Japanese Hardest Food of Tuna - Traditional Smoked Tuna Production Process - Tuna Processing

Katsuobushi (Japanese: 鰹節) is simmered, smoked and fermented skipjack tuna (sometimes referred to as bonito). It is also known as bonito flakes or broadly as okaka (おかか).

Shaved katsuobushi and dried kelp—kombu—are the main ingredients of dashi, a broth that forms the basis of many soups (such as miso) and sauces (e.g., soba no tsukejiru) in Japanese cuisine.

Katsuobushi's distinct umami taste comes from its high inosinic acid content. Traditionally made katsuobushi, known as karebushi, is deliberately fermented with Aspergillus glaucus fungus in order to reduce moisture.

Today katsuobushi is typically sold in bags of small pink-brown shavings, which vary by thickness: smaller, thinner shavings, called hanakatsuo (花鰹), are used as a flavoring and topping for many Japanese dishes, such as okonomiyaki, while the larger thicker, called kezurikatsuo (削り鰹), are favored for making the widely used dashi stock.