This is one of those posts that I put out there not only to educate but to get some discussion going around one of the most interesting but often misunderstood aspects of winemaking. I think when most people in vision a winery oak barrels almost always show up in their mind’s eye.
First off there are two main types of oak that are used in winemaking; French and American. The species of French oak can be from Quercus robur or Quercus petraea and American oak is typically Quercus alba. Both have pros and cons and typically the choice comes down to winemaker preference and desired style.
The French Oak species grow more slowly than their American cousin which makes the rings in the trunk appear more closely together. This gives the staves made from this species a tighter grain. Why does this matter? The tighter grain gives the oak different flavors from it’s wider grained cousin. It also encourages the addition of extra oak tannins. The flavors given off by the wood depends on the toast level.
American Oak Toast Profiles:
Light Toast/Medium Toasts = Coconut, Vanilla, Brown Sugar, and Cinnamon
Medium +/ Heavy Toasts = Toasted Marshmallow, Caramel, and Cloves bordering on coffee
French Oak Toast Profiles:
Light Toast/Medium Toasts = Vanilla, Cinnamon, Nutmeg (all manner of brown spices really), and Cedar
Medium +/ Heavy Toasts = Roasted Coffee, Tobacco, Smoke, and Charcoal
Once a winemaker has decided what oak to use and what toast level all that is left is to decide what form the oak will take.
Barrels are the traditional choice. They can be formed several ways including through fire, steam, or water then toasted using heat, usually from an open flame. They allow the wood to integrate into the wine consistently while softening the wine through the occasional introduction of oxygen throughout the topping process. The wood itself does not transmit very much oxygen once it becomes saturated with wine and tartrate crystals. They are convenient fermentation vessels for white wines as the small amount of volume per barrel does not heat up rapidly and can be easily controlled by placing the barrel in a temperature controlled room or cave. Barrels are also ideal for small lots of wine if a tank is not an ideal size. There are some downsides however including the fact that once a lot is split up into barrels there are numerous 59 gallon lots that all begin to react and age differently. It also takes a large amount of time to maintain empty barrels and wine lots stored in barrels including frequent analysis and topping to prevent oxidation and spoilage. Personally, there is nothing better than the fresh smell of new oak barrels and the excitement of tasting through barrel lots to blend wines.
Similar in shape to the staves that will eventually become barrels, oak staves are long segments of oak that are individually toasted without the bending process. The staves I’ve seen are usually thinner than the barrel staves but depending on the producer they are toasted in much the same way as barrels or they can roasted in a convection oven. Again, like barrels, the toasting method very much depends on winemaker preference and each way does tend to produce different flavors. The flavors and quality of staves varies widely from stave producer to producer. Poor quality staves tend to have the flavors sit very intensely on the nose of the finished wine but lack follow through on the palate. Good quality staves, when applied properly, can integrate very well and can be difficult to tell apart from barrels.
This section of oak runs by many names. They are smaller than staves but usually larger than dust. They can be cut up staves, beans, cubes, chips or spirals and they usually come packaged in an infusion bag similar to that of tea (only larger of course). These are great for quick infusions of oak but when used too liberally can have the same problem as staves where the oak sits on the wine but never integrates. They can be useful for reviving older barrels but can be difficult to work around if lees stirring is part of your winemaking style. Like most things, a little bit goes a long way!
Before you get the idea that winemakers are throwing hamster shavings into wine know this; Oak dust can be your friend! It’s super helpful in covering up herbal flavors in red fermentations as well as adding some quick tannins to attach to color molecules in the new wine. It is not normally used for adding oak flavor but gently supports the fruit’s already developed attributes. Don’t worry, most of it gets pressed off with the skins and the rest disappears by the first rack. It’s only present a very small amount of time but it can make a huge difference in structure for younger wines.
That’s it for the quick Quercus 101. Its the most interesting exercise to taste through wines trying to determine French or American, Barrels or Staves, Light or Heavy toast? I highly recommend it. The results might surprise you!