The Story of Sushi (15 page)

“E
verybody ready to get fishy today?!” Zoran yelled the next morning. “From here on out, fishy, fishy, fishy!” He had an evil grin on his face. “You’re going to need to know the Japanese names for every single part of the fish,” he said. He peered down the table. “And Takumi, you’ll have to know the English names.” Zoran went on. “If the sushi chef says to you, ‘
S
ji sakana,
’ he means clean up the fish. Not fillet. Just clean up. Take out the gills, the guts.”

More guts? Kate steeled herself. This time she didn’t want Zoran telling her that she “hadn’t prepared her fish properly.” She was sick of being the class flake.

Zoran drew the outline of a fish on the whiteboard. He labeled all the fish parts on the diagram with their Japanese names. The students scribbled furiously in their notebooks. Zoran set out a cardboard box on the table with a thud. Mackerel again.

“
Saba!
Today, we are going to make
saba
sushi—and sashimi.”

In the old capital of Kyoto, mackerel was one of the most common fish used in early Japanese sushi, back when chefs pressed entire fillets of fish onto sushi rice in boxes with heavy stones. But mackerel was never used raw for sushi. Nor was it used cooked.

“We usually marinate it with salt and vinegar,” Zoran said. “The thing you should know about
saba
is that it’s susceptible to parasites.”

Mackerel is perilous to serve raw. Mackerel is so difficult to keep fresh that Japanese chefs sometimes call it the fish that “spoils even while still alive.” Humans can also pick up more than fifty different parasites from eating raw or undercooked fish; removal of parasites can require surgery. A worm called anisakis is one of the most prevalent parasites, and its larvae love living inside mackerel.

The clever larvae of anisakis swim around looking delicious. They
want
to be eaten, and usually a small crustacean will oblige. The larvae live happily in the stomach of the shrimp or krill until a mackerel comes along and eats the crustacean. Then the larvae burrow into the lining of the fish’s gut or, less often, into its flesh.

Mackerel serve the larvae’s purpose only because sooner or later a mammal will eat the mackerel, preferably a dolphin, porpoise, or whale. Once in the stomach of a mammal, the larvae molt and become adult worms. The worms use a mouth like a boring tool to drill into the mammal’s stomach wall. They mate and lay eggs, which emerge in the mammal’s feces, starting the cycle again.

The larvae can end up in a human stomach just as easily as in a dolphin stomach. When a human eats an infested fish without cooking it, he feels a tingling in the throat, and within a few hours may suffer violent abdominal pain and nausea. If he’s lucky, he’ll vomit up the larvae.

If not, he’ll suffer for a week or so until the worm, realizing that it’s not inside a dolphin, gives up and dies. By then, the person’s doctor may have misdiagnosed the situation as stomach cancer. Even without swallowing a live larva, people sometimes react simply to the chemicals in the fish that the larvae produced.

But heat kills the larvae easily. Some people would argue that grilled mackerel smells and tastes so delicious that there’s no point in risking anisakis illness by eating it uncooked.

Nevertheless, sushi chefs continue to prepare and serve mackerel uncooked. In theory, salting the fish and then soaking it in vinegar may well kill the larvae, for the same reasons that salty and
acidic environments kill bacteria. Salt sucks the water from cells, causing them to shrivel. Acids bombard cells with hydrogen ions, warping their enzymes.

Unfortunately, experiments have shown that parasitic larvae can survive for nearly a month in a 20 percent salt solution. Japan has one of the highest incidences of anisakis illness in the world—about 2,000 cases a year.

“
Saba
is also very oily,” Zoran added. “About sixteen to twenty percent fat. The marination helps cut down on the oil.
Saba
also has a very fishy taste.”

Fish that are alive, and fish that are freshly killed, don’t taste or smell fishy at all. A perfectly fresh saltwater fish emits two primary smells. One of these smells is the scent of the ocean—or rather, of the bromophenols produced by algae that fish eat. Surprisingly, the other smell is the odor of geranium leaves. The fats in fish are the unsaturated kind, as they are in plants. Fish skin and plant leaves both contain an enzyme that breaks unsaturated fats down into fragments that smell “greenish” and a bit metallic, like a newly crushed geranium leaf.

