American Scientist

LIQUID INTELLIGENCE: The Art and Science of the Perfect Cocktail. Dave Arnold. 416 pp. W. W. Norton, 2014. $35.00.

When I opened it, I thought I knew what to expect from Liquid Intelligence: a glamorous coffee-table book with a smattering of vague science, then page after page of slick photos and cocktail recipes. Turns out, I was half right. The book is indeed sleek and stunning. About the science, I couldn’t have been more wrong. “Think like a scientist and you will make better drinks,” author Dan Arnold writes in the introduction. Then he spends the next 400 pages telling—and showing, through a wealth of photos—precisely how. Selecting a recipe to include alongside this review proved tricky, in fact, because so much detail accompanies each one, information that builds on itself methodically throughout the book. (Arnold includes nine pages on how to make ice properly!) Liquid Intelligence will open your eyes to what’s possible in crafting a cocktail, always with the goal of making the very best drink.

Although obsessive might be one way to describe Arnold, I quickly came to respect his expertise on all things related to both professional and home bartending. Arnold founded the culinary technology department at the French Culinary Institute and now co-owns a high-tech cocktail bar and affiliated innovation workshop; his approach blends creative experimentation with a dogged focus on quality and consistency. He begins by introducing the equipment needed for making drinks, pointing out the benefits and drawbacks of each available tool. For example, a narrower jigger is better for accurate measuring than a wide one, and a jigger with straight sides is more accurate than a conical one. (In each case, the volume involved in a measurement error is less.) Not surprisingly, a laboratory-style graduated cylinder works best of all. He also explains that a glass shaker affects drink temperature more than a metal one due to its higher specific heat: The glass shaker will transfer more heat—whether to or from the drink—as it comes to an equilibrium temperature. To standardize the fruit juice at his own bar, Arnold uses a refractometer to measure the sugar concentration, which can change overnight.

As he digs further into the topic of flavor, Arnold discusses how different sugar molecules change with temperature and how these changes in turn affect the taste. He describes the flavors of various food acids, like lemony citric acid and sour-grape tartaric acid, and explains that pH paper is useless in a bar for measuring the acidity of such ingredients as lime juice or champagne, because, as Arnold explains, “your tongue doesn’t work like a pH meter”: The taste of an acid is based not on the number of free hydrogen ions but on the titratable acidity—in other words, the number of acid molecules present. And he shares food chemistry tricks he has picked up over the years. For instance, he points out that a pinch of salt makes almost any cocktail taste better, especially if the drink contains fruit, coffee, or chocolate.

Although Arnold writes from the perspective of a seasoned professional, he is conscientious about what is possible at the average home bar, instructing readers on the best techniques and equipment as well as the affordable, good-enough options. The cocky voice from the introduction grew on me; ultimately, I found the irreverent tone entertaining. (For example, at one point he advises readers to “violently smash the hell out of the lime,” and to “forget hand reamers; they suck.”)

The book contains a mind-boggling amount of information about the physics and chemistry at work in seemingly simple mixed drinks. In the section on ice, Arnold describes how clear ice forms on lakes (from one starting point, pushing impurities out) and how ice made mechanically freezes too fast, forming multiple crystals in different locations and trapping impurities. Ice cube trays hinder expansion, he explains, causing the ice to bulge and fracture. This makes for cloudy ice that tends to shatter, producing ugly cocktails that become watered-down when shaken. Bartenders can make clear ice with a machine that freezes water from one side, or they can use a cheap workaround: Fill a cooler (the typical beach cooler will do) with hot water and let it degas and cool without stirring. Then put the whole thing into the freezer; the water will freeze from one side, forming clear ice, with the impurities ending up at the bottom. This clear ice can easily be cut into smaller cubes.

Arnold turns to science to improve every detail of his cocktails. For example, when muddling basil, he noticed that it immediately began to brown. Muddling, which involves crushing an ingredient to release additional flavor, is usually done with a handheld mashing tool. The broken basil leaves contain enzymes that promote oxidation, causing browning and off flavors. The enzymes can be stopped, however, with alcohol. So Arnold invented blender muddling, in which he purees the basil leaves into a small amount of liquor so quickly that the enzymes cannot act. He also uses nitro muddling, instantaneously freezing the basil in liquid nitrogen, then crumbling the brittle result. Both techniques yield bright green muddled basil with superior flavor. You can try it yourself in the Thai Basil Daiquiri recipe included above.

Whether you own a bar, enjoy cocktails at home, or just want to be fascinated, Liquid Intelligence will teach you more than you thought possible about the world of cocktails. Furthermore, the book seems poised to find its way into the hands of many eager learners. After I submitted this review, news broke that Dave Arnold’s work had netted the 2015 James Beard Foundation Book Award in the beverage category. With any luck, Arnold-inspired drinks may be debuting at bars and cocktail parties near you.