What Makes an Oak Barrel Neutral?

Several wine friends and I recently embarked on a discussion of how a new oak barrel becomes a neutral oak barrel. When reading wine labels, wine tasting notes, or visiting wineries and tasting rooms, one often encounters the term “neutral oak barrels.” Following the lively discussion with my friends, which involved some really good Texas wine, I decided to at least try to write down some thoughts on this subject, and possibly help our collective understanding of how barrels are used for aging, and sometimes fermenting wine. The key concern for me is how to define or categorize a neutral oak barrel when there seem to be so many ways to actually reach that neutral stage.

The starting point for an oak barrel would seem to be relatively straightforward, but there are a number of nuances to consider. Almost all wooden barrels or wooden tanks used for wine are made of white oak and there are two major types – American and European. The species of oak and the region where the trees grow can influence the flavor components the barrel introduces to wines, a situation not all that different from the terroir influence on where grapes are grown.

A cooper, or barrel maker, has the time-honored task of creating a liquid tight container (an oak wine barrel) from a pile of wooden staves. The staves are heated, traditionally over an open fire but more frequently now with infrared radiant heaters or steam, until they become pliable. The staves are then bent into the desired shape and bound together with metal rings. The heating process “toasts” the barrel which creates a number of flavor components from wood chemicals and brings them to the surface for eventual contact with the wine. The toasting can be light, medium, medium-plus or heavy, even charred (think Jack Daniel’s Whiskey barrel). Just dealing with new barrels is not so straightforward as one might assume.

Once the winemaker has a new barrel in hand, decisions need to be made on how to use that barrel. Decisions include what grape variety, which wine (red, white, bright & fruity, long aging red, etc.), and when the wine needs to be released for optimum drinkability. A winery’s cash flow issues and barrel storage capacity also play a role.

Many winemakers will tell you that after four years of use, a barrel will become neutral, meaning that little to none of the traditional flavoring that oak can contribute will remain in the barrel for extraction into wine. This seems simple enough, but most often the situation is a bit more complicated. One of the best, and funniest answers I have heard when asking a winemaker this question came from Jon Leahy at Becker Vineyards. His response to the question, “When does a barrel become neutral in your cellar?” was “Whenever I hang a Swiss flag on the barrel.” LOL

Perhaps the simplest way to categorize barrels is by the number of years they have been in the winery or cellar. For example, a new barrel purchased and first used in 2015 will become a four-year-old barrel after the 2018 vintage. If a different batch or cuvée of wine is aged in that barrel each calendar year, then not only is the barrel four years old, but it will have been used four times. I was involved in a barrel-fermented and aged Chardonnay program that used a limited number of barrels, cascaded down from new to 3-years old. The wine spent 6-8 months in barrel, was blended together, and then the barrels were cleaned and held until the next vintage. A few new barrels were added each year to the series of 1-, 2-, & 3-year-old barrels, while last year’s 3-year old barrels, now considered neutral, were moved to other uses. From this program, it was relatively simple to define the age and number of uses of the barrels, on an annual basis.

The first complicating factor in defining how a barrel became neutral is that wines often do not spend the equivalent of one season, or year, in barrel. If white wines are aged in barrels, the time typically ranges from a few months to maybe a year. With red wines, aging can range from a few months to 12, 18, or 24 months, even up to several years, depending on the grape variety, blend, or style that the winemaker wishes to achieve. So, is just using the years in a winery the best way to define barrel life, or could another approach be more useful?

For example, what if a winemaker uses a new oak barrel for just four months to add some rich, smoky, vanilla flavoring to a cuvée of Merlot? That barrel will still have a lot of “newer” oak flavoring to offer, and the winemaker might pull a Rhône-style blend of Mourvèdre, Grenache, and Syrah from older barrels and transfer it to this slightly used barrel. After another six months, the preferred amount of new oak flavoring has been achieved and this Rhône-style blend may be pulled from the barrel and stored in a tank until time for bottling. What then will be the fate of our first barrel, now used for less than one year? The winemaker may decide to introduce a Bordeaux-style blend of Cabernet Sauvignon, Merlot, and Petit Verdot to that newer oak barrel to soak up much of the remaining oak flavoring over the next 20 months before being declared ready for bottling and sale.

Are you confused by the example above? Probably, just like for many of us, there is now a problem in defining the history of the barrel. Three different wines have been in that barrel, and the amount of time it has been used to age these three wines measures 30 months. Is the barrel now defined by its three uses, or by the amount of time that has passed since first use? Is it a two-year-old or going on three-year-old barrel? Is the barrel now a neutral barrel?

If one further complicates the situation by using our example barrel for another vintage or two, with 2-4 more wines involved, it becomes even more difficult to define the history of the barrel and when it really became neutral.

