What Are Bonito Flakes? Katsuobushi Explained by A Professional Japanese Chef

What Are Bonito Flakes (Katsuobushi)?

Katsuobushi is made from a type of fish called bonito (katsuo in Japanese), a close relative of the skipjack tuna. The flesh is simmered, smoked over firewood, and dried to a crisp (arabushi) or by attaching a fungus to it (honkarebushi) to allow it to ferment.

In Japan, dried bonito flakes are shaved and boiled to extract the aroma and flavor, just like brewing tea, and used as “katsuo dashi” (bonito stock) in all kinds of cooking. This “bonito dashi” is unique to Japan and is an essential part of Japanese cuisine.

Brief history

Japan’s love for bonito, or “katsuo,” goes back to the Yayoi period (300 B.C. – 250 A.D.), when rice farming spread and bonito soup became a popular source of protein.

It was during the Edo period (1603-1867) that katsuobushi, or dried bonito flakes, were made using today’s methods. This period also saw the start of using katsuo dashi (bonito broth), which revolutionized and expanded Japanese cuisine. So, after much trial and error, dried bonito flakes have become a crucial part of Japan’s culinary tradition.

How are bonito flakes made?

Dried bonito flakes are made from bonito fish that are low in fat and not very large in size. This is because high-fat bonito would oxidize quickly, losing quality and making the broth cloudy.

Larger bonitos are more difficult to dry, so only selected bonito are used. Want to know how dried bonito flakes are made? Let’s take a quick look at the process!

Different types

There are two types of dried bonito flakes: “Ara-bushi (荒節)” and “Honkare-bushi (本枯れ節)”. Ara-bushi is katsuobushi that have been smoked without mold and has the following characteristics:

• Has a smoky aroma and strong flavor.
• Tends to produce acidity and astringency in the broth.
• Often used for boiled dishes, miso soup, etc.

On the other hand, “Honkare-bushi” is katsuobushi with the tar removed when “Ara-bushi” is smoked and it’s fermented with an edible mold. Its characteristics are as follows:

• Has richer umami than “Ara-bushi”.
• The mold reduces acidity and astringency, giving it a clean flavor and aroma.
• Has a mild umami taste with less acidity, so it is often used for clear soups.

There are also differences between the different types of katsuobushi depending on the method of shaving. Here are the four types of dried bonito flakes and their characteristics.

• Hana-kezuri (花削り) – “Hana” is the Japanese word for “flower” and hana-kezuri is a type of dried bonito flake shaved super thin, about 0.05 mm, to look like flower petals. It’s the most common type you’ll find. Often used in dishes like soups and chawanmushi, it’s perfect for quick broths where the aroma really matters.
• Atsu-kezuri (厚削り) – Atsu-kezuri flakes are thicker, ranging from 0.3 mm to about 1 mm. Like all dried bonito flakes, less fat is better. Thicker flakes are easier to see, and the shinier they are, the less fat they have. To make broth, simmer these thick shavings on low heat for about 30 minutes. This creates a rich, umami-packed broth, focusing less on aroma. It’s perfect for simmered dishes, miso soup, udon/soba-tsuyu.
• Saihen (砕片) – It is thin, shaved dried bonito flakes crushed into small pieces. Since it is in a fine texture that is easy to eat as it is, it is eaten as a topping for hiyayakko (cold tofu), okonomiyaki, etc., rather than used for dashi (soup stock).
• Funmatsu/powdered (粉末) – Powdered dried bonito flakes can be added directly to dishes for an extra boost of flavor. It’s very convenient and easy to use in wafu pasta, yaki udon, ohitashi (boiled vegetables), and more. Keep in mind the powder doesn’t dissolve completely. If texture bothers you, you can strain it through paper towels. However, since 85-90% of the protein stays in the broth, I recommend using it without straining to enjoy all the nutrients without waste.

How many times can the same dried bonito flakes be used?

Professional cooks like us typically use dried bonito flakes twice when making dashi: Ichiiban-dashi (first time) and Niban-dashi (second time). In writing this article, I dared to try to see if I could get dashi the third time, but it has no aroma and little umami, so I think it should be used up to twice.

