Time & temperature barrel profiling: create consistency & individuality in wine barrels

Most wines benefit from aging in oak barrels. Aroma and flavor are enhanced, while color is stabilized. Plus, there is a greater overall impression of complexity. Historically, barrels were re-used extensively, so there was often no obvious presence of oak. However, today's consumer is more demanding, and expects more complexity. This can include toastiness, vanilla, a touch of smoke, spice and soft tannins. The toastiness is from the caramelized sugars that result when the barrel is heated. The vanilla derives from oak lignin.

Toasting barrels over open fires made with oak pieces is still the order of the day, but the process struggles to create a high level of consistency for today's wines. Until now, the only means of controlling the flavors being created in the toasting process was the darkening of color inside the barrel. However, most of the flavors that result during toasting are totally colorless, so the relationship is, at best, an indirect one.

During the long history of barrel cooperages, each developed its own design of fire pots. Individually, the cooperages decided how long to leave the barrels over the pots and how much heat to apply. These individual toasting regimes are responsible for most of the differences in flavors from one cooperage to another. It is true that grain tightness, seasoning time and oak species all have roles in the overall flavor. However, it is the exposure of oak to heat that brings about major chemical and physical changes in the wood. These are massive in flavor creation, compared to any of the other factors.

The development of time-temperature barrel profiling by World Cooperage has changed the reliance on some ill-defined toasting regimes, creating what is probably the most significant innovation in barrel-making since the wooden heads replaced animal skins in Egyptian times. So what is time-temperature barrel profiling? How does it create unheard-of consistency? And how can we reconcile consistency with individuality?

With product profiling installed at its cooperage, World Cooperage still uses open fires to bend and toast the barrels. The company uses its own unique toasting pot and its own toasting regimes. For some years now, this has allowed it to offer four styles of barrels. These include:

* The original, World Cooperage traditional barrel

* The Legacy barrel by T.W. Boswell, with a toasting regime of shorter time and more heat, to create a typical French oak barrel

* The Medoc French oak barrel by T.W. Boswell, with a toast based on a very short, high temperature that's designed for full-bodied reserve-style wines

* The Cote d'Or French oak barrel by T.W. Boswell that follows the Burgundian practice of applying a lid to the barrel, whereupon heat is forced into the oak staves and the profile of flavors in the depth of the staves is minimized

Creating Better Consistency

The new profiling technology began with a series of 20 of each of the above-mentioned barrel styles. Each barrel profile was created by carefully using the historical toasting regime but, in addition, the temperature inside each barrel was measured and recorded every few seconds. Once these barrels had been tried, tested and pronounced by winemakers as true-to-type, the time-temperature recording was used to make all future barrels.

Figure 1 shows how the toasting temperatures vary between the four styles of standard barrels.

At the same time, the toasting pots were re-engineered to rotate, allowing better distribution of heat around the inside of the barrel. An infrared temperature sensor was installed at the base of the fire. This sensor records the temperature on the inside of the barrel near the bilge. The time-temperature recording is displayed on a monitor screen beside the person toasting, and he follows the process curve so that an exact copy of the original will be created. That is how the unique consistency is achieved.

Visitors to the cooperage with a passing knowledge of barrel making might notice no difference at all from other cooperages. The coopers are busy toasting the barrels, still without ends, over open oak wood fire pots, as normal. But on closer inspection, the visitor would see touch-screen monitors above the toasting area, and temperature sensors inside the pots.

Creating Individuality

There is no reason why barrels have to follow any of the four standard curves, as long as it is realized that this will change the ultimate flavor of the wine. If a winemaker wants something different, and knows what he or she wants, perhaps a spicier or a low tannin barrel, then a personalized toasting curve can be created in which the barrel spends more time in the appropriate temperature regions.

To create a custom barrel requires, first of all, clear communication from the winemaker. Secondly, it relies upon World Cooperage's knowledge of the temperatures that create particular flavors. And thirdly, it depends upon software engineers being able to produce the time-temperature graph. To date, more than 70 custom profiles, dictated by the wishes of winemakers, have been created. The correct-first-time success rate is better than 80%.

The example on page 26 was the second custom profile designed, and demonstrates how a profile specific to a single winery can be created. In this case the winemaker liked the rich vanilla flavors and relatively low level of toasty flavors that the Medoc barrel imparts to full-bodied red wines. However, the winemaker did not want to keep his wine in barrel long enough for the high amounts of large oak tannins that come from the Medoc barrel to soften and integrate with the wine.

A sample of the wine was analyzed for 26 oak- and wine-derived flavor compounds. This is the normal analysis that World Cooperage undertakes on oak-aged wines. This list is shown on page 24.

With the results from this analysis and the winemaker's sensory requirements, a new time-temperature curve was produced. This is shown in Figure 2.

During the following harvest, the wine was produced as usual, and a percentage was aged in the new custom barrels. The experiment was pronounced a complete success. How was this change achieved? The first section of the time-temperature profile in Figure 2 is the same as the Medoc toast (see Figure 1). Instead of ending at a high temperature, the custom barrel was cooled quickly, down to a temperature region where tannins are destroyed with no further flavor creation. The resulting new profile did not impart nearly as much oak tannin to the wine, and the softer effect allowed the wine to be marketed earlier.

Creating an individual barrel by custom profiling involves a close partnership between winemaker and cooper, and it opens up new opportunities for the creation of styles to meet winemakers' needs, as well as a major improvement in barrel consistency. The innovation combines engineering, sensory and computer sciences to achieve:

* Accurate temperature measurement in toasting

* The creation of computer-aided guidance for coopers

* Analytical capabilities to measure chemicals that control flavor development and techniques to correlate sensory and analytical data

Once the custom profile is created, it can be easily reproduced at the cooperage. It is simply a different curve on a monitor screen for the cooper toasting the barrel to follow.

The goal of barrel profiling is to provide consistency in flavors, as well as the ability to customize flavors for specific wines, wine styles and vintages. As winemakers take advantage of World Cooperage's barrel profiling technology, they find they are able to achieve dependable, repeatable flavors, and say they are enthused about their own, tailor-made barrel profiles.

RELATED ARTICLE: Oak And Wine-Derived Flavor Compounds

Tannins & breakdown

Gallic acid

Ellagic acid

Vescalagin

Castalagin

Hemicellulose breakdown

5-hydroxymethyl furfural

5-methyl furfural

Furfural

Wine phenolics

Protcatechuic acid

Catechin

Epicatechin

Chlorogenic acid

Caffeic acid

Myricetin

Quercetin

Lignin degradation compounds

Vanillic acid

Syringic acid

Vanillin

Syringaldehyde

Coniferaldehyde

Sinapaldehyde

"Smoke" phenols

Phenol

Guaiacol

o-Cresol

4-methyl guaiacol

4-ethyl phenol

4-ethyl guaiacol

Oak Lactones

trans lactone

cis lactone

Dr. Jim Swan

(Dr. Jim Swan holds a Ph.D in chemistry and biological science, and consults with winemaking and distilling companies worldwide. He has worked with World Cooperage research and development for 12 years. Contact him through edit@winesandvines.com.)

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