A barrel of…questions

A few weeks ago, Cy and I were having lunch when he had a question about oak barrels and winemaking. Is wine ever aged or stored in barrels made from other kinds of wood? You’d think it could be, right? I didn’t have an answer then, so I did a little research.

It turns out that this is one of those things where the universe converges on one right answer because of the way barrels are used in winemaking and their shapes. Once you eliminate others because of various issues, oak is the wood of choice, particularly from oak trees grown in cooler climates, like France and the northern U.S.

Wood used in making barrels has to be bendable, but not too bendable, to give the barrel its characteristic shape.  The staves of the barrels are usually softened by heating with an open flame, which also toasts the barrel, adding flavor to the wine.

Wood used in making barrels has to be bendable, but not too bendable, to give the barrel its characteristic shape. The staves of the barrels are usually softened by heating with an open flame, which also toasts the barrel, adding flavor to the wine. (Photo from winefolly.com)

There are four criteria for using wood in barrels in winemaking:

1) It has to hold the wine without leaking.

2) It has to be slightly porous to air.

3) It can’t impart unpleasant flavors or odors to the wine.

4) Finally, because of the barrel’s characteristic shape, the wood has to be bendable.

Let’s take these four in order.

Watertight. Any wooden container could be coated to be leak-proof, either on the inside or outside. But an inside coating would make the container pretty much airtight as well as watertight, so air wouldn’t diffuse inside (we’ll get to that one below). An outside coating would do the same thing, only the wine could pick up unpleasant odors and flavors from the wood. So without a coating, this generally means a hardwood over a softwood.

Hardwoods are “hard” because they’re dense and their fibers are stronger. When trees are harvested the wood is fairly wet and has to be dried, either by natural evaporation or by heat drying. The wood fibers shrink as the liquid evaporates out of them, and wood in general becomes more watertight as it’s dried. But hardwoods have more fibers per square inch to begin with. This means even less air space between the fibers after drying, and less chance for liquid to pass through.

Two other considerations are important: fewer knots and what’s called close graining. The knots are created because of branching. Knots look nice, but they reduce strength and make the wood less watertight. So tall, straight trees with very few branches are key. Then there’s the grain structure of wood. Hardwood trees that are grown in cooler climates are denser and shrink even less when dried. Their structure allows cleaner cutting both with and against the grain. The longer dormant periods and ability to resist the cold in cooler climate zones makes all of the trees more close-grained, and this is desirable for barrel making.

Porous. This seems contradictory to water-tightness, but it’s important that air diffuse into the barrel to interact with the wine — but not too much of it. So it can’t be airtight, but it also can’t let too much air inside. The oxygen in the air reacts with various molecules in wine to enhance flavor and reduce bitterness from the wine’s tannins. But too much oxygen would also cause the wine to oxidize (like sherry) and spoil in other ways. The sulfites used as a wine preservative work largely because the wine isn’t exposed to a lot of air for long periods of time.

Equally important is the barrel’s ability to let some of the wine diffuse out. A little of the liquid will evaporate and escape through the barrel. The loss of liquid volume concentrates the remaining flavors. A wood’s porosity depends on its structure, and hardwoods are less porous than softwoods. They allow just a little air in, where a softer wood would allow more. Likewise for vapor diffusing out.

Odors and Flavors. While some people find the wood/vanilla/spice flavors that oak barrels give wine objectionable, they’re tame compared to what other woods would do. From horrible muskiness to astringent tannins to resins, other woods give some pretty awful odors and flavors to liquids inside them. Even fruit woods, like apple and cherry, don’t work. Pretty much any wood you’d use to smoke meat will give wine undesirable odors and flavors. And while oak has a lot of tannins of its own (which make it insect-resistant), these don’t add much astringency to the wine, but do help prevent oxidation.

Most wineries have rooms for storing wine as it ages in barrels, although they're not all as elegant as this one, at the Château de Mercues near Cahors in France.  But they all have an intoxicating smell that's a combination of oak and wine.  If I could find a way to make my house smell like that, I would!

