Lots of wine lovers talk about wood, but what does it all mean?

The subject of wood gets bandied about so often that sometimes I feel I should carry around a hammer and nails. How does wood get to be so commonly thought of as an integral part of wine-making and drinking?

In the bad old days, there were a couple of materials used for wine making, storage and transport. Probably the most common was the amphora, a container made of some type of clay and used for fermentation and storage, often buried in the ground for ageing.

The oldest use of wood barrels is mentioned in the Oxford Companion to Wine as dating back to seven centuries B.C. Nowadays, fermentation casks can be made of stainless steel, epoxy, lined concrete and wood. Red wines are often aged in oak barrels, generally of American or French origin.

Why oak? Why French or American? Should staves be split by hand or machine cut? Should the staves be air or kiln-dried?

Oak is tight-grained and does not leak when a barrel is well made. Quercus alba is white oak, whether French or American, but they differ. American is tighter grained and is stronger because of the way the wood grows. French oak requires hand splitting because lateral channels that strengthen American oak are not as predominant in French oak.

What the wine gains (or not) from oak are aroma (lactones), flavor (phenolic aldehydes, vanillin, for example), spice (volatile phenolics—think cloves, allspice), tannins (color, astringency, prevent oxidation). In a barrel, yeast is active as the wood allows air in and the yeast interacts with chemicals leached from the wood to transform them into other chemicals that we come to recognize, in part, as a wine’s complexity.

Toasting a wine barrel creates a series of complex reactions. Wood sugars produce a bitter almond flavor when toasted as well as aromas and flavors of caramel. Toasting the wood creates a group of chemicals known as flavor potentiators, i.e. substances that encourage or allow the formation of other flavors. They work in much the same way as MSG does with food in that the perception of the flavors is increased when these chemicals are present.

When barrels are used for long periods of time, much of their flavor characteristics become neutralized. Barrels of more than four vintages are typically sold off to distillers or used for producers who look for more neutral barrels for their storage, preferring old wood to stainless steel.

White wine barrels in Alsace become lined with tartrate crystals from wine storage to such a degree that they need to be scraped and chiseled out to have adequate storage volume. Some Alsatian casks are more than a century old and vintners use them because they feel they are able to retain the purity of fruit while still mellowing the wines. That may seem a paradox, but wine-wood interaction is a complex process.

It is a complex situation and must be studied by continuous sampling of delicious wines in order for the erudite consumer to be well versed in the subject!

Cheers.

Harry Haff, a.k.a. Wine with a Chef, teaches Wines and Beverages at Le Cordon Bleu Atlanta. He is a two-time Certified Chef and holds and an Advanced Certificate from the WSET in London. Contact him at winewithachef@mac.comThis e-mail address is being protected from spambots. You need JavaScript enabled to view it.