What Einstein Kept Under His Hat: Secrets of Science in the Kitchen (6 page)

I’ve always wondered about Kentucky bourbon and Tennessee sour mash whiskey. No other states seem to have a lock on their types of spirits. What sets them apart, and why can’t the same products be made in other states?

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W
hat sets them apart is largely local pride, but virtually identical whiskey can be made anywhere. They just can’t use those state names if they were made, for example, in North Dakota.

First, what is it that makes bourbon bourbon? Bourbon is officially defined by the federal Alcohol and Tobacco Tax and Trade Bureau (TTB), which was split off from the ridiculously conceived Bureau of Alcohol, Tobacco and Firearms (ATF) by the Homeland Security Act of 2002. It is defined as a straight (unblended) whiskey produced at a maximum alcoholic strength of 80 percent by volume from a fermented mash containing at least 51 percent corn, and aged at a maximum alcoholic strength of 62.5 percent in charred, new oak containers. In practice, however, most bourbon whiskeys are distilled to around 60 percent alcohol, and bottled at 40 to 50 percent. And they are made from 65 to 75 percent corn, plus smaller amounts of other grains such as barley, rye, or wheat.

According to the TTB, the word
bourbon
may not be used to describe any distilled spirits produced outside the United States. But no names of states are mentioned in the regulations, except for the perfectly reasonable ruling that a bourbon may not be labeled “Kentucky Bourbon” unless it was made in Kentucky. There are approximately 162 distilleries producing genuine bourbon in the United States. Most of them, but by no means all, are located in Kentucky.

Now what about Jack Daniel’s Tennessee Whiskey? Is it a bourbon? Strictly speaking (and I’d better speak strictly here because tempers run high on this topic), no. It fits all the legal definitions of bourbon—made primarily from corn; aged in charred, new oak barrels; and well within the strength specifications—except for one thing: It undergoes an additional step. After distillation and before aging, it is dripped through a ten-foot-thick layer of sugar-maple charcoal, a process billed by Jack Daniel’s as “charcoal mellowing” but known officially as the Lincoln County Process. That’s the only procedural difference between Jack Daniel’s and most of the anointed and consecrated bourbons.

Jack Daniel’s brags about being a sour mash whiskey, meaning that part of the mash used in the fermentation process consists of the exhausted remains of a previous fermentation. But the sour mash process is used in making almost all bourbons and other whiskeys today, so this fact alone has nothing to do with the Zen of being bourbon.

At a Kentucky Derby Day party, my friends served mint juleps. I noticed that shortly after the host mixed each drink, a coating of frost formed on the outside of the glass. I know that a tall glass of Tom Collins, for example, will get wet on the outside, but I’ve never seen it get cold enough to freeze. What’s special about the mint julep?

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A
sk any dyed-in-the-cotton Southerner and the answer will be “Plenty.”

When sipped at the speed of a Southern drawl on a hot summer’s eve beneath a fragrant, blooming magnolia, few beverages are more refreshing than a mint julep—or more insidiously intoxicating, because its seductive sweetness masks the fact that it is virtually straight bourbon. But also intoxicating (to some of us) is the science behind the frosting.

Stripped to its mundane fundamentals, a mint julep is made by mashing mint leaves with sugar in a metal mug or goblet, filling it with crushed ice, and pouring a generous glug of bourbon in. Now, if we were to add plain water instead of bourbon, the ice and the water would soon come to the same temperature: a temperature at which they could coexist without all the ice melting or all the water freezing. (They would come to
equilibrium
.) That temperature, as you have guessed, is the freezing point of H
2
O, normally 32°F or 0°C.

But bourbon, bless its heart, contains alcohol as well as water. The alcohol (helped by the sugar) lowers the freezing point, just as antifreeze lowers the freezing point of the coolant in your car’s radiator. Because the freezing point is now lower, so is the ice-and-water coexistence temperature, which is the same. If the ice and liquid are still to coexist, they must get down to this lower temperature by melting some of the ice, a process that absorbs heat and makes the mixture colder. It’s the same phenomenon that makes an ice-and-salt mixture so cold that it can freeze cream in an old-fashioned ice cream freezer. The salt in this case lowers the freezing point, as the alcohol does in the julep.

The cooling of the goblet’s contents by the bourbon’s alcohol can be so great that on a humid day the moisture in the air will not only condense on the outside of the goblet but actually freeze there, forming a coating of frost. A Tom Collins won’t get cold enough to freeze the moisture on the outside of its glass because it may contain only a few ice cubes and not enough alcohol to lower the freezing temperature very much. In a julep goblet, however, all that crushed ice has a huge surface area at which the ice/water equilibrium can play out its temperature-lowering game on a grand scale.

For the most spectacular presentation, mint juleps should be made and served in sterling silver—not silver-plated—goblets or cups, rather than in glasses. Glass is a very poor conductor of heat (and cold), whereas sterling silver is 92.5 percent silver, and silver is the best heat conductor of all metals.

A mere Yankee, I dare not venture to present here a recipe for a mint julep, inasmuch as part of the reason the South is warmer than the North is that Southerners are engaged in perpetual heated arguments about the best way to make one. Find a Kentucky colonel (no, not that one; he’s no longer with us) and ask him.

