Mikio Atobe carefully peels a layer of rayon netting from a chunk of farmed bluefin tuna, revealing a secondary sheet of cloth clinging to its exposed flesh, partially yellowed by the mold coating it.

“Take a sniff,” said the 43-year-old chief executive of Meat Epoch Co.

“You see, it doesn’t emanate that distinctly fishy smell. Let this rest in the fridge for up to 20 days and you’ll have quality aged tuna in around half the time it would normally take.”

Atobe heads a startup producing what it calls Japan’s first “aging sheets” — elastic netting lathered with spores to facilitate the dry aging of raw beef, fish and other types of animal flesh to bring out umami — a pleasant savory flavor. Umami is described by some as the “fifth taste” alongside salty, sour, sweet and bitter, that is found in foods like cheese and tomatoes.

The former chef also heads Foodism Co., which runs gyōza (dumpling) restaurants and eateries serving dry-aged meat in Tokyo. He says the spores used in his sheets prevent aged beef and fish from getting discolored, and extends their shelf-life while softening the texture and adding a distinct nutty scent.

While dry aging typically involves storing animal flesh in near-freezing temperatures in a chilled processing facility and leaving it there for weeks, months — or in some cases, years (for the “extreme” aged beef served to uber-connoisseurs) — he says his invention has succeeded in speeding up the process substantially by smothering its surfaces with fabric soaked with zygomycete fungi from the genus Helicostylum.

It’s the brainchild of Atobe and Shuichiro Murakami, a professor at Meiji University’s School of Agriculture. They say the product could revolutionize the meat and seafood industry.

The concept originated out of laziness, Atobe said.

A tanned, astute man who seems more comfortable in chef’s whites than business suits, he was an itamae (chef) at a Japanese restaurant for 10 years before venturing into other fields, including food consulting, before opening his first gyoza shop in 2009.

After a rocky start, the restaurant took off after a few years, and Atobe began looking for new ideas when he happened upon a buzzword: dry-aged beef, a product that has been enjoying an expanding global market led by the United States, where its size is forecast to reach $11.2 billion, according to Allied Market Research.

“I began eating at restaurants serving aged beef, and experienced an epiphany when I sampled the excellent slices I purchased at Nakasei,” he said, referring to a famed specialty shop headquartered in Tokyo’s Setagaya Ward. Hooked on the rich, condensed flavors of the artisan meat, Atobe decided to capitalize on the growing popularity of the delicacy and launched his restaurant, Shunjukusei, in 2012, serving beef and pork aged up to 100 days and 40 days, respectively.

Dry aging is a costly and time-consuming process that has been likened by some to an art.

Soon after an animal is killed, its enzymes begin to break down its muscle fibers, softening its flesh and releasing the amino acid glutamate — the source of umami. Simultaneously, the animal’s fat oxidizes while water evaporates from muscle tissue and mold spores in the air accumulate on the outer layer. Depth in flavor and texture can be attained by carefully regulating this process, but various factors can affect the quality of the end product. The meat then loses a significant portion of its weight through evaporation, and even more before serving time, when its darkened, inedible husk is trimmed.

Atobe perfected his own style of aging through trial and error and would describe the process to curious customers. But he was frustrated he couldn’t explain the exact science behind the phenomenon.

“So I consulted one of the regulars who introduced me to professor Murakami, and we soon began working together,” he said.

“But as we conducted research it became apparent there were toxins and other microorganisms that were inhibiting the quality and safety of aged meat, which made me ask: ‘Isn’t there an easier way to make it?'”

In an interview posted on Meiji University’s English website, Murakami said that among the various fungi growing in Atobe’s climate-controlled aging room, he detected a harmless, superior type and began experimenting with ways to single out and artificially apply it to meat. He initially tried spraying, but had difficulty covering the meat uniformly. He later found a solution by immersing sterilized cloth in a fungus suspension.

