Education
“Roll Our the Barrel” Second Verse
by Stephen Pavy
Let’s start with a quick recap of the “First Verse” (last month’s article). The aromas and flavors in wine come from three places: from the grapes and vines themselves; from the fermentation process; and from the barrels. Three basic changes occur in a wine as it matures in a wooden barrel: 1) alcohol and water evaporate through the sides of the barrel, concentrating the wine; 2) some oxygen dissolves in the wine, allowing oxygen-dependent maturation reactions to occur slow (micro-oxidation); and 3) substances from the wood are extracted out into the wine.
This month we look at what is extracted from the barrel. Modern research methods have identified well over 70 volatile compounds that can be extracted from oak into wine as the wine is aging in barrels. Using a gas chromatograph/mass spectrometer, it is possible to isolate these compounds. It is, however, much more difficult to understand what is going on in barrel extraction, much less control it. Nadalié USA, a cooperage located in Calistoga and founded in 1980, has led in the research of how oak aging affects wine and has made some of their research available to the public and the industry.
Of the more than 70 compounds, Nadalié has focused on nine of these compounds: Cis-oak lactones and Trans-oak lactones; Furfural and 5-Methylfurfural; Vanillin; Eugenol and Isoeugenol; Guaiacol and 4-Methylguaiacol. The important thing here is to understand that these nine compounds can create the following aromas and flavors when the barrel is properly crafted and toasted: raw oak, woody and coconut; sweet and light caramel and butterscotch; vanilla; spice, cinnamon, and clove; smoky and charred. The other compounds not analyzed in Nadalié’s research are responsible for many of the other barrel-extracted aromas and flavors.
So how do you know what you are getting? How do you know how long to leave the wine in the barrel? That is where the art of winemaking comes in. Science can tell us some things, but it can never produce a “recipe” of “How to make wine.” So much of winemaking is understanding the fruit you have harvested, having experience with good yeasts have worked for you, and understanding the choices and uses of barrels. Which barrels you might select will depend on personal winemaking style plus a wealth of experience that you can draw upon to understand what barrels from specific cooperages will probably result in certain aromas and flavors.
Art, experience, and “taste”: there is no substitute for tasting the wine in barrels frequently and deciding how they are doing and how long they should remain in the barrel. The wood extracts will move into the wine through direct diffusion from the wood barrel into the wine. Transformation also occurs when certain non-volatile compounds are transformed into volatile compounds, usually by yeast and bacteria. These processes take time and depend on the source of oak, the type of coopering, the amount of toasting, and the conditions under which the barrel-aging takes place.
Let me give you an example. I want to cite a new wine that St. Francis has released this year: the 2002 McCoy Vineyard Malbec. This wine spent a total of 24 months in oak barrels. The barrels were all French Oak, but only 30 – 40% were new, the rest were in 1 and 2-year old barrels which will impart much less aroma and flavor to the wine. The cooperages that were used were Boutes, Berthomieu, and Sansaud.
Each of our wines aged in barrels has a fairly complicated “barrel regime”. That is, the wine is stored in barrels from different cooperages and different percentages of new versus 1- and 2-year old and sometimes completely “neutral” barrels. Sometimes the wine is “racked and returned” to the barrel. Sometimes it is simply topped and periodically tested and tasted.
Some other fun facts: if you store wine in an environment with about 80% relative humidity (RH), the rate of water and alcohol loss is about the same. If you store a barrel in a low humidity condition (less than 80% RH, and some storage areas can be very dry), the rate of water loss increases and you will lose more water than alcohol. The result here is a wine that is more concentrated than when you started (less water), but one with a greater alcohol by volume. If you store a barrel in a high humidity condition (greater than 80% RH), the rate of alcohol loss increases in relation to the water loss and you get a wine that is still more concentrated than the one you started with, but has a decreased alcohol by volume.
When you lose wine in the barrel through evaporation (called “ullage”), you will need to go around periodically and “top” the barrel with the same wine. This prevents an air space from developing and creating an environment where spoilage organisms can take hold and develop. When you top a barrel, it is a good time to take a sample to the lab for testing, and a good time to taste the wine to see how it is doing.
Next month, the last in our barrel series: sources of oak and coopering.
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