Health & Medicine / Nutrition

Ayu, or sweetfish, is a freshwater species that lives
on algae and moss, which give its flesh a watermelon
scent. Salt-grilled sweetfish is considered one of
Japan’s tastiest foods. Each fish typically grows to
about six inches.

At 6 a.m. workers are inspecting shipments of gleaming ice-packed fish at IMP Foods, a company in San Mateo, California, that supplies sushi-grade specimens to Japanese restaurants and a coterie of some of the most famous—and famously picky—American chefs. Harold McGee is in his element. “Look at that, with that schnoz, and a whip coming out of its tail,” he says, stooping over what turns out to be a cornetfish, a long, bony creature with a fluted tube for a snout, a strange rear end, and an altogether alarming red color. “In Japan we call it aka-yagara, which means ‘red arrow,’” says Glenn Sakata, IMP’s general manager. “It makes wonderful broth.”

A golden threadfin bream, itoyori in Japanese, also catches McGee’s eye. Favored for sashimi, it’s quite lovely, with silver skin, luminous yellow stripes, a tail that blushes deep pink. Sakata mentions in passing that both fish are bought by the French Laundry, Thomas Keller’s four-star temple to cuisine in Napa Valley. The sea bream shimmers with freshness in its box of shaved ice. McGee, who is wearing a regulation-issue hairnet, bows over it and draws a deep, appreciative breath.

McGee is the author of On Food and Cooking: The Science and Lore of the Kitchen, a doorstop of a book that first appeared in 1984 and became an instant classic. Tall, bearded, and unapologetically bookish, he’s America’s premier food wonk. He likes nothing better than surfing journals the likes of Cereal Chemistry, Poultry Science, and The Bulletin of the Japanese Society of Scientific Fisheries. In fact, he’s made a career of turning huge amounts of arcane food science, centuries of history and culture, and wonderfully oddball, just-for-the-heck-of-it facts into a good read for curious cooks and eaters. Somehow he seems uniquely up to the task. How many people have studied both physics and English literature at Caltech, earning a hybrid bachelor of science degree in literature? McGee has become the go-to guy for such questions as: How much oil can mayonnaise absorb? Why do red beans cause gas? How do you deal with an overdose of wasabi? When it came to fish, though, the original On Food and Cooking had little to say. Back then, meat research meant red meat. Fish barely got a mention.

Twenty years later, “there’s been an explosion of information on the subject,” McGee says. Fishing has become “a more important and visible industry.” Fish stocks worldwide are under pressure as never before, “so national governments put more resources into research because of problems with sustainability and developing aquaculture.” Seafood consumption, meanwhile, is rising, driven in part by health concerns and America’s love affair with sushi. Sales of sushi in the United States have been booming, says Sakata. Now we’re buying tuna rolls in supermarkets.

So McGee’s new On Food and Cooking, 10 years in the making and almost twice the heft of the original, now includes an entire section on fish.

Fish, especially ocean fish, as McGee points out in his new book, live in a very different world from ours and that of the other animals we eat. The rules are different from those for cattle, pigs, and chickens. To understand the character of fish as food—what makes it taste and smell the way it does, why you like it, and why you sometimes don’t—you must bear in mind the adaptations fish have made to life in water. Also, judging from McGee’s example, you have to follow your schnoz.

As you step through the door into the cool sanctuary of IMP’s fish market, there’s a slight briny edge to the air that instantly recalls the seaside. “Seacoast smell,” announces McGee. It’s the smell of bromophenols synthesized by algae from the bromine in seawater. In coastal areas, these bromophenols are propelled into the air by the action of waves. “Think of waves dashed on rocks,” says McGee. Ocean fish accumulate the phenols in their tissues by eating algae or other algae eaters. A nice fresh fish is never smelly or “fishy,” says McGee. But its bromophenols can magically conjure up sea air.