“The advantage of aging sheets is that the spores adhered to the cloth grow so much that they completely cover the meat within around 10 days. Consequently, dry aging, which previously took three months, has come to need only around one month,” he said.

The special cloth also markedly reduces the risk of other microorganisms forming on meat and posing a safety risk, he added, noting the process requires only a thin layer of the surface to be trimmed, meaning better weight retention and more meat to serve.

The project, which began in 2014, wrapped up in 2016, and they applied for a patent before marketing it to businesses in 2017. The aging sheets cost ¥4,800 for a spore cloth measuring 1 meter by 50 cm, which is enough to wrap around 20 kg of meat. They aren’t available to the general public yet.

Atobe didn’t just stick to meat, however. Last year he began testing the product on one of Japan’s main staples: fish.

“There would naturally be great potential if this technology can be applied to fish, since we’re a fish-eating culture,” he said.

So he teamed up with the Hokubu Shijo fish market in Kawasaki, which was looking for a new draw to shore up its dwindling seafood sales. While Japan is one of the world’s top seafood markets, consumption has been on the decline since 2001, according to the Agriculture, Forestry and Fisheries Ministry.

After nearly six months of trials, Hokubu Shijo announced in November it would begin selling aged fish made using Meat Epoch’s aging sheets online and to restaurant chains.

“It’s quite a hit with customers, although whether people prefer it to regular sushi depends on personal taste,” said Soichiro Hoshino, a sushi chef at the Kawasaki branch of Uogashi Nihonichi, one of the three sushi chains run by Nippan Co. that serves dry-aged fish bought from Hokubu Shijo.

Compared to a regular serving of akami maguro (red meat tuna) sushi, for example, aged tuna has a distinctly different, sticky texture with little or no fishiness and a mild sweet aftertaste reminiscent of cheese.

Like meat, the process of aging fish has been around for centuries and can be seen in many countries in the form of fermentation, smoking or salt-curing. It also requires a controlled environment with carefully monitored temperature and humidity.

After fish are gutted and cleaned, however, they need to be wrapped in cloth or paper to absorb moisture from the aging process, a step that calls for extensive care. One wrong step could spoil the fish, inevitably raising costs.

“One major issue with this method is the amount of fish meat you lose through evaporation and trimming,” said Kohei Inoue, deputy chief of corporate development at Nippan, a company that runs dozens of sushi and other Japanese restaurants in and around Tokyo.

“We used to dry age tuna ourselves but would be left with only around 40 or 50 percent of the fish,” he said. “But by using fish treated with the aging sheet, we only need to trim the surface directly underneath the cloth, leaving us with around 70 to 80 percent of edible fish meat.”

Inoue also pointed out the benefits of aged fish’s long shelf-life, especially when frozen — an aspect Atobe believes could even impact the logistics of seafood transport.

“Oxidation in food is a natural process, and that’s what leads to rotting. But it also produces amino acids that creates umami.

“On the other end of the spectrum, fermentation produces antioxidants that prevent spoilage, which may be what is happening in aged meat and fish that don’t seem to rot easily — a topic we will research further this year.”

Fermented food products, from seasonings to drinks, have traditionally been at the heart of Japan’s healthy diet, Atobe said, a culinary tradition that inspired him to rename the Ginza branch of his aged-beef restaurant to Shunjukusei Hakko (hakko meaning fermentation), which reopened its doors on Feb. 21.

At a sampling party on Feb. 18, Atobe premiered some of the dishes the restaurant will serve, including dry-aged salmon and beef made with aging sheets, and an array of condiments and cocktails featuring fermented vegetables, fruits and grains.

His experiments are far from over, however. Atobe has found himself traveling across Japan with his aging sheets, wrapping up whatever seafood he comes across.

“We’re getting better at this — recently I went to Hokkaido and rolled up sockeye salmon and herring. The other day I visited a fish market in Yokohama and rolled up a bigeye tuna,” he said.

“But we’re in no way close to trying out all types of fish — there are just so many out there.”

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