ox·i·da·tion – /ˌäksəˈdāSH(ə)n/ – noun
Beer is good stuff, right gang? However, as we’ve seen in previous Vocabrewlary Lessons (diacetyl anyone?), sometimes bad things happen to good beers. Accidents happen. Careless mistakes occur. Much like the dreaded missing sock, sometimes beers get lost in the back of the fridge only to turn up when your picky cousin Don comes over and goes foraging through your Kenmore. When these things take place, you’re likely to get some off-flavors and the one we’re talking about today is oxidation.
Per the usual, my typical disclaimer about the fact that this is a general overview of the topic mentioned above and not an in-depth science lesson applies.
When you introduce oxygen to stuff and that stuff changes chemically, that’s oxidation. That stuff has been oxidized. Since this is a beer blog, it’s safe to assume that the “stuff” we’re talking about is beer. It’s also important to know that “oxidation” and “infection” are not synonymous so don’t go interchanging the two, por favor.
Beer can become oxidized in a handful of ways but let’s look at the most common causes:
- The Brewing of Beer – This type of oxidation is called “hot side aeration.” Oxygen is introduced during the mash, lauter, boil or whirlpool. This is the least common way oxidation occurs by far but it can happen. Splashing around the wort during these processes is the main culprit so if you’re brewing on a big scale or a small scale…don’t do that.
- The Packaging of Beer – This is part of the classification of “cold side aeration” since it’s after the hot brewing process. When you fill bottles or cans with beer, you need to purge the bottle or can of oxygen by blasting some carbon dioxide into the empty vessel first. Bottles and cans aren’t just filled to the top for maximum goodness, it’s also to eliminate that extra oxygen in the headspace.
- The Storing of Beer – This is by far the most common way beer becomes oxidized. When beer is past its “drink by” date it can become oxidized. If it’s stored too warm for a long period of time (sitting out in your garage and cooling one bottle at a time as needed like some kind of monster) or at a very high temperature for shorter periods (in your trunk over a summer weekend), it can become oxidized. Bottle caps themselves aren’t perfect and will eventually allow oxygen in, too.
The fun part about oxidation is that it shows up as a lot of different flavors. There are a few chemicals that the flavor comes from but the main culprit is called trans-2-nonenal and tastes like wet cardboard, paper, wax and lipstick. The other big oxidation compound is 2, 3 Pentanedione, which brings a honey-like character to affected beers (not in a good way). So unless you have a fantasy about making out with a lady bee teacher as she grades papers in the rain, oxidation won’t make your beer taste better.
As always, there are some exceptions to the rule when it comes to the flavor of oxidation. Due to some extra special chemical stuff that takes place, oxidation in some beers can produce sherry-like flavors (mostly in dark beers) that can actually add to its flavor in a positive way. If you didn’t know already, beers over 8% ABV, if properly stored, can be aged for years before drinking them. Dark beers are more commonly stored for this purpose. The higher alcohol percentage of these “cellared” beers preserves them better than lower ABV brews and if the oxidation is subtle enough, it can bring some great vinous qualities to the table.
If you’ve read this far and are dying to know what oxidation really tastes like, pop the top on your favorite light lager, wait a couple hours, then pour it into a glass. The first sip should give you what you’re looking for.
So the next time you take a drink of that St. Louis Rams can of Bud Light you found behind the ketchup, you’ll know exactly what caused you to spit-take and why. You’re now able to amuse your friends and impress potential suitors with this life-changing knowledge. Let’s just all agree that if that bee thing I mentioned up above hits a little too close to home, there’s no reason to talk about it again, okay?
Do you have a beer term that you’d like to know more about? Email me at firstname.lastname@example.org or comment below with something you’d like to see explained in a future Vocabrewlary Lesson.