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Wine & Oak: An Inseparable Pair

Recently I had the pleasure of watching Francis Durand, a master barrel cooper with the esteemed Radoux tonnellerie, build a barrel right on Deerfield's crush pad. It was an amazing experience and there were plenty of industry veterans, including Robert, who had never seen the process themselves. I videotaped the whole thing and you can check it out on Cellar Rat TV. I was fascinated by the process and it really got me thinking about the marriage between oak and wine. It is an element of winemaking that is easily overlooked. Trucks would arrive during harvest with dozens of beautiful new handmade barrels and as I helped unload them I gave little thought to the skilled craftsmen who created them or their enormous impact on the wine we were making. My perception of the grapes' journey to the glass had glossed over the entire art of coopering. The grape is grown in the vineyard and transported to the winery where it is transformed into wine and then bottled. I realize now that the fire and hammer of the cooper are just as much a part of that journey as the beaker and refractometer of the winemaker are.

Winemakers have known about the benefits of aging wine in oak for two millenia and the Roman Empire can be credited with expanding the usage of the material for constructing the barrel. There is no substitute for oak. There have been many attempts at using vessels made of other woods like cherry, pine, walnut and chestnut but none have the unique structural qualities and flavors of oak. In the barrel, oak is the right balance between hardness and softness that it is both durable and malleable enough to be shaped into a barrel. It is just porous enough to allow alcohol and water to evaporate through it, concentrating the flavor of the wine, and yet the grain is tight enough that it does not leak. The flavor that oak imparts is just as important as its ability to carefully expose the wine to minute amounts of oxygen. Compounds found in the oak and complexity yet also serve to stabilize the wine and its color. Oak further serves the winemaking process after it has been bottled. The cork tree is actually a type of oak, whose bark we remove to produce the corks so strongly associated with wine. While many alternatives, synthetic and natural, have been proposed, corks still seem to work best, allowing exactly the right amount of oxygen into the bottle to allow the wine to age gracefully. Since the beginning people have known that wine aged in oak tastes better but the science behind it has only been pursued for the last three decades or so. The process of "toasting" the wood, or putting the barrel over a wood fire fueled by more oak, adds a unique dimension to the wine. I had the opportunity to stick my nose in the barrel after Mr. Durand finished toasting it and it wasn't until I inhaled that enchanting aroma that I understood why wine and oak share such a bond - they both offer an incredibly complex and rich sensory experience that only improves when they are combined.

