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Aging Vessels | What & Why?

When you think of an aged wine, do you immediately think of an oak barrel? Or a clay amphorae? Or perhaps a giant steel vat? Chances are the majority of wine drinkers imagine their (red) wine aged in oak, but the truth is: there are many options for aging wines!

In this post, we'll explore a few of the most common types of vessels and the role they play in a wine's flavor, body, and texture.

Oak Barrels

In regards to oak, it's not uncommon for me to go down the rabbit hole on this particular topic: types of oak, toasting methods, grain structure, etc. But for the sake of the reader, I'll try to keep the information succinct.

  1. Purpose of using oak: Oak barrels are used in order to impart “oak characteristics” into the wine. The 3 key characteristics are: flavor, structure, and tannin. Maturing wine in oak barrels allows for a gradual oxidation process because the wood material is porous (breathable) which allows oxygen to seep into the wine at a very slow pace. This process of oxygenating the wine helps add body and the development of flavors (in the case of white wine, it mellows the primary fruit flavors; for red wine, it helps integrate tannins and adds a roundness after the process of MLF (malolactic fermentation)).

  2. Barrel Size: Two traditional sizes of oak barrels are the Foudre (up to 1,000 L) and barrique (225 liters, although Burgundy uses 228 L barrels). The smaller barrels impart more oak characteristics into the wine due to the smaller surface area to volume ratio. In a Foudre barrel, since the surface area to volume ratio is smaller, the level of oak flavor is limited and thus not as up front on the palate.

  3. Toast Level: If you were to taste a red wine matured in a highly toasted oak barrel and a red wine from a lightly toasted oak barrel, I can almost guarantee that you would tell the difference! The level of toast in an oak barrel determines the intensity of the vanilla, spice, and smoky aromas and flavors. There are three toast levels, with the third being the most toasted (a dark char on the inside). As you may have guessed, the more toasted the more flavors of vanilla, baking spices, and smoke influence the wine. The level of toast in the barrel depends on the winemaker’s goal for the finished flavor profile.

  4. New vs. Old Barrels: Whether or not the barrel is new or old has a very great influence on the wine! Newer oak barrels (those that have not yet been used) are fresh and hold a lot of oak flavor and impart much oaky characteristics of the wine. Older barrels (at least 3 years old) can be used to impart less flavor. After a barrel's first use, it loses 50% of its oak flavor and thus, imparts less and less oak characteristics into the wine after each use. New barrels are also quite expensive, especially for certain types of oak. A typical American oak barrel may cost around $500 whereas a French barrel can be up to $1,000 or more!

  5. American vs. French Oak: American oak and French oak are the two main varieties that are most commonly used for barrels. French oak is known for its gentle flavor profile of vanilla, spice, toast, and caramel; American oak is known for its more robust flavor profile of sawdust, lime, coconut, and vanilla. But again, newer oak regardless of the type of wood will have less of a flavor impact. French oak barrels are more expensive to make than American oak barrels due to the longer period of time it takes for the trees to grow and in accordance with French laws, only a certain portion of the oak trees may be cut each year. French oak must be hydraulically cut along the grain in a certain manner to avoid leakage in the barrel. Since American oak is less porous than French, it can be sawn and grows relatively faster.

Other Types of Oak...

Slavonian Oak: In Italy, mainly in the NW region of Piedmont and also in Tuscany, Slavonian oak is used at numerous wineries due to its tight grained wood which allows for very minimal oak characteristics to be imparted into the wine and the oxidation process is slow and limited. Though at first glance it looks like "Slovenian", Slavonian oak is sourced from Croatia! This particular species of oak, with its tight wood grain, is perfect for Italian wines that rarely if ever taste overwhelmingly like toast and vanilla. The tight grain and typically larger oak barrels used for aging allow the Italian wines, notably tannic Nebbiolo and Sangiovese, to retain their velvety tannin without being bombarded by the oak.

