The next day, I traveled by bus across the Akashi Kaikyo suspension bridge to Shikoku, in the inland sea, an island so beautiful I regarded it from the window in a kind of blissful trance. There were gentle mountains and gorges packed tight with tombstones; distant glinting seas; giant wheeling tombi hawks silhouetted against a crisp, blue sky; rice-straw wigwams drying in the sun; and ceramic-tiled wooden houses, as seen in dozens of samurai movies.

I was traveling to Shikoku Island to taste the world’s greatest soy sauce, the soy equivalent of cold-pressed, extra-virgin, single-estate olive oil or fifty-year-old Modena balsamic vinegar, a true gourmet rarity produced in the traditional method by the descendant of a samurai family.

But first, the supermarket stuff.

The single most important ingredient in Japanese food is not rice—which is more than a mere ingredient; it is virtually a spiritual element to a meal—but soy sauce. Though the Japanese do use salt in their cooking—and, as I was to discover on Okinawa, they produce some of the greatest salts in the world—the majority of their season- ing comes from this fabulously savory, ebony brown, viscous liquid.

They consume on average over two gallons per capita per year of various types: light and salty usukuchi, traditionally associated with the west of Japan; less salty, dark koikuchi, traditionally favored in the east of Japan and accounting for 80 percent of the market; an- other soy made with equal parts wheat and soybeans; one made with added amazake, a fermented rice drink; as well as saishikomi, shiro, and tamari soy, the latter thicker and richer and made using little if no wheat.

One soy company dominates both the domestic and global soy markets. Kikkoman’s distinctive little squat-bottomed bottles with the double-spouted, brittle, red plastic screw tops are ubiquitous the world over, found on every table of every Chinese and Japanese restaurant from Washington to Wolverhampton, and in most domestic kitchens, too. The company has plants in Holland, China, and the United States, producing over a hundred million gallons per year. It is the Coca-Cola of the soy sauce world. And the Pepsi, as well. Well, can you name another soy brand?

Japanese soy has traditionally been made in Chiba Prefecture, in either Choshi or Noda, and sailed down the river to Tokyo. It has been exported farther afield since the seventeenth century—Louis XIV was said to have been a fan. Kikkoman started in Noda three hundred years ago, and it still has its base there. Back when we were still in Tokyo, at the beginning of our journey, almost two months earlier, I took a train there, twenty miles north across the endless expanse of Tokyo’s suburbs.

Noda is very clearly a one-company town. The air was thick with the meaty smell of soy sauce—a kind of sweet, beefy, wheaty aroma—but Kikkoman didn’t appear to have brought great wealth to Noda, which was a rather bleak, ramshackle, low-rise place, dominated by the giant, rusting hulks of wheat storage tanks.

I had hoped to visit Goyogura, the brewery dedicated solely to making soy sauce for the imperial household, but it was undergoing renovation. Instead, Hiroyuki Yano, a nice man from the PR department, showed me around the visitors' center, starting with the dreaded corporate video ("Defying the passing of time and national boundaries, since times of old, that's Kikkoman!"), before we followed the process of turning soybeans into soy sauce, or shoyu, via windows into the factory itself.

It is a surprisingly straightforward process, which probably explains why home brewing of soy was commonplace in Japan until World War II. The main ingredients are steamed soybeans and roasted, crushed wheat—in Kikkoman's case, non-GMO and grown in the United States and Canada (the emperor's soy sauce is made exclusively with domestic ingredients, of course). These are fermented using the Kikkoman Aspergillus oryzae bacteria, a type of koji, which is mixed with brine to make a mash called moromi and left to develop for six months. Sugar and amino acids combine to create that deep caramel color while yeasts and lactic acid create the aromas—there are three hundred different aromas in soy, apparently, a figure comparable to wine. The moromi, an unpleasant-looking orangey-brown mash, is churned and then pressed in 2,800-yard-long nylon sacks before being pasteurized.

What was the difference between this and how the Chinese make their soy? I asked Yano-san. “The fermentation process is different. Some of the Chinese ones are made by a chemical process.” He sniffed. “They can use acid to take the protein from the beans, for instance.” Some companies also add corn syrup and artificial caramel, or even hydrolyzed vegetable protein and hydrochloric acid, but not Kikkoman.

Until thirty years ago, Kikkoman made its soy sauce by fermenting the moromi in traditional wooden trays, a method originally devised because it allowed the temperature to be easily regulated by lifting the trays to control the circulation of air. These days they use giant, glass-lined, temperature-controlled stainless steel tanks. There are two thousand of them in the Noda plant alone, although this isn't the biggest Kikkoman factory—that is in Wisconsin. This vast scale of production enables the company to sell its soy sauce for less than the cost of bottled water in some territories.

I was impressed by the straightforward, relatively “slow food” brewing process at Kikkoman, but a chance tasting of another, far subtler, richer, and softer artisanal soy in a restaurant in Kyoto sent me off on the trail of a rather more refined soy sauce, made at the Kamebishi brewery, on the island of Shikoku.

Kamebishi is the only soy company in Japan still making soy sauce the old-fashioned way, using the mushiro method, in which the fermenting beans are spread out on woven straw mats placed on top of bamboo trays. The resulting mash is left to mature for a minimum of two years.

Kamebishi was founded over two hundred years ago and is still run by the seventeenth generation of the Okada family, originally of samurai stock. The factory remains in the small rural town of Higashikagawa, in the original samurai house, a sprawling, single-story red stucco farmhouse with a heavy ceramic-tiled roof.

