On this page, you can learn what Katsuobushi is.


Katsuobushi(かつおぶし) is food and the long dark object which looks like a block of wood in the photo.

There are three key words to describe Katsuobushi:

  • dried
  • fermented
  • smoked


Katsuo(かつお)means Skipjack tuna which can be up to 1 meters in length.

Hard enough to make a knife

Guinness World Records considers Katsuobushi the hardest food in the world. Katsuobushi is so hard that you could make a knife out of it.

Why so hard?

Smoking is the process of preserving food and it gets harder if smoked.

Katsuobushi was born over 1000 years ago when people didn’t have refrigerators or freezers, so they had to think of the way to preserve fish without those appliances.

Katsuobushi got harder and harder as they improved how to smoke Skipjack tuna over the years.

To shave Katsuobushi

Japanese people do not eat Katsuobushi as it is. Because it’s too hard! They shave it to make bonito flakes which are used to make fish broth. The broth is used to make different Japanese dishes including miso soup.