Froth! The Science of Beer (review)
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Froth! The Science of Beer. By Mark Denny. Baltimore: Johns Hopkins University Press, 2009. Pp. ix+183. $24.95.

The thing to know about Froth! is that it includes a set of differential equations that describe changes over time in "the beer/foam system"—that is, liquid beer and the two distinct types of foam produced by pouring it into a glass—and by no means is that the only math in this lighthearted but not lightweight book. Oh, everything is also explained in lucid prose for those whose calculus is rusty or nonexistent. And Mark Denny does cover topics [End Page 759] that can't be expressed mathematically. Still, this is the cheerful product of a happy complementarity of profession (Denny is a physicist) and avocation. Leafing through the pages one can all but hear the unformed thought: if you can construct a simple mathematical model of yeast population density, even if it might be a little inaccurate for the anaerobic fermentation phase—well, why wouldn't you? Especially since it could be done over beers.

The book begins with a short, idiosyncratic discourse on beer styles and the historical evolution of brewing from prehistory to the industrial macrobrewery (MB), concluding with the rise of the modern microbrewery/ brewpub (µbs naturally). A chapter on how to make good beer at home lets Denny signal where the physics will be coming later, and not so incidentally establishes his bona fides as someone who can actually, you know, brew beer. (Though he skips the recipes, it would be the rare homebrewer who didn't learn a useful thing or two.) Context thus set, Denny proceeds to his true subject. The subtitle takes in a little too much territory—nothing on water chemistry?—but that's in the proper spirit of the thing, and the ground Denny does cover is ample enough: cell population dynamics (those yeast), thermodynamics (what's going on during mashing, boiling, cooling, and fermentation), the behavior of bubbles (that foam), and fluid dynamics (if that can be defined liberally enough to include both dispensing systems and a model of a beer distribution network). Throughout he nods regularly toward how theory is embodied in practice, on both the industrial and craft (homebrewing, or nanobrewing) scales.

Judging by their numbers, popular books on the science of this or that everyday thing constitute a reliably moneymaking genre—presuming it's fair to lump together books that run the gamut from The Botany of Desire to The Science of Star Wars to The Physics of Hockey (another from Johns Hopkins University Press, which evidently has an acquisitions editor with a bent for this kind of thing). It's easier, at least at first blush, to see the likely audience for some of these than for others; then again, not much could have seemed less likely in a midnight beer-league hockey dressing room than a discussion of physics, and yet there it was. Denny's readers will skew toward nanobrewers and frequenters of µbs, among whom there will doubtless be plenty of curiosity about the science of this particular everyday beverage. But anyone with an interest specifically in how traditional craft relates to science-based industry would also find Froth! an entertaining and illuminating case study. [End Page 760]

Joseph Schultz

Joe Schultz brewed his first batch of beer in 1985 and now understands—he thinks—why it took so long for the fermentation to start.

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