Let Your Beer Breathe!
Back in the summer, I had the chance to make it down to Holy Waters (huge thanks to Paradise Grapevine and Escarpment Labs). Rob and I split our days: he went to the beer day and I went to the Wine Symposium. There are a lot of aspects of the new (read: very, very old) traditions of natural wine making that mirror how we make our beer. Natural wine makers treat their fermentations the same way lambic producers do, relying on the yeast and bacteria in the environment and on the skins of the grapes for fermentation. But, it was one of the differences that I found the most interesting.
When it comes to beer, oxygen is bad. It will turn your toasty malt flavours to cardboard, and your hop aromas to… nothing. But, when you talk to winemakers, they’ll tell you that oxygen is an important ingredient, crucial to the development of wine. In the book Postmodern Winemaking, there are multiple chapters dedicated to the artful proper application of micro-oxygenation (MOx). It’s common for entire styles to be at least partially defined by their “reductive” or “oxidative” characteristics (recommended reading). How much the winemaker allows or doesn’t allow oxygen to take part in the aging process is just as important as the type of grape, or choice of wood for a barrel in making a wine what it can be.
Can we also use oxygen as an ingredient in beer making? Of course. High oxygen rates before and during fermentation allow for increased and healthier yeast growth and result in much lower ester production. Want an extra-crisp, refreshing IPA where the hops pop? Consider aerating your wort a little more than usual. Want to make a Hefeweizen with even more of that banana character? Make a wort with more simple sugars and ferment a little warmer, two variables that can also vary ester production. We don’t recommend sacrificing yeast health by underaerating your wort. Healthy yeast will always make for a better beer.
When it comes to funky beers with Brettanomyces, however, this gets flipped on its head. Brett can take esters and, through combination with lactic, acetic and isovaleric acids (which are commonly found in sour beer), turn them into new esters. Ferulic acid, which in Hefeweizens becomes 4-vinyl-guaiacol, can instead be turned into Ethyl Ferulate, which is more of a spicy, cinnamon flavour. There’s a huge list of what can be made, so I’ll just add a list at the bottom. The important thing to note, though, is that its been shown that the parts of Brett that make this happen are at their most active in the presence of a limited amount of oxygen. This is why aging in barrels is magical. A small amount of oxygen can give the yeast what it needs to make these new, exciting flavours.
The key here, though, is that oxygen is good for aging beers in small amounts. If you leave your carboys open, it will turn into vinegar ten times out of ten. But, if you think about adding oxygen like any other ingredient, carefully and thoughtfully, you could unlock a whole new world of funk!
Diagram Source: http://sourbeerblog.com/understanding-esterification/ *Recommended Read
MORE RECOMMENDED READS:http://www.milkthefunk.com/wiki/Brettanomyces#Ester_Production