The following text and photos are contributed by Flying Goat Cellars Ambassador Faye Walker:
The Scoop on Cooperage
The barrel making process, known as cooperage, is a significant part of wine production. Different techniques of bending, heating, and building wooden staves into barrels are known to affect the sensory aspects of wines as they age in various oak barrels. Everything from alcohol content to color composition to odor could differ. The terminology of "new" versus "neutral" oak is often bandied about in relation to some of these characteristics related to wine ageing. What's the final outcome when it's time to bottle the wine? The dividing line between a bright and zippy tang versus a textured and creamy blend owes much to the cooper--and we're not just talking about the resident pinot puppy at Flying Goat Cellars.
Oak Species and Grain
Much like vintners and grapes, cooperage begins with selecting wood from a particular geographical region. The international market is largely dominated by the use of French and American oak--though offerings from Hungary, Russia, Slovenia, and Spain are also incorporated for their own finished effects on wine. Even within one forest, the wood coming from each tree can be very different. Some species may prefer rich soil and low elevation, while others adapt to the dry conditions of hills and slopes.
How does the wood indicate how a barrel will actually interact with the wine? As oak trees grow, the sap flows with minerals, nutrients, and sugars throughout the grains. Certain oak species tend to have their own sets of sensory properties. Oaky aromatics are typically described as pastry-like, vanillin, and whiskey lactones. These aromas are released from the wood grains in the barrels over time; in addition, oak tannins are also released into wine.
The origin of a forest accounts for one set of barrel properties. Another important contributor is the seasoning, shaping, and toasting of the wooden staves to constitute the barrel structure. Seasoning is an air-drying process (2-3 years) that accordingly modifies the extractability of oak-derived compounds into wine. Subsequent steps of shaping and toasting are considered critical in determining the physical and chemical composition of staves--and thus of the makeup of any wines aged within.
In particular, oak-derived compounds that have a sensory effect on the finished wine include lactones (milky and creamy), furanones (jammy), phenols (sweet), and pyranones (caramelized fruit). Such phenolic and volatile compounds are imparted during the stage of oak barrel maturation. Barrel aging is considered to produce wines enriched aromatic substances with high-quality characteristics.
Foundations and Experimentation
For all of its tradition and distinction, ageing wines in oak barrels remains an expensive undertaking. French coopers sell barrels by forests to emphasize their natural, non-artificial growing environment. Their barrels cost at least $1,000-$2,000 apiece. Adding on the fact that barrels have finite lifetimes of 5-10 years, costs can quickly skyrocket for a cellar.
Alternatives have been developed to simplify the ageing process while keeping the effect of traditional oak ageing systems. To this end, winemakers have turned to the option of adding small pieces of wood to wine kept in stainless steel tanks. This makes it possible to assess the influence of different oak delivery methods on the overall profile of wines stored under variable conditions.
Weighing Wood's Importance
At the end of the day, is wood worth its weight? Chemically speaking, there is a clear separation between wines aged in wooden barrels versus other vessels. Within that, there is also a distinction between new and neutral oak. When it comes time to say whether the spicy or buttery notes come from a distinct grain type of forest origin, the lines of distinction become blurred. One thing is for sure: there is a lifetime of discovery that exists in the interplay between barrels and aged wines. We look forward to sleuthing and sussing out the cooperage that elevates our Pinot fruits in the best possible way!
Sources and Further Reading:
Casassa, L. F. et al. "Detailed Chemical Composition of Sauvignon Wines Aged in French Oak Barrels Coopered with Three Different Stave Bending Techniques." Food Chemistry 340, 2021.
Cfp-vs. Wikipedia. "Lactone." https://en.wikipedia.org/wiki/Veraison
Gordon, Jim. Wine Business Monthly, 2019. "Does Oak Grain Still Matter?"