Chill filtering is a bit like liposuction—it removes fats and usually isn’t undertaken for health but for cosmetic reasons. Chill filtration is a technical process, executed before bottling, that distillers use to ensure that their spirits stay crystal clear on your shelf. The temperature of a vat of spirit is reduced to 32 degrees Fahrenheit or just below, and the spirit is then run through a filtration system. Chill filtering removes any haziness or “flocking”—the floaty little clouds that can appear in a bottle and that can range from inoffensively wispy to alarmingly phlegmy.
Most spirits naturally have long molecular chains of fatty acids, which can form during fermentation, distillation, and aging. Chilling causes those molecules to coagulate so they can more easily be removed by filters. (Think of putting chicken stock in the fridge overnight, then spooning off the congealed fat the next morning.)
Chill filtration tends to be most important for spirits bottled at less than 86 proof, or 43% alcohol by volume (ABV). Spirits that are higher in alcohol are better at staying crystalline, since they’re able to keep their contents in solution under all storage conditions. With spirits lower than 86 proof, precipitation is more likely to occur and cloudiness can arise, especially if the products are subjected to repeated freezing and warming, as can happen in warehouses and delivery trucks. So chill filtering for lower-proof spirits serves as a defensive measure, helping distillers avoid aggrieved calls from consumers and retailers claiming “something’s wrong” with their bottles.
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It’s also one of those industrial processes that has typically been undertaken behind the scenes, unnoticed and unremarked on by consumers—at least until recently. Now distillers both large and small have begun openly touting their products as “non–chill filtered,” on ads and labels.
For some smaller producers, it’s a sensible way to claim a certain authenticity, while also avoiding the expense of installing an expensive chill filtration system. Yet even larger producers are joining in, at least with select products. “We skipped the chill filtration process,” Fred Noe is quoted as saying in the marketing material for Jim Beam’s Distiller’s Cut. Four Roses also boasts that its Private Selection Single Barrel bottlings are non–chill filtered, essentially echoing the claims of craft distillers such as Leopold Brothers, Chattanooga Whiskey, and Copper & Kings.
It’s become a badge of pride—and has led consumers to wonder, “Should we care?” Does chill filtering actually affect taste?
The answer is yes, no, and maybe.
Crispin Cain is the founder and head distiller at Greenway Distillers in Redwood Valley, California, which produces Low Gap Whiskey in collaboration with Ansley Coale of Craft Distillers in Ukiah. Cain initially resisted using “chill stabilization and filtration,” as he calls it. But he’s come around. “I now see it,” he says, “as a vital link in the chain from the distillation to the glass on your table.”
In part, he’s borrowing from French Cognac tradition, which has been chill filtering for decades. (Cain worked for seven years with Hubert Germain-Robin, who brought Cognac methods to the production of California brandy.) Cain says that because he uses an alembic Charente still, like Cognac producers, his process results in more long-chain fatty acids in the distillate—more modern stills are better at diverting these elements. He chills his spirit in stainless steel tanks to about 20 degrees Fahrenheit, then lets it sit for 10 to 14 days. “When you open the tank on the last day and shine a light into it, there’s a galaxy of coagulated fats,” he says. “And they don’t fall to the bottom but stay suspended.” Not only is the appearance a bit unsightly, but Cain finds that the suspended acids have a bitter taste. Filtration takes care of both.
Joe Corley, a California-based distilling consultant who also made brandy with Germain-Robin, for eight years, says that he generally recommends filtering before bottling, although he makes an exception for older brandies—spirits that have aged 20 or 25 years. After that length of time, many of the long-chain molecules have broken down naturally, and the distillate is less likely to be afflicted with cloudiness. “But with the four- to eight-year-old brandy,” Corley says,” which we were bringing down to 40% ABV, we really had to filter it. The turbidity was ridiculous.”
Corley found that the chief difference between filtered and unfiltered spirit wasn’t so much the taste as the mouthfeel. “There’s a tactile thing,” he says. “The unfiltered was more ‘coaty.’” He played around with different filter sizes and eventually found one that let small-chain molecules through while blocking the haze-inducing long chains. “It was perfect,” he says, “and I didn’t detect any flavor difference before or after.”
Few studies have been carried out on how filtration changes flavor. And side-by-side comparisons are hard to come by for consumers, since most distillers see no reason to offer both filtered and unfiltered versions of the same spirit. A couple of widely disseminated taste experiments, however, approached this question and yielded interesting results.
In 2012, Matthew Fergusson-Stewart, a member of the online malt whisky collective Malt Maniacs, undertook some experiments involving a home chill filtration system (freezer, coffee filters) on four Scotch whiskies that hadn’t previously been filtered. Four whisky fans then sampled them blind; they could distinguish filtered from unfiltered only 46 percent of the time (about as good as predicting coin flips); the majority of the group preferred the taste of the filtered versions.
In 2014 a broader study was carried out by Horst Lüning of Whisky.com, who sent chill filtered (filtered under “laboratory conditions”) and non–chill filtered Scotch samples to a panel of 111 whisky aficionados in Germany. Each panelist then tried to identify which was which, and rated them for quality. Fifty-five percent correctly distinguished chill filtered from non–chill filtered, and preferences were about evenly split—again, not much different from coin flips.
When Maggie Campbell, the head distiller at Privateer Rum in Ipswich, Massachusetts, started her job six years ago, she learned that Privateer’s former distiller had been running the distillery’s product through a tight filter, removing as many of the fatty acids as possible. Campbell switched to a looser filter but within eight months had decided to eliminate filtering altogether.
Campbell says that cloudiness hasn’t been a problem with Privateer’s spirit (some of which is bottled at higher proof), in large part because the distillery follows a careful racking protocol—letting the spirit settle out in the barrel, which is then pumped out rather than dumped, with a small amount left in the bottom. Once several barrels are combined in a vat, it’s left to rack and settle again, then drained carefully so as not to disturb any sediment in the bottom. (About six char-flecked bottles’ worth remains in the vat after racking, which is kept for in-house consumption. (The leftovers “keep developing flavors” after bottling, says Campbell, who quite likes it.)
Campbell has concluded from her experience that flavor can be lost in chill filtering—those long-chain molecules can be a boon, adding richness as well as a rounder mouthfeel. Many consumers might not be able to describe the difference between chill filtered and non-filtered, she says, but “a lot of people could tell something was different.” She also points out that the two tests cited above didn’t duplicate distillery conditions—such as passing distillate through filters at high pressure—which may be why the participants didn’t detect much variation between the filtered and non-filtered spirits.
Regardless of what one can detect on the palate, non–chill filtered spirits are likely to be around for a while. Unprocessed food and drink have hitched themselves to the vague notion of “authenticity,” and authenticity has, for good or ill, become a cultural grail.
“People want authenticity and minimally processed products,” Campbell says, adding that consumers no longer recoil at the sight of lumpy, slightly discolored heirloom apples, for example, and some actually seek them out. “People don’t mind apples that don’t look that good,” Campbell says, “as long as they taste better. That’s a huge change from the 1970s, when every apple looked alike.”
And so it goes with beverages. Educated consumers no longer turn their noses up at hazy beer or cloudy wine—a mysterious murkiness can even make a drink seem more intriguing and inviting. The same may increasingly be said for spirits. A little haze has long been considered a flaw, but tomorrow it may be an asset.
Wayne Curtis is the author of And a Bottle of Rum: A History of the New World in Ten Cocktails and has written frequently about spirits for The Atlantic, Imbibe Magazine, Punch, The Daily Beast, and Garden & Gun, among others.