What I learned in Tsukiji: Eat Fresh or Age?

I get asked often, "Are the fishes in Tsukiji caught today?"

But I realized that the professionals working in Tsukiji hates this question, because it's a little silly.

Many, even local Japanese think freshly caught fish taste better, but at least for sashimi or sushi it's better to let it sit or "age" for a few days.

In this post I want to explain why fishes need to age in order to taste better.

Fishes need to age for better taste.

Ask any high end sushi chef which taste better:

1. Freshly caught fish
2. Fish that has gone through shinkeijime and left for several days

There might be a few exceptions, but all chefs will say 2.

Shinkeijime starts the umami enhancement process

Shinkeijime 神経締め is a way to kill the fish with the least amount of stress (at the same time cutting off the nerves and draining the blood)

The shinkeijime process is imortant as leaving the nerves results in rot. That's why the fish shipped to Tokyo go through this process on the fishing boats or in the ports.

When you catch the fish the movement of the fish result in stress, which leads to decrease of ATP.

The ATP is what gradually changes to umami or better taste.

You can keep the condition of the fish about a week or so, which is an ideal aging time for the fish to taste better to full potential.

Japanese TV frequently broadcasts ports selling freshly caught fish, and eating it straight away. This is probably why many Japanese misunderstand that freshly caught must taste best, but actually you won't taste much umami and the texture is firm like rubber when it's freshly caught.

But easier to make money for the ports if it sells straight away.

So in other words and this might surprise you, but Tsukiji won't have the freshest seafood compared to the countryside ports of Japan. Why? It's obvious when you say it, because the freshest is always when it's fished.

So if you are looking for a particular seafood that is "fresh," then your best bet is actually at the port where it's fished. But if you want good tasting seafood, Tsukiji is a very good place to be.

What is Ike 活け？

Another way to keep the potential of the fish is to ship it alive.

I still haven't had the chance to actually see it, but the Toyosu main market logistics people told me the transportation cargos work like fishing tanks, and fishes are transported inside it.

The tanks have good quality water to reduce stress.

These fishes will cost much higher, but can be bought in advance to prepare it to the best condition in the day you will eat it.

The fish shop I work for also have crabs and scallops for example in Ike, still alive.

Fishes are more complex, it's not very cost efficient to have fishing tanks in the shop.

Tsukiji and Toyosu area have many intermediaries keeping the fish in the water tanks.

I have the chance to see the king crabs come in our shop with air infuser in a styrofoam box.

It'll weaken while shipped in the box, but within a few hours in our water tank it recovers its health.

The importance is the air and the water quality in the water tank. 

So is freshness important?

Well of course yes. But more accurately, keeping it in good condition and not having it in the process to rot is.

With that said, it will taste better after being aged. 

So, if you want to have good sashimi or sushi, you shouldn't be looking for fish caught that day. 

Because everyday, the genuine shops that are passionate in what they do, will only sell you fishes that are aged and have them rich in umami to their full potential.

Is aging better for all seafood?

Technically speaking, all fishes will taste better after aging.

White fish like seabream and halibut have the most potential of umami enhancement followed by red fish like tuna and yellowtail. Blue fish rot faster than the others, which makes it more difficult to age well, so it's the most eaten fishes without aging.

Squid, octopus taste much better aged.

Conversely, shellfish, sea urchin, and crabs tend to taste better without aging.

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