Whisky consists primarily of water and alcohol. The rest (<1%) are flavour substances and aromas. When we speak of alcohol in the context of food, we always mean ethyl alcohol, or ethanol for short. The chemical formula is C2H5OH. This mixture doesn't behave like pure water but also not like pure alcohol. The following article tries to illustrate the physical peculiarities of Whisky. Show Whisky producers take special care that no methyl alcohol (methanol, CH3OH) gets into the final product. The yeasts are bred in such a way that they don't produce methanol. Cutting off the foreshots during distillation provides double safety. In the chart above is the ethanol molecule. The carbon atoms (C) are black, the oxygen atom (O) is red and the hydrogen atoms (H) are grey. To the right of the ethanol molecule you can see a water molecule (H2O). A closer examination reveals that, except for the oxygen atom, the ethanol molecule is symmetrical to a perpendicular plane between the carbon atoms. Only one hydrogen atom has been replaced by an oxygen-hydrogen group (-OH group). In the sum total, the ethanol molecule is electrically neutral, but the -OH group causes local differences in electronegativity (so-called dipoles d+, d-). Normal water molecules have these dipoles, too, since they're also angled (109°). These dipoles on the ethanol and water molecules cause the formation of hydrogen bonds between the molecules. Hydrogen Bonds Between Water and Ethanol
September 9, 2019
Whiskey enthusiasts who get the chance to taste-test with a master distiller may notice that at some point he’ll add some water to the glass. Doing so is said to open up the flavors and aroma of the drink. Even the word “whiskey” stems from the Gaelic word “uisge,” meaning “water.” But why is the water so important? Scientists say water improves the taste because alcohol molecules and those that determine the whiskey’s flavor stick together. So if wine pairs well with cheese, then whiskey pairs well with water. And the reason starts with how whiskey is made. How whiskey is made: three ingredients are neededJust three ingredients are needed to make whiskey: water, barley (or other types of grain) and yeast. The kind of grain used varies with the different types of whiskey being made, but all whiskeys need a small amount of malted barley to begin the fermentation process. The water you use for whiskey is often considered the most important factor in making a good whiskey. Clean, clear and free of bad-tasting impurities like iron are the driving factors in selecting water for whiskey. Kentucky, as well as Maryland, Pennsylvania and Indiana, is an area rich with limestone so water there contains carbonates, which can alter the flavor. Scottish water, known for making fine whiskey, is famous for mysterious reasons. Because of the importance of water in how whiskey is made, a large number of distilleries are located next to a river or lake. The whiskey manufacturing process: five stepsBeyond ingredients, the manufacturing process for whiskey typically involves just five steps: Malting the grain. All grains, with the exception of barley are ground into meal in a gristmill. The meal is mixed with water and cooked to break down the cellulose walls that contain starch granules. The first step of malting barley is to soak it in water until it’s saturated. It gets spread out and sprinkled with water for about three weeks until it begins to sprout. Germination produces an enzyme named amylase, which is responsible for converting the barley into sugars. The next step involves drying the barley with hot air from a kiln. The fuel used to make Scotch whisky includes peat (carbon-rich substance made when plant matter decomposes in water), which gives it the characteristic smoky flavor. Malted barley is then ground like other grains. Mashing. Mashing is when you mix cooked grain with malted barley and warm water. The amylase converts the starch into sugars. After several hours of mashing you get a thick, sugar-rich liquid known as mash. Fermenting. Once the mash has cooled, it’s transferred into large tanks (or fermentation vessels) to begin the fermenting process. These can be closed (Scotland) or open (United States). Yeast is added and turns the sugars present into alcohol. Fermentation usually takes about 48 hours, however, some distilleries will let it go longer in order to create differing taste characteristics. The remaining liquid contains between 5-10 percent ABV and could be made into beer. With beer, the next step would be to brew the liquid, while whiskey is distilled. Distilling. Scotch whisky is distilled in traditional copper pot stills. Modern distilleries often use a continuous still. There’s a tall cylindrical column with perforated plates. Steam enters the still from the bottom and the distiller’s beer enters from the top. The beer is distilled by slowly dripping through the plates, and alcohol is condensed back into a liquid. The initial distilling produces “low wine,” which is unusable in its current state. It gets distilled a second (or more, depending on the type) time to produce “high wine” or new whiskey which is 70 percent alcohol. The temperature at which the liquid is distilled determines the proportions of water, alcohol and congeners. A product with 95 percent alcohol will have no flavor because it has no congeners. Too many congeners will also taste bad. Before whiskey is finalized, distillers will remove bad-tasting congeners by either boiling them off or if they’re light and floating on the surface of the liquid they can be poured off. The high wine in Tennessee whiskey is filtered through charcoal that has been produced from burning wood from sugar maples before it is aged. The filtration removes unwanted congeners and the result is a very smooth whiskey. Aging. Once again, water is a key ingredient in the rest of the manufacturing process. After the high wine is distilled, water is added to reduce the alcohol