The primary point here is to help folks understand what is meant by the term neutral, and how that can be defined. I hear people talking about neutral oak barrels after a couple of uses or maybe just two or three vintages in the cellar. As noted above, many winemakers believe that barrels have given up all or most of their oak flavoring components by their fourth year of use and are now neutral. Barrels that have only been used a couple of times, or for short periods with several wines, can still deliver oak flavoring to a wine, and are thus not what I would consider neutral.

My opinion on this matter has been significantly influenced by participating in that barrel-fermented and aged Chardonnay program noted above. It was pretty clear the wine from that vintage’s new oak barrels had lots of rich, oaky flavoring. The wine from last year’s barrels also had a lot of flavoring. What amazed me was that often wine from the third use barrels had the best flavoring balance – oak vs. fruit components. And yes, the wine from those fourth use barrels had the least oak influence approaching what I would call neutral.

If barrels used to age a wine are just simply described as neutral, you may not get a clear picture of what has transpired. A description of aging in what may be described as 100% neutral oak really needs further clarification to fully understand the flavoring components in a wine. If half of those “neutral” barrels were just one or two years-old, then there was most likely significant oak flavoring extracted from them into the wine. If all of those “neutral” barrels were 3-4 years-old, then certainly less oak flavoring would have been extracted, and expected in the wine. Perhaps larger back labels on wine bottles are needed to include all of this information.

There is at least one other issue to address when discussing neutral barrels. Through the natural porosity of wood fiber, oak barrels play two other roles for the winemaker, that being to allow 1) slow evaporation of liquid and 2) low level exposure to oxygen (from the air). Because oak wood is porous, evaporation reduces the amount of liquid wine in the barrel. The evaporated liquid is replaced with air containing oxygen that can help mellow tannins and mature various flavor components. Evaporation also reduces the amount of wine available – as much as 4-6 gallons of wine can be lost through evaporation each year from a typical 59-gallon (225 Liter) oak barrel. WOW! The “angels’ share” is the common expression used to describe this wine lost to evaporation. As liquid is lost, the resulting air space can dramatically increase wine exposure to oxygen, and perhaps cause premature oxidation or spoilage. For this reason, winemakers typically check their barrels on a frequent basis and refill with more wine during the aging process (a procedure called “topping”).

Over time, with successive uses, layers of natural deposits (primarily potassium bitartrate or wine diamonds) build up an interior coating in the barrel to limit oxygen transport through the wood, an important part of the wine maturation process. There are procedures that can remove significant portions of these deposits, thus refreshing the oxygen transport properties of a barrel. In this way, older, more neutral barrels can continue to have utility in the winery as storage vessels that help wine age gracefully. Selective use of different types, styles, and sources of oak barrels, as well as new vs. older barrels, provides the winemaker a wide range of flavoring options – commonly called the Winemaker’s Spice Rack.

After all this, there are still questions, at least in my mind, as to how best to categorize the history of a barrel as it traverses from new to neutral. At a recent wine tasting with Amie Nemec, proprietor of Perspective Cellars in downtown Fredericksburg, we were introduced to Charles and Diana Karren, proprietors of Land of Promise wines in Sonoma, CA. They grow exceptional Pinot Noir and Chardonnay, plus some amazing Cabernet Sauvignon. They not only produce delicious wines under their own label but sell Pinot Noir grapes to some of the top producers in California. Diana, originally from Russia, is the extremely talented winemaker, and during our tastings and discussions of her wines, she used a term that really caught my fancy. She described each use of a barrel in aging wine as a “passage,” and that sounded great. So, perhaps one could think about adapting a terminology to define barrel usage that might look like this:

Pinot Noir – oak barrel aging protocol, 20% new French, 40% one passage (18) French, and 40% two passage (36) French. This would define the new barrels, of course, plus single use French oak barrels that contained a previous vintage for 18 months, and two-use French oak barrels that had previously aged wine for a total of 36 months. Things could certainly get more complicated as more types of barrels that have been used more times get involved. However, this or some type of similar terminology might help to better describe what oak protocol was actually used, what oak flavor profile the winemaker had targeted, and how much oak flavoring should be expected in the wine.

The goal of this story is to get folks to think more about the term “neutral oak barrels” and appreciate that there is a lot of complexity inherent in this term. If you are a more casual wine drinker, you may not care so much about a better definition for neutral oak barrels, but since I am a dedicated “wine nerd” that loves all this technical stuff, I do care. And, this has been a musing on my part to address a topic which I would love to discuss with you over a glass (or several) of Texas wine when, and if, we next meet.

Acknowledgements: Several friends and wine aficionados participated in discussions on this topic. Their thoughts and opinions are much appreciated. Thanks especially to Laurie Ware, Bill Kreitz, Amie and Benjy Nemec, Barbara and Chuck Mauldin, and Bobbie Humphries.