A Little More About Barrels

Several weeks ago I talked about the profound relationship that wine shares with oak and the importance of the barrel maker to the winemaking process. The artistry of bending the wood of the oak tree to benefit the crafting of wine extends well beyond the domain of the cooper. The winemaker chooses very carefully which vessels his wine will mature in. The choice is far more complex than simply whether to use French or American oak. At Deerfield, one of the key elements we use to create such nuanced wine is the implementation of what are known as barrel schedules, or programs. A great deal of thought and planning is done by the winemaker to create a schedule to add depth to the wine. Each wine rests in a variety of different barrels, so for example a lot of Cabernet Sauvignon, maybe even just one exemplary block in a vineyard, is given a custom-tailored barrel program. What's more, when that Cabernet is included in a blend years later, a new barrel schedule is created for that blend. What is incredible to me is the understanding the winemaker has of the impact on the character of the wine that a specific barrel has. There are three factors to consider in choosing a barrel for the program. The type of oak the barrel is made of: French, American, Hungarian oak, have very different flavors. Usually, at Deerfield, a wine receives a mixture of French and American oak barrels. The overriding idea is that when the barrels are later blended together, the attributes of both will be present in the wine. The second factor is the tonnellerie, or cooperage, that produced the barrel. There is a great deal of room for expression during the creation of a barrel - the heat and duration for which the barrel is "toasted" greatly impacts the flavor of the wood. The same barrel can even be constructed out of staves of different types of oak. Or all the staves can be one type of oak and the heads another. There's lots of variation and innovation within the cooperage industry, and though barrel making is a craft steeped in tradition, ongoing experimentation has invigorated competition among the coopers. During harvest, representatives drop by with a case of beer for the crew hoping to get the ear of the winemaker and tout the strengths of their barrels. Indeed, there are many to choose from. Demptos, Radoux, Bel Air, Tonnellerie du Val de Loire, Saint martin, Kovacs Tokai, Seguin Moreau, Quintessence, Magrenan, Kelvin Cooperage, Sylvain, World Cooperage, Emeritage, Boutes Tonnellerie de France, Trust, Tonnellerie Remond are just a few brands that reside in Deerfield's cave. Each chosen for its unique qualities and carefully monitored for performance. And then many cooperages tout different lines of barrels like models of cars - luxury, durability, longevity, leather seats. The point is you've got options. Lastly, the age of the barrel (in terms of its use) is a significant factor. When a barrel is brand new it has an intense oak flavor and any wine aged in it will assume that intensity. After about four years of wine sitting in it, a barrel has pretty much used up all of the oak flavor. Barrels that are old and no longer have noticeable oak flavor are referred to as neutral barrels. They are still useful - they impart tannins and remove harsher ones and allow the wine to breathe. So usually a wine is aged in a combination of new, 1 year, 2 year, 3 year, and neutral barrels so that when the barrels are blended back together for bottling (or further blending) the resulting wine is well balanced. Also this gives the winemaker options for different blends. Perhaps a Tuscan style Sangiovese blend would benefit from a Cab Sauv that has been aging in  new barrels. Here is part of the barrel schedule for 2009. On the head of most barrels you can see the type of oak, the year the barrel was made, the cooperage and the amount of toast. If you stop by the cave take note of what barrels are being used for each wine.

Punch It!

Last week we talked about how the grapes are sorted once they arrive on the crush pad. So what comes next? The sorted grapes are ready to be fermented at this point. We use two types of containers to ferment the fruit in, large stainless steel tanks and smaller plastic bins. Red wine goes through primary fermentation with the grape skins, which is where the vine gets its color. In fact, you can actually make a white wine from a red grape if the juice is immediately separated from the skins. Much of the tannin that gives red wine its structure is found in the skins so it is very important that the fermenting juice, or must, is in contact with the skins.

The skins float though, so they constantly rise to the surface forming a thick layer we call the cap. In order for the skins to fully transfer the flavor to the must, they must be re-submerged periodically, usually several times a day for the full duration of fermentation. This process is called a punchdown. You may have seen pictures of people on top of vats of grapes, holding themselves up while using their feet to push the skins down. Well we don't use our feet anymore but I guess the name stuck because the tool you use to punchdown the cap is called a foot. They come in many sizes and shapes but are usually just a rod with a flat surface with holes in it at one end. We've got several varieties of them here at Deerfield and I think everyone has their favorite one.

During crush we often have as many as 40 lots of wine fermenting at one time. Our protocol calls for each of these lots being punched down twice a day. So usually while the majority of the crew sorts fruit, one lone cellar rat goes from bin to bin punching down the skins. By the time you get done with the last one it is usually time to go back to the first one and start again. It's quite a work out. Sometimes it's as easy as pie but occasionally the cap is compacted and more than a foot thick. Perched precariously on the thin lip of the bin, wearing slippery galoshes, you throw your full weight onto the foot. Suddenly the cap gives way and you feel all resistance disappear. Falling into the delicate fermenting fruit is not an option so desperately you lean backward to regain your balance. Phew! Repeat another 40 times. The cap of the large stainless steel tanks is often too thick to punch down by hand so we use an alternate method which we call a pump-over that I'll go over next week.

Or Pump It!

The alternative to the punchdown technique I discussed last week is what we call the pumpover. If the cap is too thick to punchdown by hand or the winemaker thinks that the fermenting wine needs to be more thoroughly mixed, we use this method. We have a large hydraulic “foot” that attaches to our forklift that we can use to punchdown the large stainless steel tanks but for the most part we perform pumpovers on the tanks.


