I Went to Numazu and Found an Old Food Technology

Today, no AI.
No code.

Just fish.

A few days ago, I took a short trip to Numazu, a coastal city in Shizuoka, Japan.

Numazu is one of those places where fish feels very close to everyday life.

You walk around, see the harbor, seafood restaurants, fish shops — and eventually, you get hungry.

So I did what seemed like the obvious thing.

I ate fish.

More specifically:

Aji no himono — dried horse mackerel.

It looked very simple.

A grilled fish, opened flat, with rice and grated daikon radish.

But while eating it, I started thinking:

This is actually technology.

What is himono?

“Himono” literally means dried food, but in everyday Japanese it often refers to dried fish.

For aji no himono, the fish is usually opened, salted, dried, and then grilled before eating.

That's basically it.

No complicated sauce.

No long list of ingredients.

Fish.
Salt.
Air.
Time.

But that simplicity hides a surprisingly clever process.

The original problem: fish doesn't keep well

Fresh fish contains a lot of water.

That's one of the reasons it tastes good.

It's also one of the reasons it spoils quickly.

Today, we have refrigerators and freezers.

People in the past didn't.

So they needed another solution.

One answer was simple:

Remove some of the water.

Drying lowers the amount of water available for microorganisms and slows deterioration.

In modern food science, this is related to the concept of water activity.

So himono is not just “fish left outside.”

It is a method of controlling water.

And that changes everything.

It's really a tuning problem

The interesting part is that you don't want to remove all the water.

Dry too little, and preservation doesn't improve enough.

Dry too much, and the fish becomes hard and unpleasant.

So you're balancing several things at once:

• preservation
• moisture
• texture
• saltiness
• flavor

That sounds familiar.

It's a trade-off.

You could almost describe himono as an old optimization problem.

Preserve the fish, but keep it delicious.

People solved that problem hundreds of years before anyone called it engineering.

Salt isn't just seasoning

Salt also plays more than one role.

Of course it makes the fish taste good.

But it also helps draw water from the fish and changes the environment in which microorganisms can grow.

So salt is not just a topping.

It's part of the process.

The recipe is closer to this:

Fish + salt + controlled drying + time

And after that process, the fish is no longer quite the same food.

The texture changes.

The aroma changes.

And the flavor changes.

Then there is umami

This is where Japanese food gets especially interesting.

The Japanese word umami is now widely used around the world.

It is generally described as the fifth basic taste, alongside sweet, sour, salty, and bitter.

Fish naturally contains compounds connected to umami, including glutamate and nucleotides such as inosinate.

And an important point is this:

Drying doesn't magically create umami from nothing.

It's more subtle than that.

By reducing water, adding salt, changing texture, and allowing biochemical changes during processing, the experience of the flavor becomes different.

The taste feels deeper.

More concentrated.

More satisfying.

And that's one of the things I noticed while eating the fish in Numazu.

There wasn't much on the plate.

But it didn't feel simple at all.

Maybe that's why I like Japanese food

When people think of Japanese food, they often think of sushi.

Or ramen.

Those are great.

But some of the foods I like most are much less spectacular.

Grilled fish.

Rice.

Miso soup.

Pickles.

A little grated daikon.

Nothing flashy.

And yet, behind something as ordinary as a piece of dried fish is a long history of people experimenting with:

water, salt, time, temperature, texture, and taste.

That's engineering.

Just not the kind we usually write about on DEV.

A small discovery in Numazu

I went to Numazu just expecting a short trip and some good food.

I came back thinking about dehydration, preservation, and umami.

That might be an occupational hazard of being an engineer.

But I like finding technology in ordinary things.

And himono is a good example.

It looks like a simple grilled fish.

But behind it is an old idea:

Control water, and you can control preservation.

Then keep improving the process until preservation and deliciousness can coexist.

Humans have been optimizing systems for a very long time.

Some of them just happen to be edible.

So if you ever visit Japan, try sushi.

Try ramen.

But if you find yourself somewhere like Numazu, look for something simpler.

Aji no himono.

You might be eating a small piece of Japanese food engineering.