content down to either 50-60 percent for American whiskeys or 65 percent or higher for Scotch whiskies. American whiskeys are aged in warmer, drier conditions so they lose water and increase alcohol content. Scotch whiskies are aged in cool, wet conditions so they absorb water and become less alcoholic. Whiskey is then aged in wooden barrels, typically made from charred white oak. White oak is the preferred wood because it can hold a liquid without leaking and it also allows the water to move back and forth within the pores of the wood, adding flavor to the whiskey. Maturation for whiskey takes at least two to four years but many whiskeys are aged for 10 or 15 years. During each year of maturation, about 2 percent of the spirit is lost as a result of natural evaporation. This is called the “angel’s share” and explains why older whiskeys are less common and much more expensive to buy: there’s less whiskey in the cask to bottle. Glass bottles are always used for whiskey because the liquid does not react to the glass or change its flavor. Three factors of the aging process that change the flavorAlthough aging whiskey is complex, there are at least three factors that change the flavor. Enter: water. Before whiskey is bottled, water is added to dilute it to about 40 percent alcohol by volume. The mixture of water, alcohol and congeners react with each other over time. These ingredients then react with oxygen in the outside air through oxidation. The final factor is that water absorbs substances from the wood as it moves within it. And even though whiskeys are already diluted below 45 percent ethanol (alcohol), adding a few drops of water to your glass to dilute it even more can help the overall flavor by encouraging the other chemicals to evaporate, enhance the aromas and produce a whiff of flavor each time you take a drink. As with everything in life, too much of a good thing can be detrimental. But when it comes to whiskey, water is the main character. Rackhouse Whiskey Club scours the U.S. looking for the best distilleries with the most interesting stories to curate a unique subscription box filled with full-sized bottles of hard-to-find small batch whiskey. We’re building a community of premium craft whiskey drinkers. And you’re invited! Join us! Classy whiskey drinkers like to add a few drops of water to their glass. Now chemists have explained why that makes it taste better. Whiskeys and other liquors start out as sugary slurries. Yeast eat the sugar and make alcohol. Distillers heat up that alcoholic mixture, isolating ethanol (the alcohol that gets us drunk) along with some of the molecules that give whiskeys their taste and smell. Unlike vodka, whiskeys are aged, often in oak barrels, which add even more flavor compounds. At that point, the whiskey is somewhere between 55% and 65% ethanol, water making up most the rest. Most whiskey makers will add more water to bring the ethanol concentration down to 40%—80 proof in liquor lingo. But the popularity of undiluted whiskeys, often labeled ‘cask strength’ is on the rise. Here comes chemistry to tell you why water makes your whiskey better. Water and ethanol are close enough chemically that they mix together completely—you’ll never find an old bottle of whiskey that’s separated into alcohol and water layers. But they’re not identical, and advanced imaging technology has shown that water and ethanol molecules tend to cluster unevenly within the mixture. Chemists Bjorn Karlsson and Ran Friedman at Linnaeus University in Sweden went a step further. Using computer simulations, they modeled the interactions between molecules of water, ethanol, and guaiacol, which helps make the smoky flavor of scotch and other whiskeys. They found that guaiacol gets concentrated near the surface of your whiskey when ethanol concentrations are below about 45%. At higher proofs, guaiacol mixes down into the glass, depriving your nose of a good hit of that smoky flavor. Karlsson and Friedman describe their work in Scientific Reports. From their simulations, the researchers found that ethanol molecules tend to concentrate at whiskey’s surface. An ethanol molecule has two halves; on one end, an oxygen atom bound to a hydrogen atom, and on the other, two carbon atoms surrounded by hydrogen atoms. The former is almost identical chemically to water and mixes with it easily. But the latter is more like an oil. Those oily halves are mostly found at the surface, with as little contact with water molecules as possible. Guaiacol also has on oxygen-hydrogen end and an oilier end. Both ends are weakly attracted to ethanol. At low proof, ethanol molecules have more freedom to congregate at the surface, pulling guaiacol along with them. But at higher proof, there are more ethanol molecules in the rest of the glass. They cluster around the guaiacol molecules, pulling them away from the surface. And while the researchers only modeled guaiacol’s interactions, they have reason to think other whiskey flavor molecules act similarly. Because other major components of whiskeys’ aroma like cresols (tar smell), eugenol (spicy smell) and vanillin (obvious) are in the same chemical family as guaiacol, Karlsson and Friedman speculate the same rules of dilution likely apply. So while you might think drinking cask strength whiskey makes you look cool and tough and authentic, you’re probably missing out on the flavors that make whiskey drinking worth it. And even though most commercial whiskeys are already diluted below 45% ethanol, the researchers found that further dilution—say, a few drops of water in your glass—can help even more. Between whiskey with 45% ethanol and 27% ethanol, the attractions between guaiacol and ethanol molecules dropped by half. That makes it easier for guaiacol to shuffle off its molecular coil and evaporate. Once it’s airborne, you get an even stronger flavor punch each time you raise that whiskey glass to your mouth. Drink more water. It's good for you. |