7 minute read
VACUUM DISTILLATION SIMPLIFIED
Vacuum distillation is still a rarity in the industry; the vast majority of producers use traditional distillation methods to separate alcohol and other molecules from a water mixture. Whereas high heat is the catalyst to reaction in traditional or simple distillation, vacuum distillation adjusts the atmospheric pressure, lowering it and thus depressing the boiling points of certain elements in the wash.
This can have a number of benefits. For distillation using high temperatures, the time of the process is often extended, the efficiency compromised, and flavor compounds may decompose or be subject to changes. One obvious use of vacuum distillation would be to distill fresh ingredients such as flowers.
Dwayne Bershaw, lecturer of enology at Cornell University, explains that some volatiles can get ‘cooked’ because of the temperatures required to do alcohol distillation at atmospheric pressure. He further explains, “But by lowering that pressure you’re also lowering the boiling temperature of the solution, so hopefully you’re not cooking some really delicate aromatics that you think you might be getting.” It can be difficult to capture the flavors of fresh honeysuckle or lavender, for instance, when you distill those using heat. The high temperature can result in unsavory character from the ingredients cooking, restricting the full availability of potential flavors.
Using vacuum distillation creates the opportunity for a talented distiller to access a different segment of the flavor spectrum. This is important for producers who regularly use fresh ingredients in their distillation. “When I hear about [vacuum distillation], I mostly think of people in the gin production category, stuff like that, where they’re trying to get these really interesting aroma volatiles,” said Bershaw. Many distillers who want to incorporate the flavors of ingredients like cucumber or florals might opt to use extracts, vapor distillation, or maceration, however, each of these methods come with some drawbacks. Instead, a distiller could reach for their tabletop vacuum system, which can distill ethanol at room temperature by reducing the pressure inside the vessel to nearly zero. Once distillation has begun, the ethanol vapor travels through a cooling coil
until it condenses back down into a liquid. This method can be used in tandem with other distilling techniques, such as vapor distillation, to make an elegant and subtle spirit. This tandem approach is popular because of the rarity of having a vacuum still that’s any bigger than a tabletop setup, which could negate any of the efficiency gained by distilling at low temperatures, since the system would have to be recharged so frequently to complete even a modestly sized batch.
The process of vacuum distillation relies on pressure changes to facilitate the distillation, as opposed to heat in atmospheric distillation. Typically, traditional atmospheric distillation takes place between 170 and 200 degrees Fahrenheit; with vacuum distillation, the necessary temperature range changes. At six percent of atmospheric pressure, or 42 mm Hg compared to 760 mm Hg, the temperature at the top of the column only needs to be 68 degrees Fahrenheit, and at the bottom 95 degrees Fahrenheit.
The main draw for distillers to use vacuum distillation is that this process does not “cook” their ingredients. Traditional distillation often will alter the flavor of a fresh or floral ingredient because it’s cooked, which changes the delicate aromas that otherwise exist within that material. While obviously a benefit for gin distillers who are hoping to use this technique, other distilled spirits can be made with vacuum distillation in part or in whole to achieve a radically different profile. Take, for instance, shochu, which is made by both atmospheric and vacuum distillation, depending on the desired aroma and profile. The higher temperature used in traditionally distilled shochu evaporates most of the liquid in the fermented mash; what results is a distillate with a thick, rich flavor and aroma, commonly made from base materials such as barley or sweet potato. Vacuum-distilled shochu has a typical profile and flavor that could be described as mild or concise, compared to its traditionally distilled counterpart.
Another application of this technology would be brandy, or eau de vie. So many of the flavors inherent in the fruit that we distill aren’t able to come over or are lost in the process of traditional distillation. “Whenever I do apple brandy distillation with my students, one of the first really yummy aromas that comes off the still is this really nice high-tone apple note,” said Bershaw. “I think that we’re losing that because I can smell it in the vapor coming out of the still before we’re actually collecting distillate, so it’s probably something that we’re missing because of that.”
Along with the baked or stewed apple, pear, and other fruit flavors that are typically found in brandies, a vacuum-distilled brandy could provide fresh apple and pear notes, which would make for an interesting addition to the flavor spectrum already available. While some traditional cognac or brandy producers will say that not using a traditional still — in fact, not using a direct-fire still with extremely high heat — means that you’re not creating the same chemical makeup necessary for that type of spirit, it seems like consumers could be more adventurous. Seeing the subtle but existing embrace of characterful vodkas or the overwhelming support for smokey, savory mezcal as opposed to the popular tequilas of the past indicates that there is room for new styles of traditional spirit types. The problem, as is often the case when trying to make an innovative and commercially profitable spirit, is educating consumers. There’s already a dearth of comprehensive distilling knowledge amongst casual or even motivated imbibers; to add vacuum distillation on top of a weak foundation would be a difficult task.
Brian Thompson, chief executive officer of Arcane Distilling based in Brooklyn, New York, knows that their approach of making a grain spirit on a vacuum still is unusual and will require an equally novel approach to the marketing of the liquid, but he’s not deterred. Vacuum distillation already exists in the gin world, though it’s not always emphasized; why can’t it become a part of the production of other types of spirit? “The way we really talk about it now is that because the flavors in Arcane are created during the fermentation process, our
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distillation process is really just sort of capturing and preserving that moment in the beer’s life,” he said.
The production process at Arcane almost always seems to zig when you expect it to zag. They make a drinkable beer to start, fermenting it, and then distilling on a vacuum system. Following distillation, their spirit goes through a slight finishing process but they do not age it in the typical sense. “Additional aging would actually be detrimental because those flavors would degrade,” said Thompson. “The real volatile hop aromas especially would sort of disappear.”
Perhaps the most challenging aspect of introducing a vacuum-distilled product into the domestic consumer market would be that the character it creates is often at odds with this country’s preferred style of spirit. There seems to be a notion that all good spirits are full-bodied and heavy with flavor (see: peated whisky, bourbon, or high-ester rums). Some consumers will always assume cask-strength spirit to be not just stronger but of a better quality than its proofeddown alternative. How does a spirit with elegant, unusual flavors, more subtle than strong, perform when the tastebuds of consumers seem calibrated to appreciate high intensity at all times? It will be a slow build, but that’s not to say that appreciation for distilled spirits exists in a vacuum. Perhaps the most challenging aspect of introducing a vacuum-distilled product into the domestic consumer market would be that the character it creates is often at odds with this country’s preferred style of spirit.
Devon Trevathan is the co-founder of Liba Spirits, a nomadic distilling company that focuses on capturing a sense of place in every bottle. She also continues to write about spirits and cocktails, including the science behind distillation and the history of drinks culture. Devon travels constantly these days; if she's not working, she's probably exploring her surroundings in the best way she knows how—her mouth (AKA through food and beverage). You can find her online @devontrevathan or @libaspirits across all platforms.
