As I’ve said before, I’m a science geek, and I really love it when I get to read scientific studies about wine. For that reason, I always enjoy reading The Academic Wino, a blog that examines wine studies and summarizes them.
Not quite simply enough for public consumption, maybe, but enough for people like me to decide if I want to look at the study more closely myself. This is handy, because most times it costs hundreds of dollars a year to subscribe to these academic journals, and downloading a single article costs up to $40. So I really appreciate it that these academic winos do some of the up-front work for me.
Today I read a post about a study on the effects of temperature on wine quality during transport and storage. The study authors, in the U.S. and France, first made an artificial wine for testing (because the thousands of compounds in real wine could easily mask the effects the study was examining). They then packaged the bottles with temperature monitors and shipped them to various locations, with travel lasting between one and three weeks. Once the wine arrived, it was chilled to prevent further changes and sampled and subjected to various chemical tests to see how it had changed.
Not surprisingly, The Academic Wino reported that the authors found that significant damage to wine could occur at temperatures recorded during wine shipping based on the temperature reading and testing the contents of the bottles. Not only did the trip at higher-than-ideal temperature encountered in some of the packaging age wines by a year to 18 months in as little as three weeks, but that the highest temperatures aged the wine differently than it would have had it remained at ideal cellar temperature for that year and a half.
This is why most importers and I pay extra for temperature-controlled shipping for our wines, and store them at good temperatures. But I hadn’t seen any studies actually putting numbers like these to the affects of high temperature, and I wondered if there was information there that could be used to look at what happens to wine stored at lots of different temperatures, like you’d find in your home.
So I bought and downloaded the study.* And sure enough, the authors provided data and formulas to calculate what would happen to wine stored at the less extreme temperatures you’d encounter at home.
I decided to pick 77 degrees F, or 25 C, as a temperature you’d find in my kitchen in DC in the summer. Even with the air conditioning on, the sun coming in and the fridge, range, and dishwasher all contribute heat. I then used the data in the study to calculate what could happen to wine stored at that temperature for three months, compared to an ideal cellar temperature of 13 C (55 degrees F). I figured there would be a difference, but I was surprised at how big it was.
The study itself looked at four different effects on wine, and I looked at three of those. Plugging in the numbers to the formulas in the study, here’s what I found:
1) Oxygen uptake. Over time, oxygen diffuses into the bottle through the cork. It reacts with the tannins in red wine and with acids and flavor components in both reds and whites (and rosés too). Some oxygen uptake is absolutely necessary to tame the harshness and astringency of reds and to help whites develop full flavor. But too much and the wine loses its flavor and can become oxidized – smelling and tasting like sherry. It can also create off flavors. This happens naturally over time anyway, but you certainly don’t want to accelerate it unnecessarily.
According to the study numbers I used, keeping wine at 25 C makes wine take up oxygen 8.3 times as quickly as it would at 13 C. This means that wine kept in a summer kitchen for three months would be like wine that had spent more than two years in the cellar. In the case of wine with a lot of tannins that’s meant to be cellared, this might be a good thing because you could drink it more quickly. But many wines are ready to drink once they hit the stores and don’t necessarily keep at optimum condition for more than a few years. And for some older whites, it might put them over the edge of drinkability.
2) Browning. Browning also occurs naturally in wine with exposure to oxygen. You’ve probably seen it in bottles of older wine when you pour them and look at the surface of the wine right at the glass, you can actually see a brown color. It doesn’t mean the wine has spoiled, but it can mean that there’s less flavor and can lead to off flavors as well.
I calculated that storing wine at 25 C makes browning happen 7.2 times faster than at 13 C. This means that three months of summer storage is equivalent to nearly 22 months in the cellar for browning reactions.
3) Ethyl carbamate (EC) formation. Ethyl carbamate forms naturally in wine as it ages. While it doesn’t necessarily affect the flavor, the chemical is classified as a probable human carcinogen, so you’d probably like to avoid it. The study recommends absolutely not storing wine at temperatures above 32 C (90 degrees F) for more than a very short time to prevent rapid EC formation. Because of EC health issues, wineries are actively trying to limit EC formation.
My calculation showed that wine stored at 25 C produces 4.3 times as much EC as wine stored at 13 C. So a wine stored for 3 months at 25 C would contain as much EC as wine cellared for a year at the lower temperature. This isn’t necessarily a problem for anyone’s health, but it is an argument for storing wine at temperatures closer to ideal cellar conditions.
What this tells me is that unless you’re lucky enough to have a basement that keeps wine at a good temperature (which I have, thank goodness), you’ll want to invest in a wine refrigerator if you’re keeping wine around for more than a month or so in DC summer kitchen conditions. If you’re a take it home and drink it kind of person, no worries. But if you plan on storing the wine for more than a few weeks, you might want to think about where you keep it.
