Craig Suveg on Oak Barrels, Their Flavors, and Their Place in Winemaking

By President Craig Suveg

While working in the tasting room, I receive many different questions concerning wine making techniques and procedures. One often asked question involves my use of oak. The use of oak for aging  wine has always been of interest to me so I decided to share some of my thoughts on the subject.

Oak barrels simply represent a storage vessel for aging wine; the general purpose being the gradual introduction of oxygen into the wine in order to stabilize color, vary the flavor and tannin profile and define the wine’s texture. The exposure of the wine to oak creates different flavor profiles depending on several factors including the species of oak, the capacity of the barrel, toast levels (wine barrels are toasted while whisky barrels are charred!) and percentage of aging time in neutral versus new barrels. Depending on the intensity and exposure to heat, toasting of the barrels breaks the chemical bands of wood sugars including cellulose and hemi-cellulose after which tannins are broken down in order to emit ellagic and gallic acids, which are part of the polyphenolic family tree of tannins. Generally speaking, flavor profiles can be characterized in five categories:

1 Eugenols – cinnamon, clove and spice;

2 Furferols – carmel, butterscotch;

3 Guaiacols – smoke, charcoal

4 Vanillin – vanilla;

5 Lactones – coconut, toast

In 2010, we began winery operations using exclusively Hungarian oak. All wine produced was aged in a combination of Quercus patraea and Quecus robur 114 liter and 225 liter new Hungarian oak barrels using medium to medium plus toast. The use of French oak was not added until our 2014 vintage. We have never used Quercus alba, or white American oak, in an effort to produce old world style wines.

The two main European oak species used for our wine barrels are Quercus robur, also known as pedunculate oak, and Quercus petraea, also known as sessile oak. Acorns on the Quercus robur are attached to branches by a little stem or oedicle, hence the name pedunculate. Acorns on the Quercus patraea sit directly on the branches, hence the name sessile which refers to sitting. Essentially, petraea produces barrel staves that provide pronounced aromatic character and low tannin content to wine while robur provides fuller body and more tannin structure while giving less complexity and elegance than petraea.

The two European species prefer different growing conditions. Robur performs best with more water richer soil and greater nutrition while petraea can survive will fewer amenities in thinner soil, colder temperatures and longer winters.

Many of the winery’s current barrel inventory features Quercus patraea oak sourced from the Zemplen forest in the mountains of northeast Hungary near the winemaking region of Tokaj. Tokal forests produce 95% petraea and are unequivocally unique and prized in Europe. The combination of cold climate, high altitude and volcanic soil create a species of tighter wood grain imparting greater aromatics. Petraea trees in the Zemplen forest are stressed for nutrition and water and grow mainly in the early season. Tight grain is always more aromatic because the aromatics develop in the spring or early season.