Even though in the past wine barrels used to be made from various noble tree species, like oak, mulberry, black locust, chestnut, white oak, coast redwood (USA), the reasons for this were largely practical, depending on the availability of good-quality raw material, as well as trade and political relations with the countries where adequate forests grew or barrels were made. Of course, the empirical part of the impact on wine was also present, both positive or negative, so some forests and sources of high-quality oak were known among barrel makers and wine producers. One of such places and a source of famous oak wood for making good large wine barrels was Slavonia.
The reason for this empirical selection has become easier to explain only with the rise of modern chemical analysis techniques, like gas chromatography and mass spectrometry, and their numerous derivations adjusted to a precise analysis of the composition and quantity of olfactory and gustatory molecules in wood. Furthermore, the development of precise techniques for measuring oxygen dissolved in wine, or the diffusion of gas through wood, provided answers to the question of why wine ages faster in some barrels, and why the origin of wood matters so much. In the case of wine, it all comes down almost entirely to discussing the origin of the most common barrels – those made from oak. Ellagitannins, tannins from oak wood, together with natural tannins from the grapes, create that desirable solid wine structure. And the distinctive aroma compounds of toasted oak, like vanilla, coconut, caramel, cloves, have become an inseparable part of today’s big red and white wines. They are discussed in the context of terroir and the expression of the wine itself, but oak also has its terroir and a specific expression completely unique to the place where it grew. Just as it is with the grapes, the “variety” of oak (species, subspecies, and form), soil, altitude, water availability, exposition, inclination – all these details make the origin of oak important.
These days, general discussions about the origin mention French, American and European oak, placing all oak trees coming outside the famous forests
of northwest France (Allier, Limousin, Troncais, Nevers, Vosges) into one mixed category where the origin is irrelevant. In reality, the French and the “European” oak are two separate species: sessile oak Quercus petraea and common oak Quercus robur. Both of these two, as well as dozens of their subspecies, forms, and hybrids, are perfectly adapted to their habitat, and each is unique in the characteristics it will pass on to wine: the density of wood and oxygen porosity, ellagitannins, aroma compounds. The American oak Quercus alba, with a low level of ellagitannins and a very high level of sweet aroma compounds, almost accidentally perfectly befits dense, concentrated, tannic Californian wines.
It was thus discovered that the famous Slavonian common oak Quercus robur (slavonica) features dense wood, medium to a high level of ellagitannins, and a lower level of aroma precursors. It is the ideal combination for making large barrels in which wine will age for a long time and which will be used for many years, slowly releasing tannins into wine, without any significant impact of oxygen and aroma compounds that would “impair” the recognizable fruit aromas in wine. Such characteristics, sometimes very desirable, especially in classic red wines that required long and slow aging and that abound in fresh tannins and acidity, are now overshadowed by modern wine trends and modern winemaking. Nowadays, grapes for red wines are harvested full of riper tannins, while the controlled temperatures of fermentation and gentler techniques of sinking the pomace have shortened the time needed for the wine to age.
Modern red wines made from the omnipresent Bordeaux grape varieties rich in their own tannins require aging in barrels made from wood with a lower level of ellagitannins, and most consumers ask for stronger toasted oak aromas as a sign of high quality in red wines.
However, maybe the time has come for Slavonian oak, too. Modern wine trends are eager to explore; they seek wine made from regional grapes; seem to shrink from strong oaky aromas; look for original fruit flavors; gladly accept elegant and subtle red wines, and maybe they are just about to give a winemaker the idea that the Slavonian oak would be ideal for their premium red or white wine. Maybe the given grape variety has no need for additional tannins from the wood and has interesting fresh fruit aromas and tannins that require long, slow aging. Or maybe we are talking about a rounded, concentrated white wine, one that needs longer aging in big barrels. Maybe you know such an “unknown” wine?