I’ve been having a discussion with some friends about chilling drinks by stirring or shaking with ice cubes—how much ice to use and what the dilution factor would be. One guy said that he uses lots of ice to chill faster and get less dilution. I countered that it may chill faster, but the dilution factor would be the same: less water from each cube, perhaps, but the total amount of melted ice would be the same. Any help greatly appreciated.

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I
’m with the other guy.

First, the colder the ice the better. Colder ice will cool the liquid faster, just as colder rocks would do. And melting is not necessary for cooling; cold rocks would do the job as well.

If two substances are in contact, heat will flow automatically from the warmer one into the cooler one. In this case, heat flows out of the liquid and into the ice. Or, if you will, ice sucks heat out of the liquid. The colder the ice starts out, the more calories of heat it can suck out of the liquid before it reaches its melting/freezing point of 32°F (0°C) and even begins to think about melting. So if the ice is cold enough—far enough below 32°F—there need be little, if any, melting and consequent dilution.

Second, the more ice the better. Lots of ice in the container forces the liquid into crevices between the ice chunks, creating thin layers of liquid that make efficient thermal contact with the ice surfaces and cool faster than would thicker layers of liquid. Another way of putting this is that the more ice chunks there are, the more ice surface is available for heat exchange with the liquid. So again there’s faster cooling and less, if any, melting—if you don’t leave the ice in too long. The best cooling mantra then, is “Lots of ice, short time.”

That’s ice
cubes
, incidentally, not cracked ice. Cracked ice has so much surface area, and the heat exchange between it and the liquid is so efficient, that it will start melting and watering down your drink before you can say Jack Daniel’s.

Unfortunately, most bartenders’ ice isn’t very cold. It has probably been sitting in the bin for hours, warming up to within a few degrees of its melting point, so it doesn’t have much cooling capacity before it begins to melt and dilute your drink.

But luckily, ice doesn’t melt as soon as it gets to its melting point. Each gram of ice needs to absorb another slug of calories—0.080 calories, its
heat of fusion
—in order to break down its solid structure and turn into a fluid. So even not-very-cold ice will still do a pretty good job of cooling, albeit accompanied by some melting and dilution. Just don’t let the bartender stir or (heaven forbid) shake your martini too long.

Because we do want some melting to take place in a martini (the drink will be too harsh unless it contains about 10 percent added water), one must strike the proper balance among the amount of ice, its temperature, and the length of stirring. That’s why so many people mess up martinis, which in principle should be the simplest drink in the world to make.

I’m a moderate drinker. I have a glass of wine with dinner, and in social situations I’ll often have one or two drinks. Really, that’s all. But at holiday-season parties it’s easy to lose track while nibbling and chatting, so on occasion I have imbibed a bit too much for my own comfort and, I fear, for the comfort of others as well. I know everybody’s different, but are there any guidelines for figuring out what effects various amounts of alcohol are likely to have on a person?

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H
aving spent decades on a university campus (no, it didn’t take me that long to graduate; I was on the faculty), I have heard more than a little about what the students call “hearty parties.” Translation: binge drinking.

But the college crowd doesn’t have a monopoly on bingeing, whether deliberate or accidental. For us in the postgraduate population, the occasional holiday-party overdose can be more sinister because we can’t just stagger back to the dorm. In most cases we have to drive home. And while that thought is sobering, the drive, unfortunately, is not.

A 2000 study supported by the National Highway Traffic Safety Administration found that driving performance begins to deteriorate at a blood alcohol concentration of only 0.02, one-fourth the national standard of 0.08 for a Driving Under the Influence (DUI) citation.

So how can we regulate our alcohol intake to reach intoxication stage 1 (relaxation and congeniality) without overshooting to stages 2 (garrulity and diminished inhibition), 3 (poor physical coordination and slurred speech), 4 (lack of control or restraint), 5 (lethargy and stupor), 6 (vertigo), 7 (coma), and 8 (death)?

The discouraging answer is that we can’t. At least not reliably. There are just too many confounding factors. Among the many variables that determine one’s reaction to a given amount of alcohol are genetics, metabolism rate (women’s rates are generally higher than men’s), body weight, and personal alcohol history (heavy drinkers can “hold” more). Overriding all of these factors is how a given amount of alcohol is consumed: whether it is diluted by a mixer, whether it is consumed with or without food, and over how long a period of time it is consumed. The more dilution, the more food, and the longer the imbibing time, the less effect the alcohol will have.

The foremost factor is the total amount of ethyl alcohol consumed. The proverbial plaint “But I only had two drinks” can mean almost anything. In the United Kingdom a standard “drink unit” is any beverage that contains 8 grams of pure alcohol. In the United States a “drink” is taken to mean 12 to 15 grams of pure alcohol, while in Japan it’s 20 grams. But you’ll never see “grams of alcohol” on a beer, wine, or liquor label.

What effects will these amounts of alcohol have on you personally? None, until they get into your bloodstream. That’s why the accepted measure of intoxication level is the blood alcohol concentration, or BAC: the number of grams of alcohol per 100 milliliters of blood. The BAC isn’t measured directly in the blood (except at the autopsy), but it can be measured in the breath because alcohol is transferred from the blood to the breath in the lungs. The concentration of alcohol in the blood has been found to be about 2,100 times its concentration in the breath, so breath testers can be calibrated to read directly in BAC’s.