To reuse the used katsuobushi after making broth, you can microwave or pan-dry it, add seasonings, and turn it into furikake (sprinkles). However, busy professional kitchens often don’t reuse the already-used katsuobushi and throw it away.

As the concept of sustainable practices becomes more widespread, though I feel like we should strive to make the most of our limited resources.

Umami Factors

Taste, the sensation our tongues perceive, includes umami, a term discovered by the Japanese and now recognized worldwide. Dried bonito flakes contain inosinic acid, one of the three most common umami flavors (glutamic acid, inosinic acid, and guanylic acid).

It is safe to say that dried bonito broth forms the foundation of Japanese cuisine. It’s so essential that cooking without it is like cooking without a knife and cutting board.

Up until about the mid-showa period (1926-1989), even home cooks began their day shaving katsuobushi, but today, many use powdered bonito broth. Japanese restaurant kitchens still start our day preparing dashi broth from dried bonito, using it in soups, miso soup, simmered dishes, boiled vegetables, pickled vegetables, dashimaki tamago, chawanmushi (steamed egg custard), and more.

As the flavor base for every dish, Japanese food and dried bonito flakes go hand in hand.

How to Choose

What should you consider when choosing dried bonito flakes? Each type has unique characteristics, so the best one depends on your needs. Let me explain the four main types, starting with the pricier options.

The four types of dried bonito shavings come from the same fish but go through different processes, giving each its unique traits. Choose the one that best matches your purpose, taste, and budget.

Remember, fish shavings oxidize when exposed to air, so use them quickly. If you have leftovers, store them in the freezer or refrigerator.

Visual Walkthrough & Tips

Here are my step-by-step instructions for how to make Katsuo Dashi at home. For ingredient quantities and simplified instructions, scroll down for the Printable Recipe Card below.

Water is crucial in making dashi, and Japanese water is typically soft. Some countries have hard water, which depends on the region’s soil and landscape. The umami of dashi, like dried bonito, shines best with soft water.

Remember that other aspects of Japanese food and drink culture, such as green tea, also rely on soft water. So, when making dashi, use soft water if possible to get the best results.

How to make awase (combined) dashi

Here’s how to make the basic ichiban dashi soup stock, which combines dried bonito flakes and kelp umami (glutamic acid):

Ingredients

• 1 liter of water
• 30g dried bonito shavings without blood
• 30g kombu (Rishiri kombu, etc.)

3 Katsuobushi Alternatives

If you don’t have dried bonito flakes at home to make dashi, don’t worry! Here are three alternatives you can find at supermarkets or online:

1. Granulated dried bonito flakes like this are popular and easy to use. Just add the desired amount to your dish for bonito flavor. Remember, these granules contain salt, so adjust your seasoning accordingly.
2. Dashi packets like these are like tea bags filled with dried bonito powder (and other elements). Just place a packet in water, heat it, and simmer to make dashi.
3. Shiro (white) dashi like this is a concentrated type of dashi/light soy sauce, mirin…etc. Dilute it with water based on its intended use.

Also, dried bonito isn’t the only type of fish used for dashi in Japanese restaurants. Some other examples include:

• Saba-bushi (mackerel) for simmered dishes, udon, and soba noodle soup stocks, often combined with bonito flakes.
• Maguro (tuna)-bushi produces a light and elegant soup stock, it is often used as a soup stock for clear soup.
• Iwashi-bushi (sardine) are used in miso soup and for soba and udon soup.

Bonito flakes are generally used as the base, but depending on the broth used and the application, the restaurant owner uses a specific blend. The skillful use of different types of dashi broth results in a unique and delicious flavor of each restaurant.

How to Store

Restaurants make dashi fresh every day, but at home, you can save leftovers for later. Homemade katsuodashi can be refrigerated for 1-2 days.

Alternatively, you can freeze it for up to 1 week. You can divide it into conveniently sized portions or even an ice cube tray.