In charge when I visited was Kanae Okada, who returned from a high-flying career in the travel industry in Tokyo to rescue the family firm some years ago. “When I was growing up, I never wanted to be a part of it, and my father didn’t force me,” Kanae told me. “I went off to work in the U.S., worked in Tokyo, and had a child. I worked at the Japan Cultural Center, and many of my colleagues there had a cultural specialty, like kabuki or sumo, and I felt so ashamed that I had neglected this part of my heritage. In the States it was the same. Everyone was so interested in my family, but I couldn’t answer any of their questions. So I returned fifteen years ago to start running the company.”

Kanae recognized the cultural and commercial importance of her family’s product and was determined to save the company from the brink of bankruptcy. This she has done with a mix of shrewd business sense, a respect for traditional methods, and some remarkable new product innovations, including freeze-dried soy for use as a seasoning, and a soy sauce that she has aged for—so far—twenty-seven years.

"We are very different from Kikkoman," Kanae told me as she showed me around. "We roast our wheat on hot sand to 400°F. We use whole soybeans; they use dried beans with the oil removed. We ferment the moromi on straw mats on top of bamboo slats at between 82°F and 86°F. We age it for a minimum of three years in cedar barrels. It is very intensive, very intuitive."

Kanae is the first woman in Japan to run a soy company. What about her sixteen-year-old daughter? I asked. Will she take over the company one day? “Actually, she isn’t like I was when I was growing up. She is really proud of what we do. She comes with me on business trips and explains things to clients. Many young Japanese are fed up with being white-collar; they want to make things. We used to have a real problem getting workers—you know, we are quite a way from anywhere here—but we get many young people coming to work here now. Only a few can cope with the hard work, but I think they will come back to the old ways. Ten years ago we were having a real crisis. Sales were dead, but now they have doubled.” Perhaps the traditional sectors of the tofu and sake industries could benefit from a similarly dynamic, innovative approach.

We clambered up into the dark, cobwebbed loft where the hundred-year-old cedar barrels containing the slowly fermenting soy are kept—all the better to control the flow of air and, thus, the temperature. Every surface—walls, floor, old pipes, ceilings—was caked with a thick, tar-like crust. We gingerly tiptoed across the tops of the barrels—essentially large wooden tanks set into the floor. It reminded me of Fagin’s London, and I must have pulled a bit of a face, as Kanae said, “You know, it isn’t dirty. It is decades of fungal growth, but actually, the whole process is extremely hygienic even though we never clean it. Someone from the government’s hazard analysis department came and said we had to clean everything, but I had to explain that this environment is exactly what makes our soy taste so special. The mold here is more than two hundred years old! We did tests and found 230 different types of bacteria, yeast fungus, and microbes—all of them are part of our fermentation process. These microfungi produce lots of alcohol, so in the summer it gets above 104°F and really smells of booze.” In other words, the entire building was alive with fertile microorganisms, a giant fermentation chamber.

The floor was slippery, and the barrels about seven feet deep. Had anyone ever fallen in? I asked. “Yes, I did once, when I was four. It was full of soy, too. Luckily there was someone to fish me out, or I would probably have died.” For the first two nights of fermentation, someone has to babysit the mash, stirring it and maintaining the right temperature, but the result of this incredible attention to detail is a soy that is richer and smoother tasting than supermarket soy. It sells for roughly twice the price, but that is still, to me, cheap for an artisanal product.

We retired to Kanae’s office to talk about the future of soy. “I started to make soy salt for the French and Italian chefs because they couldn’t season their food with soy sauce because of the color. Now lots of Italian chefs are using it. It is packed with umami. You can think of it as natural MSG. Pascal Barbot and Alain Ducasse are very interested in using it.”

Then she brought out the “special stuff.” “And this,” she said, proudly brandishing a bottle whose contents were pitch-black and syrupy, “is the twenty-seven-year-old aged soy. The only aged soy in the world. I got the idea when I visited a balsamic vinegar producer in Modena who had a hundred-year-old balsamic, which tasted incredible. We are not going to sell this until it is fifty years old, but you can taste it now if you like.” It was rich and deep, with a powerfully lactic taste, hints of sherry, cedarwood, and grilled steak, like a refined, complex Marmite but without the afterburn.

They also sell a ten-year-old soy for around $150 a bottle—presumably the most expensive soy sauce in the world—which, though not quite as intense, is wonderful drizzled over carpaccio, just like balsamic. Even more exciting were Kanae’s plans for the future, which include soy maple syrup for ice cream, chocolate soy flakes, caramel soy, and balsamic soy salt. “The chocolate isn’t quite ready—it needs more of an umami boost.” (Since my visit, the chocolate has been perfected and is now on sale.)

Wandering around after our meeting, while waiting for my bus, I chanced upon another ancient, artisanal food producer, making wasanbonto sugar. This is the "king of sugars"—primarily sold as ultrafine sugar bonbons, little balls the size of peas wrapped in tissue paper and made by hand from sugarcane for over two centuries. Legend has it that a pilgrim from southern Kyushu, at that time the only place allowed to grow sugarcane in Japan, walked all the way to Shikoku smuggling a chikuto sugarcane plant and, upon arrival, collapsed and died. They planted the sugarcane, and as it turned out, the soil and water here were perfect for its cultivation. The cane flourished, and when processed, by squeezing, then boil- ing the juice, and then stone-pressing the syrup to refine it, it produced much smaller, powder-sized crystals than the same plants grown in Kyushu. At ¥3,000 (around $40) per 2.2 pounds, it is today the most expensive sugar in Japan. I just had time, as my bus came into view, to buy some of the company's bonbons, which were extraordinarily fine. They dissolved quickly on my tongue, leaving a faintly flowery, sweet aftertaste.

Excerpted from SUPER SUSHI RAMEN EXPRESS by Michael Booth. Published by Picador. Copyright © 2016 by Michael Booth. All rights reserved.

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