Narrator: Soy sauce is one of the most
important ingredients in Japanese cuisine.
Yet only 1% of the country's supply
is made through the traditional method of barrel aging.
That's because it can take four years
for one batch to go from barrel to bottle.
Yasuo Yamamoto is a fifth-generation soy sauce maker
and one of the only brewers in the country
who hand-builds his own barrels.
Yasuo: When you make it in wooden barrels, it's delicious.
Narrator: Most fermented seasonings in Japan
used to be made this way, but industrialization
replaced almost all the country's wooden barrels with steel.
Today, the average soy sauce
is made through a shorter, chemicalized process.
So what does it take to make authentic soy sauce?
And how is this centuries-old method still standing?
What makes the soy sauce special
is the wooden barrel, called kioke.
One can last for over a century.
Yasuo makes bamboo strips to wrap around the barrel
because the saltiness of the soy sauce can corrode metal.
Yasuo: But bamboo is resistant to salt
and lasts for 100 years.
Narrator: It takes at least three people
to assemble one barrel,
but not many do this anymore.
After modern machinery took over the market,
almost all kioke makers in Japan went out of business.
So Yasuo learned to make his own.
Yasuo: Now we just need to make it pretty.
Like doing its makeup.
Narrator: Before these barrels are put to use,
crushed wheat and steamed soybeans are mixed with koji,
the fungus that will kick-start the fermentation process.
This giant vat regulates temperature
so the fungus can grow.
After two days, the mixture goes to the moromi house.
This is where the wooden barrels
help create the breeding ground for the bacteria.
Yasuo: The microbes that ferment the soy sauce,
this becomes a home for them.
Narrator: Over one ton of the soybean mixture
fills each barrel, along with salt water.
While Yasuo and his team stir,
the soybeans bump up against each other
and create tiny tears
so that other bacteria can get in
and start to break them down.
The workers pump air into the barrel
to make the aerobic yeast more active.
Even though Yasuo says the microbes do most of the work,
his part of the job is still demanding.
Yasuo: It's hard.
It's punishing, physically.
At the most difficult time,
I lost 9 kilograms in two months.
I think the work is fun even if it's hard.
Narrator: He checks on the soybeans every day
to see if they need mixing,
and based on their scent and appearance,
he can tell where they are in the process.
Yasuo: In my experience, it starts with an apple scent,
and then it makes a banana scent.
Narrator: The soybeans will ferment here
for at least a year and a half.
Yasuo has 87 barrels in different phases.
He believes a good barrel is one that will outlive him.
Yasuo: This wooden barrel has been in use for about 150 years.
Narrator: These types of barrels
have been in production in Japan
since at least the 17th century.
But everything changed during World War II,
when materials became more scarce and expensive in Japan.
The government knew its people couldn't live
without their staple seasoning,
so they ordered factories
to make production cheaper and faster,
cutting the process from years to months.
So while many brewers expanded and modernized,
small businesses like Yasuo's family's
could barely keep up.
Yasuo: So we didn't change to metal tanks.
We didn't have the money to modernize.
Narrator: Yasuo stepped in in 2003,
just before his father suddenly became sick and had to retire.
So he had to take over and pull a struggling business out of debt.
He also had to teach himself a lot of the process,
like how to use the press.
After a year and a half of fermentation,
Yasuo pipes the soybean mixture into this machine.
He layers on a piece of traditional wrapping cloth.
Then the machine slowly squeezes out the soy sauce
over 10 days.
Yasuo: At first, the soy sauce drips off naturally under its own weight,
and you add some more every day.
The weight on top increases, so it slowly starts to press out.
Narrator: Some industrial factories press it all at once,
but Yasuo says getting a quality product
is all about patience.
After this stage, some of the soy sauce
goes back into the barrel with more soybeans and wheat
for two more years
to make Yasuo's main product, saishikomi —
a darker, stronger-tasting soy sauce.
When the microbes have enough time
to naturally ferment the soybeans,
it gives the soy sauce a sweeter aftertaste.
Some industrial brands mimic this by adding sweeteners.
Yasuo: But our soy sauce,
without adding anything,
has a slightly salty taste at first,
but afterward the saltiness disappears and leaves sweetness.
Narrator: That balanced umami flavor
is what chefs like Hitoshi Kishimoto are after.
He's been running his restaurant, Koyomi,
in Shodoshima for five years.
For almost every dish,
he cooks with naturally fermented soy sauce,
including Yasuo's brand.
Hitoshi: The passion they showed,
I think it's reflected in the taste.
For this one, I use five kinds of soy sauce,
and that will bring out the balance.
When you bring them together into one,
it makes a really interesting flavor profile.
I treasure that.
For Japanese people, soy sauce is always nearby.
It's familiar and has a nostalgic taste.
It would be a problem if it didn't exist.
Narrator: In order for traditional soy sauce
to continue, barrel production needs to keep up.
That's why Yasuo holds barrel-making workshops every year.
Yasuo: So we'll train craftsmen
and let people from around the world taste the real thing.
Narrator: He sells his authentic soy sauce
to people all over the world.
A bottle goes for $35 on Amazon,
around triple the price of a commercial alternative.
Yasuo: But if no soy sauce were made in wooden barrels,
wouldn't the real thing be lost?
Narrator: For Yasuo, passing down the legacy
of barrel-aged soy sauce is part of his life's mission.
Yasuo: I think of it as a relay race.
It is my job to pass on this brewery,
the barrels, and the microbial ecosystem.
When my grandchildren and great-grandchildren visit my grave,
they'll say, "Grandpa made barrels, so now we make barrels and soy sauce."
That would make me happy.
That's why I do it.
I think there should be variety and choices.
There wouldn't be enough if it was all made in wooden buckets.
If they take apart the buckets we built
I hope they notice the innovations I made.
That's where the romance lies.