We get this question so often in the tasting room that this article in the San Francisco Chronicle by Janet Fletcher recently caught my eye ..........
My nightly dinner partner and I have no trouble finishing a bottle of wine, but sometimes I have to dine alone. I still want my half bottle, or a little less or a little more, but that creates the leftover dilemma. What's the best way to store a partial bottle of wine so that it hangs in there for a few more days?
My husband and I have long had an inexpensive, low-tech solution that we believed was the best possible option. But all the ads in wine magazines for vacuum devices and inert-gas-dispensing canisters made me wonder if our leftovers would enjoy longer lives if we invested in one of these much-touted tools.
What to do with the remains of a bottle is a persistent dilemma for the single diner, or the couple who may drink only one glass each per night. The 750-ml bottle may be the perfect size for two people enjoying a leisurely dinner at home, but it's too much wine for many situations. And even novice wine drinkers can tell that the glass of Pinot Noir they enjoyed from a fresh bottle rarely tastes as good when poured from a partial bottle several days later.
Air alters wine in a couple of major ways, says Andrew Waterhouse, a professor of enology at the University of California at Davis who has studied the chemistry of wine oxidation. Twenty percent of air is oxygen, and oxygen is the real troublemaker in a partial bottle. Acetobacter, the bacteria that can turn wine into vinegar, remain harmless unless oxygen is present. Then the bacteria swing into action, converting alcohol into acetic acid and producing an aroma Waterhouse calls that "hint of salad dressing." Depending on the amount of available oxygen, an opened wine can start exhibiting eau de vinaigrette in three to five days.
Oxygen is also the instigator of oxidation, the process that can eventually make a fresh white wine smell like sherry. An unopened bottle of Chardonnay in a cellar may take 10 or 15 years to get to that point, the result of oxygen slowly seeping past the cork. A half-empty bottle of Chardonnay, even if recorked and refrigerated, may show oxidation in a matter of days.
That's why all the devices claiming to extend the life of an opened wine aim to minimize the wine's exposure to oxygen. Some, like Private Preserve, fill the empty space, known as the headspace, with an inert gas such as argon or an argon-nitrogen blend. These gases or gas blends are heavier than air, so they sink below it and push the air out, in theory. Nitrogen is too light to use alone, argon too costly and carbon dioxide - heavier than argon - can impart a perceptible spritz. Consequently, manufacturers usually blend gases. Private Preserve uses a mixture of all three gases, keeping carbon dioxide below the perceptible level.
Vacuum devices like Vacu Vin and the Metrokane vacuum decanter theoretically pump out enough air to slow oxidation. Restaurants and wine bars have another option that is too costly for home use: the Cruvinet- or WineKeeper-type systems that dispense wine using a tap while instantly replacing the dispensed wine with nitrogen.
At Cav, the popular San Francisco wine bar, owner Pamela Busch says she uses an industrial argon tank to preserve partial bottles. "At the end of the night, we take all the (open) bottles, line them up and spray gas into them," says Busch. "It works better than anything out there."
Bacar, the San Francisco restaurant with a large wine-by-the-glass list, uses a similar procedure, says wine director Mickey Clevenger. The bartenders don't gas dessert wines, which oxidize slowly. Nor do they gas sparkling wines, which are protected from air by the escaping carbon dioxide. But they gas everything else, red and white. The following day, the wine staff tastes each gassed bottle to make sure it is up to par. "We do have to pour a lot down the drain," admits Clevenger, who says he can sometimes perceive an off smell. "To be honest, it's probably like half of them."
One thing that perplexed me, when I began experimenting with Private Preserve, is how to know when I had added enough gas. You can't see the product go in or the air come out, so you can only guess at the right dose. The simple instructions specify one long burst followed by four short ones, but it seemed to me that the amount should vary with the level of wine in the bottle.
"You gotta trust me," said Scott Farmer, the Napa entrepreneur who created Private Preserve 20 years ago. "If you follow the directions, you will get the results."
Farmer acknowledged that a mostly empty bottle would need more gas than a mostly full one, but said he believed his customers intuitively grasped that. No one would buy the product if the instructions were complicated, he argued.
I asked Clevenger at Bacar how he knew he had added enough gas to displace the air. "You just go pffffft, and that's what you do," he said. "You listen, and the next day you taste."
Our method at home, instituted by my winemaker husband, is to simply decant any leftover wine into a smaller clean bottle, preferably filled to the top to eliminate headspace. We keep an assortment of 375-ml half bottles, 187-ml quarter bottles (the size airline wine comes in) and even smaller bottles purchased from a lab supply company. By minimizing headspace - essentially mimicking how the wine was stored to begin with - we have done the best we can for the wine, in his view.
A related method, which wine writer Dan Berger favors, is to add glass marbles to a partial bottle until the wine reaches the top, thus displacing the air with glass.
"That'll work," confirms Waterhouse. "In fact, people do that in the lab, but I think it's kind of a pain."
Most of the wine professionals I spoke with preferred the inert-gas method over the vacuum devices, based on their experience or habit or convenience. But I wondered whether any of these methods, including my decanting procedure, had more scientific support.
"The skeptic would normally say, 'Show me some data,' " says Roger Boulton, a professor of enology and chemical engineering at Davis. "And guess what? You can't find any." Faith in any of these procedures is "based on claims rather than any evidence of performance."
