A technique developed 34 years ago by chance is now in wide use to preserve a variety of foods, including sashimi, dairy products, vegetables and Tottori Prefecture’s 20th Century-brand pears.

The technique to keep foods fresh at temperatures just above their freezing point is called “hyo-on” in Japanese.

Akiyoshi Yamane, who died six years ago, came up with the technique while experimenting with the freshness of 20th Century pears during his term as director of the Tottori prefectural food processing research institute.

He intended to keep four tons of pears at 3 degrees, but it turned out they were accidentally left at minus 4 for four days.

He thought the pears were spoiled and would have to be dumped. Instead, he found they remained fresh and retained a sweet taste.

However, he was doubtful at the time whether it was correct to call food stored at temperatures just above zero “chilled” and those at temperatures below that level “frozen.”

While carrying out a variety of tests, he discovered that optimum freezing temperatures differed according to food and that the temperature just before freezing was what made it possible to derive the best taste.

He named the temperature of that condition hyo-on.

It was later learned that the amount of harmful microorganisms decreased from perishables that were kept chilled and enabled them to last three to five times longer than those that were frozen.

The taste of such food also had improved, without requiring additives.

The hyo-on process made good use of legacies handed down from older generations, such as taking advantage of winter to dry fish overnight.

In the fishing port of Ajiro in the town of Iwami, Tottori Prefecture, women work inside a hut preparing flatfish to dry overnight.

They also add sweet sake seasoning to other kinds of fish before putting them up to dry. The fish are later sold door-to-door in Tottori and other cities.

Fishermen caught a good haul of “akagarei” flatfish in the Sea of Japan between November and February, cleaning the fish as soon as the catch was unloaded.

They coated the fish in salt before washing them off an hour later and exposing them to the wind.

Akihiko Yamane, 44, president of Hyo-On Laboratories Inc., founded by his father, Akiyoshi, in Yonago, Tottori Prefecture, said: “Drying flatfish overnight is natural hyo-on technology. The (fish) cells in cold weather raise the permeation pressure of cell fluids to keep themselves from freezing.

“In the process, they produce such tasty ingredients as inosinic acid,” he said. “And that’s why the flatfish become tasty.”

Yamane’s late father established the research office after retiring from the food processing research institute and registered the Hyo-On trademark with a government office.

He was involved in certifying hyo-on food, and cooperated with an electrical machinery company in the manufacture of hyo-on storage and chilled storage vehicles.

At present, there are about 370 kinds of hyo-on food, including vegetables, fishery products, “natto” fermented soybeans and noodles.

It became known about 10 years ago that slices of sashimi become even tastier if they are kept at a low temperature.

Morihiko Sakaguchi, a Kyoto University professor emeritus, said studies show that fish for sashimi is almost without any inosinic acid immediately after blood is drawn from it.

However, the substance rose to a maximum when young yellowtail and sea bream were stored at low temperatures for eight to 12 hours, and 17 hours in the case of “hirame” sole.

Tottori Prefecture’s National Federation of Agricultural Cooperative Associations (Zenno) exported 20th Century-brand pears to Taiwan for the first time on an experimental basis in January in time for the Chinese Lunar New Year.

The pears were kept at a chilled temperature for four months after they were harvested. They proved popular both in terms of their sugar content and their appearance, which remained unchanged from the time they were picked.

In the next season, Zenno plans to go all out in shipping pears.


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