Most wineries have rooms for storing wine as it ages in barrels, although they’re not all as elegant as this one, at the Château de Mercues near Cahors in France. But they all have an intoxicating smell that’s a combination of oak and wine. If I could find a way to make my house smell like that, I would!

Shape.  There are a couple of schools of thought on why barrels are shaped the way they are. One is for ease of transport — the bulge in the middle makes them roll more easily. Less material touching the ground or floor means less friction, and less work to push them. This is important, because no one wants to lift a heavy barrel to move it.  We’ve all seen the pirate movies where barrels are rolling down a plank from the ship to the dock. It actually works! And what about that “Roll out the Barrel” song? You’d better believe it would be a lot harder without that bulge.

The second is that the slightly rounded shape of the barrel means more surface area per gallon of wine inside than if it were a regular cylinder. The more spherical, the more surface area to volume. More surface area means more air and more flavors from the wood. But making them too round would be difficult and impractical for storage.

So if they’re going to be slightly rounded, the wood has to be bent to shape. Really hard woods like redwood are extremely difficult to bend. Wood for barrels gets bent either by steaming the pieces or by heating them over an open flame. The flame also chars the barrel a little, even if it doesn’t look like it’s charred, and charring adds its own flavors.

Put all of these together and you’re left with oak. And if you’re going to be using one particular tree, why not choose the one that symbolizes strength through much of the world? There’s a lot more to say about barrel size, age, and origin, but they’ll have to wait. You’ll have enough to do trying to get the song out of your head!

Can you believe this was actually a Top 40 hit in 1975?

———————————–

As I was writing this I found myself wishing we had two identical wines, one aged in oak and the other not, so you could compare them side by side and see the difference. While we have some wines from the same producers that are aged in oak or not, there are other differences — mostly older vines in the oak-aged wines — that make this direct comparison impossible.

So instead I’ll just put our most elegant oak-aged wine out there, the Tuscanio Rosso 2009 from Società Agricola Bulichella in the Maremma in Tuscany ($35). It’s 100% Sangiovese, from the best vines on the property, aged 18 months in oak then a year in the bottle before release. Truly a wonderful wine — so good that the Food and Wine magazine’s Italian wing declared it the best Sangiovese in Italy last fall. Better than Sangiovese from the Chianti regions. It’s made with organic grapes, and we’ll be getting the certification paperwork for future orders so we can label it that way.

It’s a big wine, and that means you need pretty intense flavors with it or the food will be overpowered. So go ahead and have your steak or roast. But blue cheese is also a great pairing, so why use it in a side dish?  I was looking through recipes I’ve clipped from newspapers over the past few years and found a savory tart with blue cheese, apples, and shallots. That reminded me that I could also make a savory Tarte Tatin with blue cheese on top. But I didn’t want to go through the trouble of making the dough for either one. Why not use the apples themselves as a base and put the good things on top?

If the barrels didn't have that bulge in the middle, you couldn't roll them like this.  With or without the hats.  (Photo from octoberfestzinzinnati.com)

If the barrels didn’t have that bulge in the middle, you couldn’t roll them easily like this. With or without the hat. (Photo from otoberfestzinzinnati.com)

So here’s what I came up with — Apples with Blue Cheese, Onions, and Walnuts. You can do every bit of this a day or two ahead, then assemble and put them in the oven. The apples are cut in half, cored, and cooked first, in a skillet. Then you mix the blue cheese, toasted walnuts, and caramelized onion with a little softened butter and spread the mixture on the cut half of the apple. Put the topped apples in a baking dish and bake to heat through.

The dish works well with either beef or pork, or you can serve it on its own either as a starter or after the main course as a salad. And the Tuscanio Rosso is a great pairing because the slight vanilla notes from the oak complement the sweetness of the apple. Some great fall and winter flavors together. And best of all, after posting that video, I’m saving you from the obligatory barrel allusion in the wrap-up!