Hungarian Oak: Hungarian oak is actually the same species as French oak but imparts more tannin and structure due to its grain makeup. Similar to French oak, Hungarian oak imparts flavors of spices (savory) and depending on the level of toasting, warm flavors of vanilla and baking spices such as clove and cinnamon. This oak is harvested from forests in Slovakia, Hungary, and parts of Romania.

Steel, Concrete, and Clay

In addition to wooden vessels, steel, clay, and concrete are also often used for fermentation and maturation of wines. Winemakers may elect to use these vessels in lieu of wood in order to maintain the primary fruit flavors and aromas. Or, these alternatives may be used based on financial constraints of smaller producers or for high volume wine producers who wish to bypass the waiting time of oak aging.

  1. Stainless Steel Vats: Stainless steel vats are often used when a winemaker wishes to maintain the freshness and primary fruit flavors of a wine since steel vats are inert ( no oxygen seeps into the wine). Most steel vats now are high tech and can be temperature controlled through a computer system. This, obviously, makes for a somewhat easier time of keeping track of the wine’s temperature and overall state during maturation. Both red and white wines can be fermented and/or aged in stainless steel. If a winemaker wants to age a wine in steel but still add flavors of oak, he/she may opt for the use of oak chips or oak staves coupled with micro-oxygenation. While oak chips and staves are a more financially feasible choice, they do not impart the same intensity of flavors of a natural oak barrel. And the use of *micro-oxygenation aids in the development of the aromas and flavors of the wine and help further impart the oaky flavors as it means to replicate the slow oxidation/oak imparting process of a barrel.

2. Concrete Eggs: Another slightly porous vessel is the concrete egg. And yes, “egg”

is the correct term for these vessels as they are, in fact, shaped like an egg! The oval

structure allows for a natural convection of the wine during maturation and thus it does

not need to be stirred or require the other “cap management” methods of an open

steel or wooden vat. Similar to a wooden barrel, concrete is also a challenge to clean

due to its porous nature and it does experience staining just like oak barrels; so, once a

red wine is used on a concrete vat, there is no choice to reuse the vat for white wines.

Another drawback of a concrete egg is that the egg may be susceptible to cracking if

there are rapid temperature variations. Concrete does not impart much flavor at all

which allows for the wines to maintain their fresh and natural flavors while still going

through the fermentation and/or maturation process with MLF or on lees, depending on

the winemaker’s goal. If the wine is meant to spend time on its lees, in the case of white

wine, the dead yeast cells (lees) are suspended in the wine rather than settling at the

bottom of the vessel. Additionally, the tartrates that form (wine diamonds) stick to the

sides of the concrete rather than float among the wine. The suspension of yeast cells

helps to impart the leesy flavors in the wine limiting the bitter or off flavors that can

occur if wine is left for too long on its lees at the bottom of a vessel. Concrete eggs are

also slower to heat up and thus, the wine goes through a gradual warming process and

is not likely to overheat or cook the wine. *Illustration by Wine Folly.

3. Clay Amphorae: Amphorae or Qvevri, while looking like a fancy word, is one of

the oldest wine maturing vessels! Originally created and used in Georgia (the birth

place of wine), the clay vessels were used to ferment wine by being buried underground

to help limit the amount of oxidation to the wine. While these vessels may look

intriguing to the eye and are a nod to the traditional methods first used in Georgia (the

country, not the state!), they are expensive to make and are quite laborious to create

wine as there are no valves or hoses and only a small opening at the top of the vessel.

However, for making a wine without imparting any of the vessel’s flavors, this is another

great option along with stainless steel.

If you've made it this far, congrats! That was a lot to take in. I think now is the time for you to rest your eyes, relax, and enjoy a glass of wine.

*Micro-oxygenation: the process of adding oxygen into an inert vessel of wine in order to develop oxidative aromas and flavors. For this process, a small tube with multiple tiny holes is inserted into the vat and oxygen is run through the tube which then bubbles into the wine.


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