olive oil reduces the need for oxygen in this stage, because it provides the kind of fatty acids that the yeast would otherwise need to create by itself. The science is complex, but here's a 35 page thesis on the subject if you're interested.

To adapt the process to homebrewing, you want to use a minuscule amount of olive oil. Too much could conceivably affect the flavor profile, and way too much could destroy the head.

For a few recent batches, I've split my wort into two 5 gallon carboys, and added a tiny amount of olive oil to one of the carboys. I've straightened a paper clip, flamed the end, and dipped the tip into olive oil, then mixed it in with the wort as it runs from the boiling kettle into the carboy. The other carboy gets my normal method of oxygenation, which consists of a splashy trip into the carboy and a bit of shaking.

The results have been subtle. In a recent Vienna Lager, both versions had the same final gravity, but the one with olive oil tasted a bit smoother. In an amber ale, the difference was again subtle, but I preferred ever-so-slightly the olive oil version. (It wasn't a blind tasting, so it might reflect my bias in favor of a spiffy cheap way of improving my beer.) I've detected no downside to the method, and head retention is not impacted at all.

It sounds weird, but it seems to work. So, until I'm convinced otherwise, I'm bringing a bit of Italy to my homebrew.

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