Soon after death, however, fish start to smell fishy. Fishiness comes from the same phenomenon that gives fish much of their flavor. In their fight against the osmotic pressure of saltwater, sea creatures fill their cells with tasty amino acids. But fish in particular also fill their cells with a related amine called trimethylamine oxide, or TMAO.

Unlike the amino acids, TMAO has no taste. Nor does it have any smell. But after the fish dies, bacteria on the fish, and enzymes in the fish itself, steal the oxygen away from TMAO, leaving behind TMA.

TMA by itself stinks. It’s what gives old fish their foul smell. It’s also present in human bad breath and in bacterial infections of the human vagina. A rare genetic disorder called trimethylaminuria can prevent people from metabolizing routine amounts of TMA in their food. The devastating result is that their sweat smells like rotting fish. For obvious reasons, it’s a disorder that can cause severe depression.

In addition, bacteria on the surface of the fish quickly digest proteins in the fish after death, creating noxious fumes, including ammonia, putrescine, and cadaverine.

Salting and marinating fish with vinegar doesn’t just help control parasites. It also reduces fishiness.

Covering fish with a heavy layer of salt draws moisture out of the flesh by osmotic pressure. As the water inside the flesh rushes to the surface to dilute the salt, compounds like TMA and stale-smelling fatty acids emerge along with it.

Meanwhile, the acetic acid in vinegar fires hydrogen ions at TMA, just as it does at bacteria. When a hydrogen ion hits a molecule of TMA, the fishy-smelling compound gains a positive electrical charge, which allows it to dissolve easily in water, removing it from the air and terminating the smell.

Mackerel were not the only fish that early sushi chefs salted and marinated. In fact, the sushi vendors on the streets of nineteenth-century Tokyo rarely served anything raw. They had no access to refrigeration. They salted and marinated—or blanched, or seared—all their seafood so it would keep long enough to serve. Sushi chefs in old Tokyo used so much salt and vinegar that people called sushi shops
tsuke-ba
—“pickling places.”

The need for preservation generally had a fortuitous effect; salting and marination often improve the taste and texture of raw fish. One of the reasons for this is that muscle, like mold, contains a lot of enzymes. In muscle, enzymes convert fuel—sugar—into energy. Fish muscle, however, generally contains many more enzymes than the flesh of land animals.

This is partly because fish of many species lead lives of extraordinary self-sacrifice. They consume as much food as they can, building up their muscles and fat reserves, and then they embark on long, grueling migrations. Toward the end of these migrations they manufacture huge masses of sperm or eggs. When they run out of fat during these mating marathons, they literally start to eat themselves for the sake of the next generation. The many enzymes in their flesh deconstruct their own muscle proteins into amino acids. The fish can then use them for energy and the raw material for building sperm or eggs. The closer the fish get to spawning, the more wasted and frail they become.

Like the enzymes in mold, the enzymes in fish muscle continue functioning even after the fish dies. As a result, cooking can actually ruin the taste and texture of fish. If you heat a piece of fish at too low a temperature for too long, the warmth speeds up the work of these cannibalistic enzymes, and the fish eats itself right there in the pan. As with crustacean meat, the result is mush.

Salting raw fish at room temperature, however, lets the enzymes work slowly, deconstructing a little of the protein into the tasty components of
umami.
The salt fends off bacteria long enough for the enzymes to accomplish their task, and the salt itself amplifies the effect of
umami
on the human tongue.

Mackerel flesh digests itself to the peak of
umami
in about twenty-four hours after salting. Any longer and the
umami
degrades. Before the advent of modern transportation, runners from the coast of the Japan Sea carried 100-pound boxes of freshly salted mackerel to the inland city of Kyoto on foot. They hiked all night along thirty miles of mountain paths so that the fish would arrive just in time to reach their peak level of
umami.