A cylindrical stainless steel strainer is inserted through the cap at the top of the container. This can be really difficult sometimes if the skins are too compacted. As soon as the strainer breaks through, the juice comes bubbling up to the top. Then one end of a hose is inserted into the strainer, which is long enough so that the hose can reach the liquid well below the cap. Using one of our powerful compressed air pumps we pump the juice over the top of the cap evenly for about 15 minutes – hence the name. This way the skins stay wet and the must at the bottom of the vat is able to come in contact with the skins. This adds enough oxygen to the must for the yeast to survive, stay happy, and do their job. Occasionally the juice gets sucked out of one area and the strainer needs to be moved around.


Pumpovers are much easier to do than punchdowns. The downside is that the pump must be cleaned between each pumpover. The foot that is used for punchdowns is easy to rinse and spray down with alcohol. But the pump must be taken apart, the remaining wine drained out of the machine and the hoses, then added back to the tank (only about half gallon, but it adds up after several weeks). Then the pump is reassembled and a proxy solution is circulated through it, then a citric acid solution and finally water. Once again it must be taken apart, and the hoses drained. Finally it is reassembled for use on the next tank. After doing this about a hundred times you get very fast at it but it still can take longer to clean the pump than it does to actually use it!


Personally I like doing pumpovers better than doing punchdowns just because the risk of falling in the bin and ruining the wine is stressful. So far we’ve covered sorting the fruit and one aspect of the primary fermentation process. The journey continues next week on!

Nice Rack

Winter can be a lonely time for a cellar rat. The hustle and bustle of harvest has faded away and the wines are sleeping in the cave. Outside the air is almost freezing, making the 60 degrees of the cave seem cozy. Most of the work during the off-season can be done solo, leaving you with the barrels as your companions.

In this post I talked about the endless process of keeping the barrels topped. With 2500 barrels to keep full to the brim there’s plenty to do. The other major process that takes place year-round is called racking. Racking is another element in making clean wine. Cleaning the barrels throughout the process reduces the likelihood of bacteria or mold affecting the wine. It’s a technique that’s been used for thousands of years. It involves moving the wine from one vessel to another. There are several reasons that racking is useful to the winemaker. After fermentation and the grapes are pressed, small solid particles, including the yeast, remain present in the wine. These sediments slowly settle on the bottom of the barrel like silt does on a river bed. Instead of trying to filter these particles out, we simply draw the wine off of the top of the sediment and into another vessel. This mixture of yeast and other particles is known as the lees. You may have seen a wine label mention that it was aged sur lees. This essentially means that it was never racked.

It’s for this reason that we have closed top stainless steel tanks as well as open ones. During fermentation the reaction creates enough CO2 to protect the juice from oxygen. Afterwards the wine must not be exposed to oxygen in large volumes, so the wine is racked from the barrels into the controllable environment of the tank. Often we pump nitrogen through the wine, essentially pushing the oxygen out of the liquid and filling the remaining space in the tank. Then we rinse the barrels using a specialized hose attachment that’s really just a glorified sprinkler. Then we steam clean them which uses only 2 gallons of water compared to the 22 gallons that are used during conventional hot water cleaning. When the barrels have been cleaned and drained the wine is returned to them. This process usually gets repeated several times before the wine is bottled. With each successive racking the wine becomes more and more clear. We call it clarification. Additionally to finish the process, we have high quality filtration technology which removes microscopic solids giving the wines a jewel-like characteristic.

The challenge lies in the fact that the large tanks are outside and the barrels are all inside. The barrels are all packed into the cave like a jigsaw puzzle and removing a particular barrel often means moving an entire row to get to it. It’s the winemaker’s job to plan where to put the barrels and when to rack them but it’s the cellar rat’s job to get the barrels out! I must admit that I admire our Cellar Master Aron’s ability to maneuver the forklift in the close quarters of the cave.

Until next time! Salut!