Natto: When tradition makes flavor better

Natto is a fermented food commonly found on dining tables across Japan. In early March, I visited a natto factory in Mito. The production plant uses traditional methods, including shipping its beans in straw bundles.

Ibaraki Prefecture is the nation's top producer of the sticky, fermented soybeans. Natto from Mito is said to have been a popular souvenir in the Meiji era (1868-1912) because its smaller beans were thought to be especially delicious.

"We sometimes go and inspect soybean production sites in Aomori or Miyagi prefectures," said Daisuke Takahoshi, a senior managing director at Mito Natto Seizo, a Mito-based maker of natto founded in 1929. Takahoshi is set to become the company's fourth president. Eighty per cent of the manufacturer's products are made using domestic beans.

Inside the plant, the sweet fragrance of soybeans hung in the air. After being soaked overnight until they expand, the beans are braised in a massive pressure cooker that can process about 90 kilograms of beans in an hour.

"We can't take our eyes off the cooker because if the beans are overcooked, they'll turn black and lose their flavor," Takahoshi explained.

Once cooked, the beans are sprayed with a strain of bacillus subtilis designed for natto and mixed thoroughly. Then about 70 grams are placed atop a bundle of straw.

The mixture is covered with another layer of straw, and the bundle is tied at both ends. By doing so, the straw's fragrance is imparted to the beans, which enhances their flavor.

Because the beans are not sealed up like those shipped in Styrofoam packs, the water also drains away, allowing the final product to achieve the optimum degree of firmness. As a delicate fermented food, natto must be made by hand with the utmost care, according to the company.

The beans are fermented in a specialised room for 18 to 20 hours while the temperature and humidity are fine-tuned according to the weather and variety of bean.

"In premium-grade natto, a layer of bacillus subtilis forms around the beans, making them appear as if they're dusted with a white powder," Takahoshi said. "This kind of natto is more delicious because it offers a robust flavor, good texture and sticky strings." The products are shipped after being matured in a fridge for three to five days.

The more fermented natto beans are, the more flavor-boosting umami they contain. This is why natto is best consumed just before its expiration date. After removing the beans from the straw, I stirred them about 30 to 40 times as instructed. The beans grew stickier.

Unlike the Styrofoam-packed natto that I usually buy, Mito Natto Seizo's natto smells faintly of straw, and each bean was plump with a firm texture.

Akiko Anzai, the chair of a diet and nutrition committee in Mito, has been promoting the use of natto in recipes.

"We're trying to spread the word about easy-to-make recipes so that natto can be a part of everyone's diet," Anzai, who is in her early 70s, said.

Natto menchi, which uses natto as a substitute for minced meat, is one such recipe. The fermented soybeans are mixed with bread crumbs, finely cut onions and other ingredients, then fried. The dish brings out the rich flavor of the natto beans.

Natto no tamago-yaki combines natto and salted kelp in a Japanese-style rolled omelette. Its mild, sweet flavor must be popular with children. A popular side dish among local residents is cooked abura-age (deep-fried bean curd) stuffed with natto and green onion. It is said to go best with alcoholic drinks.

"Natto becomes less sticky when it's heated," Anzai explained. "For people who aren't accustomed to natto, that makes it easier to eat." Anzai - who says she always eats natto every morning - attributes her good complexion and youthful appearance to the habit. I'm tempted to follow her example.

In Ginza, varieties for every taste

Ibaraki Prefecture's Ibaraki Marche antenna shop, located in the Ginza district of Tokyo, offers 35 varieties of natto by Mito Natto Seizo and other local manufacturers.

Among the products are kyogi natto - whose beans are wrapped in kyogi, or paper-thin sheets of wood - and soboro natto, in which the beans are mixed with kiriboshi daikon (thinly sliced and dried daikon Japanese radish).

Another variety is hoshi natto, which is sun-dried natto that can be eaten with your hands. The shop accepts orders by phone at 03-5524-0818.