The Trefethen Family Blog

By Zeke Neeley, Winemaker

Winemakers and coopers are often asked “what is the difference between French and American oak barrels?”  The simple answer is that they come from two different species of tree, but the real question is probably more accurately put “why would someone use French oak for one wine and American oak for another?”

First, a little history regarding oak barrels may be useful.  In the past, wine barrels have been made from many different types of wood including chestnut, acacia, and redwood.  Although I have seen the occasional acacia barrel, white oak has won out for two reasons: mechanical and aromatic.  White oak is easy to split, though I’ve never tried it myself, it can be bent and maintain a curved shape with good mechanical strength, and it doesn’t leak.  Oaks are generally quite porous which would lead you to assume that as soon as wine soaked into the wood it would pour out one of the stave ends.  What makes white oaks suitable for barrels is that its pores are blocked by woody plugs called tyloses.  Wine will soak into the barrel but rarely leak from it.  Aromatically, white oak is superior to other woods because, in spite of what critics may say, it is a relatively neutral wood.  I will, at times, complain about a wine being “over-oaked”, but I will take “over-oaked” wine over “over-pined” retsina any day!

The oak forests of France play a part in the history of France itself.  The main reason why France still has such extensive forests of white oak is due to a conscious effort of the French government almost 400 years ago to ensure that the French Navy had an ample supply of material for shipbuilding.  In the early 17^th century, the French government started the Bureau of Water and Forestry, which used ingenuity and a bit of arm-twisting to ensure that these forests lasted for centuries.  The amount of foresight needed is astonishing when you realize that the trees they planted in the 17^th century wouldn’t be useful for building ships (or barrels) for at least 200 years!  To increase quality, the Bureau instituted some clever strategies.  For example, for ship and barrel building, you want a tall straight trunk.  To achieve that goal, they planted chestnut trees around the oaks so that the oaks would have to grow tall to get sunlight.

American white oak, Quercus alba, had a bad reputation for years because winemakers were using used whiskey barrels which were heavily charred on the inside.  Now that American oak is being coopered similar to French oak, we have seen some interesting differences between the two.  In general, French oak releases more tannins, phenols and solids in into a given wine.  This adds to what people call the “structure” of a wine—the tactile sensations of body and astringency.  American oak will release compounds like oak lactones and vanillin at a much higher rate than French oak.  These are responsible for some of the “oaky” flavors that you get in a wine like vanilla, clove and coconut.

Because of the stronger flavoring, many feel that more delicate wines like Chardonnay and Pinot noir are overwhelmed by American oak.  It is generally more accepted for use in robust Cabernets or Zinfandels.  I have nothing against American oak, but in my opinion it is the wrong choice for Chardonnay.  When we at Trefethen Vineyards barrel ferment Chardonnay, we are looking for flavor and structural contributions from the barrel.  In my experience, Chardonnay aged in American oak is often disjointed—it has more oak flavor than we want before it has gained the desired structure.  To get the desired structure, we would have to leave the wine in barrel longer, with the very real risk of the flavors and aromas of the oak overwhelming the fruit.

That said, scientific studies (yes, scientists study oak barrels) have shown wide variation between individual barrels that confounds broad generalizations about American vs. French oak barrels.  Some highlights that confuse the situation:

• The variation between barrels made from trees from the same forest is often greater than the variation between barrels made from different species of tree.
• The amount of extractable flavors and tannins varies within the same tree depending on how far up the trunk the stave is taken.
• The width of the grain in the wood is a determining factor on how quickly flavors are extracted into the wine.
• After splitting, the staves are left in stacks to dry in the open air for two or three years to “season.”  The climate in which the wood is seasoned impacts the future flavor of the wood—you can imagine that the climate and microflora of Bordeaux would be different than that of Missouri, both locations where cooperages source their lumber.
• I haven’t even touched upon the different methods of building and toasting a barrel that cooperages practice.
  • Does the cooperage bend the staves in water or with dry heat?
  • Do they perform a fast and hot toasting or slow, warm one?
  • Do they toast with the barrel head in place or absent?

So, perhaps the best course of action for winemakers is the route we take at Trefethen.  We experiment with our barrels.  We can make an educated guess which barrels will work best with our different wines, but there is no substitute for tasting.  We may put a given lot of Cabernet sauvignon into barrels from up to six different coopers then taste them over the next year.  We find that our Petit Verdot can stand up to a barrel that would overwhelm our Merlot.  Our Chardonnay and Pinot Noir require fewer new barrels—offering only a subtle touch of oak—than our Cabernet Sauvignon, which is complemented by the spiciness and structure of new French oak.

We experiment with a couple new coopers every year and maintain a dialogue with our current coopers.  We let them know which barrels worked best the previous vintage and ask these expert craftsmen to replicate their magic every year.  Come to think of it, that sounds a little like winemaking.

Cheers,

Zeke