Vinegar, meanwhile, unfolds complex fish proteins, firming up fish flesh and turning it opaque. Early sushi chefs also marinated some of their fish in soy sauce to help it keep longer.

To this day, hard-core sushi aficionados argue that to truly qualify as sushi, the fish must
never
be completely raw. Instead, the chef should always somehow alter the fish, whether through salting, marination, or cooking, or some clever combination of preparation techniques.

Zoran ripped the top off the box of mackerel. Kate peered inside. These mackerel were bigger than the previous ones—about 18 inches long. Zoran laid one on his cutting board. He removed the head and guts and cleaned the fish. Now was time to teach the students to fillet.

“Gather round,” Zoran said. He showed them how to cut from the anus back to the tail fin. “Just break the skin first. Once you break the skin you can go in for another try.” He sliced deeper now, his knife blade horizontal, separating the tail muscle from the
ribs. As the knife glided through the animal, Kate heard a series of faint staccato thuds, like a pencil rubbing across a washboard.

“Hear that?” Zoran said. “Brrrrrr.” It was the blade hitting the ribs along the spine. “That’s good,” Zoran said. It meant he was getting all the flesh off the bone.

He spun the fish around and cut from the head along its back in the same fashion, separating the flesh along the backbone. The knife came out at the tail. Zoran lifted off the whole side of the fish. All that was left on the frame was bone.

When it comes to muscle, fish are much more efficient bodybuilders than land animals. Fish don’t waste energy or materials fighting gravity. Butchering a cow by removing its head, hide, feet, organs, and bones leaves only about a quarter of its body weight as muscle. On average, filleting a fish harvests 40 percent of its body weight as muscle—and often more, depending on the season and species. In addition, fish are generally cold-blooded, so they don’t expend energy keeping themselves warm. They are more efficient at converting their food into meat.

Zoran turned the fish over and repeated the process on the other side. Now he had two perfect fillets, plus the carcass.

“
San-mai oroshi,
” Zoran said. The term meant “three-piece breakdown,” the most common fillet technique. Zoran chucked the carcass in the trash and straightened up. “Your turn.”

The students pulled fish from the box and filed back to their stations.

“Once you cut,” Zoran yelled, “it’s very hard to put back together. Think before you cut. We’re in no hurry, guys.”

Kate grasped her knife at the very back of the handle again, to put as much distance between her hand and the blade as possible. She turned away and sawed without looking. The head came clean off. This time, after she gutted the fish she washed it. She even scraped out the bloodline.

Kate stared at her fish. The whole room reeked of the pungent, oily odor of mackerel. Zoran looked at Kate.

“You okay, darling?” Zoran said.

Kate stuck her knife in the fish’s asshole and started cutting.

While everyone’s mackerel fillets lay salting in the refrigerator on woven bamboo colanders, Zoran pulled from the fridge what looked like elongated beige footballs, each one encased in shrink-wrap.

“Albacore,” Zoran said. He laughed. “To the Japanese, albacore is the lowest of the tuna—the worst!” He shook his head. “But Americans like the flavor.” Albacore is most often canned as “white meat tuna.”

Zoran explained that most albacore are filleted and frozen at sea. “We buy them pre-filleted, and when you work in a sushi restaurant, you will, too. You can eat it raw, but because the flesh is so soft, we usually sear it.”

Raw albacore tends to disintegrate under the knife. Searing tightens up the edges. It’s a bland fish, so searing also adds taste.

Zoran extracted one of the long football-shaped pieces of meat from its plastic package.

“The first thing we need to do is feel for bones. If you find them, remove them before cooking.” Marcos nodded. “Now,” Zoran went on, “cut off the belly edge so you can tell your customers, ‘This is albacore belly.’” He smiled. “It makes them feel special, like tuna belly. Honestly, it tastes a
little
different, not much. But it will make them feel like a million dollars.”