Because the study used artificial wine, it’s impossible to know what exactly the data mean for wine flavor. But as I mentioned, it’s likely that many of the chemicals found in wine could have interfered with the measurements done in the study, so they had no choice. I think a follow-up done with expert tasters in a blind tasting would be a great idea. In the meantime, it’s safe to assume that increased oxygen uptake and browning are going to change the taste of the wine, and not necessarily for the better. It’s also possible that the short-term impacts the study authors measured might not apply to longer-term storage, although they don’t specifically say so. So a longer follow-up study wouldn’t hurt either.
In the meantime, though, it seems prudent to take precautions. Obviously, not everyone has the space or budget for a wine fridge, and those people still want to take advantage of good bargains on wine when they find them. In that case, you’ll definitely want to find the coolest place you can for storage. If you have any doubts, buy an instant-read thermometer and test various spots over a number of days when it’s hot outside. Check it a few times each day and keep a record to help you decide where the best conditions are. It sounds like a pain, but it’s worth it to keep your wine in better condition. After all, you do plan to drink it eventually, not just store it!
* Butzke, C.E., Vogt, E.E., and Chacón-Rodríguez, L. 2012. Effects of heat exposure on wine quality during transport and storage. Journal of Wine Research 23(1): 15-25
Luckily, wine stored under the right conditions for a good amount of time can be a thing of beauty. 2005 was an odd year for some wineries in the Southern Rhône Valley. Depending on location, a good number of red wines turned out with higher-than-usual amounts of tannins, which took time to soften up. Over the past year or so I’ve talked with many of our producers about their 2005 vintages and how good they taste these days. 2007 and 2009 were years with more bold fruit flavors, but 2005 has a lovely rich earthiness that’s only now coming through when the tannins soften up. It’s like a door suddenly opens, and there they are.
So while it’s still cool enough to enjoy red wine, try Domaine Chaume-Arnaud Vinsobres 2005 (on sale for $14). It’s a blend of Grenache, Syrah, Carignan, Cinsault, and Mourvedre, aged in concrete tanks without oak before bottling. The wine is biodynamic (even though I can’t put that on the label), and it shows all the care that Valérie Chaume-Arnaud puts into her land and winemaking. Like the feeling of a warm blanket on a chilly night, it also tastes amazing going down.
Although I gave you a recipe with mushrooms in it last time, mushrooms (along with eggplant and lamb) are a perfect accompaniment to wines from Vinsobres. This gratin of mushrooms and onions is great hot, warm, or at room temperature. Spread the gratin on thin slices of baguette and serve as an appetizer, or on top of a salad for a simple main course. The allspice picks up the spice in the wine and the combination just sings. (I’ll leave it to you to decide which tune!)
Serves 8 as appetizer, 4 as main course over salad
4 moderately large yellow onions (2 pounds)
1 pound crimini mushrooms
½ pound shiitake mushrooms
3 tablespoons butter (plus more for the dish)
1 tablespoon olive oil
½ teaspoon ground allspice
1 teaspoon each fresh thyme and rosemary, chopped
Salt and freshly-ground black pepper
¼ cup heavy cream
½ cup grated Parmesan cheese
1/3 cup grated Gruyere cheese
1 baguette, sliced a half-inch thick, slices toasted if you’d like
Peel the onions, cut them in half through the poles, then slice each half crosswise into thin slices. Heat 2 tablespoons of the butter in a large nonstick skillet with a lid over medium heat, add the onions along with some salt and pepper, and the allspice, thyme, and rosemary. Stir to coat. When everything sizzles, cover the pan, turn down the heat to low, and let the onions cook for 15 minutes. Remove the lid and raise the heat to medium. Continue to cook the onions until they just start to brown, stirring occasionally. Spoon the onions into a bowl and set aside.
While the onions are cooking, prep the mushrooms: wipe them all with a barely damp paper towel to clean them. Cut off the end of the stem of the criminis, and slice them fairly thick. Remove the shiitake stems and slice the caps the same way. Once the onions are cooked, heat the remaining butter with the olive oil in the skillet. When it stops foaming, watch until the mixture heats a bit more, just barely shimmering. Add the mushrooms and spread them out quickly. Raise the heat to medium-high and cook the mushrooms, without stirring, until they brown on the bottom. This will take a minute or two. Put on the lid and lower the heat to medium. Cook for two minutes, the remove the lid. Put the onions back in the pan, mix everything up, then turn up the heat. Cook the mixture, stirring, until the liquid is almost evaporated. Taste for salt and pepper. You don’t want too much salt, since the cheese is also salty.
While the mushrooms are cooking, place an oven rack about six inches under the broiler, and preheat the broiler. Butter a shallow baking dish (a shallow 13 x 9 – inch dish works well), then spoon in the cooked onion/mushroom mixture. In a small bowl, beat the egg yolks and cream with a pinch of ground pepper. Beat in the grated cheeses. Spread the topping over the onions and mushrooms, then put it all under the broiler for a minute or so, until it’s nice and golden. Let it sit for five minutes, then serve on the baguette slices.