Oak barrels have been used in brewery storage for many years, but recently craft brewers have turned to oak for its aroma, flavor and mouthfeel impact. Commercial craft brewers are likely to use barrels, often ones that were previously used for whiskey storage. Barrel-storage between batches and batch sizes are a problem for homebrewers, so we are more likely to follow in the steps of Budweiser and use wood chips or cubes; except for a few who use dowels or chair legs. Homebrewers will also be likely to use oak instead of Bud beech.
"Grown in America, Beechwood is harvested and processed into chips for use in Budweiser's fermenting process. Beechwood aging enhances fermentation creating a crisper, more sparkling carbonation while imparting smoothness..."—The Budweiser Way, http://www.budweiser.com/
When used effectively, oak-aging can enhance beer flavor and complexity lending the full, rich properties of the wood. When overused, oak can make your beer too dry and "woody." All of this is dependent on the specifics of how you do the aging. There are several basic flavors that derive the the compounds found in all species of oak:
- Eugenol: Clove-like taste
- Furfural: Caramel sweetness
- Lactones: Coconut and aromatic wood flavors
- Vanillin: Vanilla aroma and flavor
The three most common types of oak used by brewers are American, French and Hungarian, and each has its own flavors. Each is available with different levels of toast, typically Light, Medium, Medium+ and Heavy. The flavor profile of oak changes during the toasting process, so the flavor and aroma compounds that come out depend on the variety of oak and the level of toast it gets.
Chips vs. Cubes: Chips are generally thin, flat shreds of wood similar to the chips of wood you get when chopping a tree by hand with an ax. Because of the thinness of chips, the toast level is more uniform and they impart their flavor to beer fairly quickly. (Speed is the attraction to beech chips for the folks at Budweiser who appear to pare theirs down to ribbons of wood.) Due to their relatively greater thickness, cubes may be able replicate the complex flavors of a barrel a bit better than chips because the cubes have more levels of toast. Cubes also expose un-toasted surfaces to your beer, something that doesn't happen in barrels. Cubes take a bit longer to impart their flavor and cost more due to being more expensive to produce. Which is better? It depends on your usage.
Sanitation: Maintaining sanitation is a concern, but it's not as big a problem as sanitizing barrels. There are multiple ways to go, and have used several successfully:
- Steam: Put your oak cubes or chips and 1/4 cup of water into a microwave-safe container with a loose-fitting lid. Microwave on high for three minutes. Let it stand for another three minutes.
- Boiling: Use just enough water to cover the wood, and cover the pot or container with a loose-fitting lid. You can do this on the stove top or in the microwave.
- Alcohol: There are some sanitizing properties in alcohol, and the level of alcohol in whiskey is enough to do the job with prolonged contact. I use a Mason Jar and just enough booze to just cover the wood. You'll need to add more booze almost daily as the oak absorbs it.
- Oven: This method should work just fine but I haven't tried it so I have no recommendation on heat or times.
- Pressure Cooker: The super-safe way of steaming. Very effective but requires extra equipment that most homebrewers probably don't have.
- Just throw them in: You'll probably be just fine in most cases.
Process: There are several ways you can oak your beer:
- Chips/Cubes in the Primary: Put your oak cubes or chips in when at the same time you add your yeast The yeast will metabolize some of the oak vanilla flavors and leave others behind. Chips are probably the better option here due to short duration.
- Chips/Cubes in the Secondary: This is probably the most common way for homebrewers to do oak aging.
- Oak Tea in the Secondary: If you sanitized by boiling or soaking in alcohol you now have an oak tea of one sort or another. The alcohol-based tea will be laced with vanilla. The water-based tea will be dry, woody and possibly a bit astringent if you've boiled it for long.
- Hybrid: Some combination of the previous methods.
I've had success creating bourbon-aged oak flavor by soaking the wood in bourbon for several weeks. You could add only the chips to your beer after a shorter soak in bourbon, but with several weeks to work, the bourbon gets gradually darker as it pulls the flavors and toast out of the chips. If you add only the chips and discard the bourbon tea at this point you're probably throwing the baby out with the bathwater. If you add only the tea and discard the chips you're probably doing the same thing to a lesser degree. Reserve the tea until the end of your aging process and add it in gradually until the taste is right. Switching to Port for a Port Barrel Aged Old Ale also worked well.
Depending on the quantity and variety of oak you use, the taste of your beer will change more or less subtly over time. You'll probably need to wait at least a couple of weeks and maybe as much as six months. You'll need to taste the beer during the next weeks/months to monitor how the flavors of the oak compounds are mergiong into the flavor of your beer.
The Brewing Network has
a good discussion of wood aging but it takes a long time to download. Not because of file size, their sever seems to have issues.
