Barrel Derived Aromas and Flavors

Question from Paul: Someone told me that if wine smells like vanilla it comes from the barrel. Is that right? It doesn’t make sense to me.

Reply: Hi, Paul. Thanks for writing! Yup, it’s likely that it comes from the barrel although we can never be absolutely certain. Vanilla is a plant and grapes are plants so there’s always the chance that they share some flavor compounds but vanilla is very high up on the hit parade of barrel derived characteristics – There’s vanillin in oak.

The barrel is second, only, to the fresh grapes when it comes to flavor impact on the wine. It has three important impacts:

1. The slow aeration that occurs matures the wine away from simple, primary fruit characteristics adding complexity as it softens the wine and marries fractious components into something more cohesive.

2. Evaporation concentrates the wine a bit, adding to its weight.

3. If the barrel is relatively new, it imparts lots for different aromas and flavors such as vanilla, coconut, baking spices (especially nutmeg) smoke, coffee… the list goes on and on.  Barrels are like tea bags in that they give up their flavor with age. Some winemakers prefer older barrels that don’t impart flavor to the wine.

The most important factors are:

  • The species
  • Tightness of the grain (influences how quickly flavor and tannins are imparted)
  • Location of the forest
  • How long it’s seasoned (air dried)
  • The toasting level – how hot the fire and how long it stays on the fire.
  • The size! The larger the container, the slower the oxidation and the less wine-to-wood contact. That can offer an advantage when aging white wine in particular.
  • Whether or not its been used before.

That’s a lot of variables!  Let’s take on some of the most important ones. 
American vs. French oak:  The most common difference in species is American (quercus Alba) vs. French oak (quercus sessilis or q. robur), so here’s the broad-brush differentiation: It’s generally acknowledged that American oak contributes tannins slowly, but its aroma/flavor quickly, so it’s easily overdone. French oak is slower to influence aroma and flavor, but quick to impart tannins so it may contribute more structure. Blending the two within one barrel is not unheard of.

The toasting level: A major influence on the flavor characteristics. The traditionally-made oak barrel is bent into place over a fire made of oak scraps. After bending, the barrel is toasted and the most common designations are “light”, “medium” and “heavy” toast which corresponds to the length of time the barrel is toasted and how long it spends at the maximum toasting temperature. As you go from light to heavy toast, of course, the barrel is darker and darker on the inside.

  • Light toast:  Will usually give you the most true oak flavor, some coconut and vanilla and subtle baking spices
  • Medium toast: Decreases the woody flavor, brings up the vanilla, adds more baking spices and toasted bread
  • Heavy toast:  Less vanilla, more spice, smoke, coffee, mocha; the wood sugars are caramelized and it may give the nose a sense of sweetness

None of this is hard and fast because of the other factors in involved, but you can see the trend away from woody flavors to dark, sweet influences as the inside of the barrel gets darker. The winemaker usually chooses a selection of barrels for one batch: new, flavorful barrels and older, neutral ones; some lightly toasted, some dark, etc. He blends these lots together to come up with the final blend.

I hope that helps! Cheers!


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