Vacuum devices will indeed remove some of the air from the headspace, scientists agree. But dissolved oxygen remains in the wine - the oxygen that entered when the bottle was opened and poured. When you pump air out of a bottle with a device like the Vacu Vin, you lower the air pressure in the headspace. The pressure differential causes oxygen and esters - volatile compounds responsible for the aromas in wine - to come out of solution and enter the headspace to create equilibrium. So while a vacuum reduces the amount of oxygen in the wine, more than enough remains to cause oxidation, says Boulton. Worse, in some views, you lose aromas to the headspace.
As for the inert-gas spray cans, they're just not thorough, says Waterhouse. "You'd have to use most of the can to get most of the air out of the bottle," he says. If you use the cans as directed, "you're just diluting the oxygen."
My method of decanting leftover wine into a smaller bottle introduces more oxygen, which isn't good, the scientists say, but by filling the bottle to the top, I'm minimizing aroma loss. Since oxidation occurs gradually and I typically finish the wine in the next two or three days, I think that's a smart trade-off.
"Pour the wine very carefully down the side," advises Richard Vine, a professor in the food science department at Purdue University and the author of many texts on winemaking. "Once you've reached the level where the cork can actually touch the wine, I think that's the best you can do. But as far as I'm concerned, it's still not going to be the same. Once you pull that cork, the wine's going to be different."
Vine says that he and his wife long ago decided that no preservation methods repaid the effort. Any bottle they don't finish one evening, they use in cooking over the next few days.
Peter Marks, senior vice president of wine at Copia, the American Center for Wine, Food & the Arts, and a Master of Wine, says he is not so finicky. He uses Private Preserve at work, but at home he doesn't bother, especially for a red wine he expects to finish the next day.
"Sometimes wine actually improves," says Marks. "I've got three Chiantis on the counter, and there's one bottle that seems to get better every day." The oxygen can soften tannins and allow funky smells to dissipate, which is one reason why winemakers routinely rack red wines, transferring them from one barrel to another.
At Clos du Val, the Napa winery, hospitality manager Leah Trefry says she doesn't gas or otherwise try to protect open bottles of red wine overnight. "The wines want the oxygen," says Trefry. "They're not as tight the next day. If a wine can't hold overnight, it's not a wine that's going to be able to age." Any partial bottles of white wine are simply refrigerated.
Refrigeration does slow oxidation, so most experts recommend chilling leftover white wine, at least. Marks says he will sometimes put an open red wine in the fridge, too. But refrigeration isn't entirely benign, as the colder the wine, the more soluble the oxygen, making it easier for the gas to be dissolved into wine. Still, suggests Boulton, refrigerating whites and keeping reds in a cool cellar is better than leaving them at room temperature.
Ronn Wiegand, a Napa wine consultant and legendary taster who holds both Master of Wine and Master Sommelier titles, takes chilling a step further.
"I've frozen probably 20,000 bottles," says Wiegand, who has been freezing partial bottles to preserve them since the late 1970s. "We bought a stand-alone freezer just for wine." The bottles must be frozen standing up to prevent the alcohol, which doesn't freeze, from dissolving the cork.
Wiegand knows that oxygen is far more soluble at such low temperatures, but he also believes that freezing brings oxidation to a crawl. "Let's be very frank about this," says the wine expert. "They find prehistoric animals in glaciers that have barely rotted in a million years. You should just apply that same sort of principle."
Young wines in particular do well in the freezer for up to a year, says Wiegand.
With some young red wines, quality even improves. "It knocks some of the tannins out of them," Wiegand says. "The wines soften and the fruit shows a bit more. I have on many occasions said, 'I bet this wine would be a lot better after I freeze it.' "
He resuscitates his icy wines with three to four minutes in a microwave, three to four hours at room temperature, or half an hour in a warm-water bath. "All these methods are totally acceptable, and nobody can tell the difference," claims Wiegand. Freezing does cause tartrates to precipitate, even in cold-stabilized white wines, but that doesn't affect quality, he says
"Oh, no, " said Vine, laughing, when I told him about Wiegand's freezing method.
"Cryogenic wine treatment changes the molecular structure of wine, much like freezing food. There are a whole lot of dynamics going on there." Whether freezing solid food is comparable to freezing a liquid such as wine is disputable, but Wiegand's method clearly makes some people uncomfortable.
At least options do abound for consumers who want to make wine leftovers last. What's missing is consensus on the best practice. But whatever preservation method you choose, don't try it on older vintages - say, wines 10 years old or more. Be prepared to open and drink these bottles in one sitting. They almost never last until the next day, no matter what precautions you take, as they are already far down the path of oxidation. Another slug of oxygen tends to put these wines over the edge.
For Boulton, the Davis scientist, no wine preservation method is any better than another without data to prove it. "Where's the independent lab analysis?" he says. "Any of these groups should be able to do that and present their data." Without the numbers, says Boulton, "you've got to be a skeptic."
Preservation methods
Vacuum preservation
-- Pro: pump out air, theoretically slowing oxidation
-- Con: loss of esters, wine's aromatic compounds
Inert-gas preservation
-- Pro: easy to use; displaces some air, theoretically slowing oxidation
-- Con: consumer devices merely dilute the oxygen; they don't completely remove it, so oxidation potential remains
Decanting into smaller bottles
-- Pro: minimizes headspace; low cost
-- Con: decanting introduces oxygen
Freezing
-- Pro: easy and inexpensive; dramatically slows oxidation
-- Con: inconvenient; precipitates tartrate crystals; extreme cold makes oxygen more soluble
Displacement with marbles
-- Pro: inexpensive; does not introduce oxygen
-- Con: tedious; must keep marbles clean; subject to ridicule; some oxygen remains in wine
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