Bon Appetit!

Tom

Apples with Blue Cheese, Onions, and Walnuts

Serves 4 as a side dish or first course

2 large, firm, apples that are tart and sweet, like Crispin, cut in half from stem to bottom, then cored and trimmed around the stem and bottom end

Unsalted butter

1 cup water or vegetable stock

1 large onion, cut in half, peeled, and each half sliced thinly crosswise

Salt and freshly-ground black pepper

1 teaspoon finely chopped fresh rosemary

1/2 cup (lightly packed) crumbled soft blue cheese

1/4 cup finely chopped walnuts

Heat 2 tablespoons of butter in a large nonstick skillet that has a lid. Add the apples, cut side down, and raise the heat to get the apples going. Cook them this way, uncovered, for 10 minutes, regulating the heat so that the apples get just a little browned on the bottom. Then add the water or vegetable stock to the pan and cover it. When the water starts to boil, reduce the heat to low and let the apples simmer/steam for another 20 minutes. Then start checking them — a sharp knife should go through easily, but the apples should keep their shape. Keep cooking them until they get that way, adding a little water to the pan if necessary. Take the apples out of the pan and put them cut-side up in a small glass or ceramic baking dish and let them cool to just warm.

Meanwhile, melt another tablespoon of butter in a smaller nonstick skillet with a lid. Saute the onion with a pinch of salt for a minute to get it all coated and sizzling. Then put the lid on and cook on low for 15 minutes, stirring occasionally. Remove the lid, stir in the rosemary and some black pepper, and raise the heat. Cook another 5 minutes or so, until the onion is nicely browned. Scrape the onion mixture onto a plate to cool.

In a small bowl, mash the blue cheese with 1 tablespoon of softened butter until very smooth. Stir in the onion mixture and the walnuts. Take one quarter of the mixture at a time and pat it in your hand until it’s flat and will fit on the surface of the apple halves. Place the shaped mixture on an apple half and then do the rest of them.

Bake at 350 degrees F for 20 minutes to heat the apples through, melt the cheese a bit, and toast the walnuts. Serve hot or warm.

To make ahead: Chill the steamed apples in the baking dish covered with plastic, and then microwave them until they’re warm. Refrigerate the caramelized onion, and then microwave it just to bring it up to room temperature. Combine the cheese, butter and walnuts as directed, then proceed with the recipe.

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9 Responses to A barrel of…questions

  1. Evelyn says:

    Thanks for sharing the great information about why oak is used for aging barrels. I plan to wow my friends with it at our next dinner party! Loved seeing the barrel room at the Chateau de Mercures.

  2. Melvin J. Monsen Sr. says:

    Thanks Tom for the information on barrels. Many generations ago, most of Alaska’s Salmon were salted and shipped in barrels weighing approximately 400 lbs. A lot of your information about wine barrels could be applied to the salted salmon barrels. My younger days longshoreing these heavy barrels had escaped my shortened memory. Thanks for bringing it back. Best Regards to You and Cy. Mel Sr.

    • firstvine says:

      Thanks, Mel! I hadn’t thought about the many other food-related uses of barrels. Salted salmon would have many of the same issues as wine, plus the salt is corrosive. Cheers to you and Jilda!

  3. David Ramey says:

    Actually, barrels are currently available made from acacia wood . . .

  4. There is a tradition in Priorat of fermenting and ageing garnacha in small chestnut barrels. The grapes are literally crushed and placed in barrel, where they ferment and evaporate naturally over the course of decades, resulting in an unfortified dessert wine with a nutty character.

    • firstvine says:

      Thanks for the info. I hadn’t heard about the dessert Priorat. But one of my southern Rhône producers told me that her grandparents had used chestnut barrels — but that they were coated on the inside so they were essentially inert.

  5. Sorry, that wasn’t clear: the *juice* is placed in the barrel, not the crushed grapes themselves.

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