Because katsuobushi is a staple of Japanese cooking, it’s fairly easy to find in Asian grocery stores, though the best selection is generally going to be found in Japanese grocery stores. You’ll find katsuobushi packed in resealable plastic bags in one of several shaving sizes (see “Types and Varieties” below for more on this).

Solid blocks of katsuobushi are definitely a specialty item today, and are rarely used anymore even within Japan. If you wish to obtain katsuobushi in this form, you’ll probably have to look for an online retailer. In addition to the block itself, you’ll need to buy a specialized shaver called a katsuobushi kezuriki.

Because most katsuobushi is sold pre-shaved, the easiest way to choose it is based on what you plan to cook and how much you think you’ll need. Look for smaller packages unless you plan on doing a lot of Japanese cooking. To decide what size of katsuobushi is right for a given dish, consult “Types and Varieties” below.

If you plan to purchase whole katsuobushi blocks, make sure to purchase a high-grade, fully fermented piece.

Katsuobushi is quite simple to use, especially when pre-shaved.  When used as a component of a sauce or stock, it is simply added to the hot liquid and allowed to soak for a period of time before being strained out.

Katsuobushi is also used as a garnish or condiment on top of cooked dishes.  In this case, paper-thin shavings are added on top of hot foods, both for flavour and for visual appeal (the heat of the dish causes the shavings to wave and move, creating a rather unforgettable spectacle).

Preparation

The only time katsuobushi requires any special preparation is when it is used directly from a solid block. As mentioned above, this is not common today, even in Japan.

Beyond this, simply give the katsuobushi a sniff to make sure that it hasn’t gone rancid or off. It should smell smoky and naturally fishy, but not rancid or mildewy.

Storage

Once opened, pre-shaved katsuobushi absorbs water easily and can spoil quite quickly as a result. Buy packages based on how often you intend to use the product (note that it’s quite easy to go through if you make dashi even semi-regularly). There are small ‘fresh packs’ available that feature individually packaged portions in a large container. In order to keep your katsuobushi fresh longer, expel extra air from the bag, reseal, and store in a cool, dry, dark location. If the flakes did not come in a resealable bag, transfer them to one immediately.

In order to categorize katsuobushi, we need to look at three factors: species, production, and preparation.

SPECIES

As mentioned in the basic info above, katsuobushi should be made with skipjack tuna (Katsuwonus pelamis).  Occasionally, cheaper true bonito (Sarda spp.) is used instead, though this is more often the case for canned tuna products.  Some countries will not allow the sale of true bonito under the name tuna, but confusion over English names has caused katsuobushi to be labeled ‘bonito’ more often than not.  Because of this, the best indicator that you’re using the right fish is generally price.  All but the cheapest of katsuobushi should be made with skipjack tuna… but it will still be labeled ‘bonito.’  Look for the Japanese word katsuo (鰹).

PRODUCTION

All katsuobushi has been cooked and smoked, but not all of it is fermented.  The following types are differentiated based upon their preparation:

Arabushi – skipjack fillets that have been simmered and smoked, but not fermented.  These are the most common type of katsuobushi in use today, and the variety commonly used to produce pre-shaved products.  If arabushi is trimmed of any odd bits or protrusions, it is called hadakabushi.

Honkarebushi – trimmed skipjack fillets (hadakabushi) that have been simmered and smoked, and then covered in Aspergillus mold and allowed to ferment.  This is ‘true’ katsuobushi, but it is much less commonly encountered today.  The fermentation process draws more moisture out of the fish, making it even more shelf-stable.  It also breaks down the strongly-flavoured fats, yielding a more mellow and less ‘fishy’ end product.  This type of katsuobushi is also called shiagebushi.

PREPARATION

Whole katsuobushi blocks are rarely used today, but if they are they tend to be honkarebushi (that is, true fermented katsuobushi).  Preshaved katsuobushi tends to come in one of three varieties, listed below.  The Japanese names are given to help you shop (though the shapes should be enough to figure out what you’re looking at).

Kezuribushi (削り節) – These paper-thin shavings are the most commonly used variety, and are readily available in Japanese stores.  The name means ‘shaved skipjack.’  The generic term ‘katsuobushi’ (which basically means ‘skipjack pieces’) is often applied to this variety.  One other name, hanakatsuo, mean ‘flower skipjack,’ a reference to the thin, petal-like pieces.  This variety is used for making stocks and sauces and as a garnish.

Ito-Kezuri (糸削り) – Ito means ‘thread,’ a reference to the fact that these pieces have been shaved thinly and then cut into tiny ribbons.  This style of preparation is commonly used as a garnish.

Atsu-kezuri (厚削り) – Atsu means ‘thick,’ a reference to the large chips or chunks that make up this variety.  These pieces impart a strong, smoky flavour to sauces, and are particularly popular for making banno-joyu, a seasoned soy concentrate.

Powdered katsuo – As the name suggests, this is katsuobushi that’s been reduced to a fine powder.  This variety tends to be used as a condiment, but could be used to make stock in a pinch.  Note that there are other inexpensive fish powders used for Japanese food (including true bonito and mackerel), so if you do buy this, make sure it’s actually katsuo.

If you want to make dashi but don’t want to buy katsuobushi, there’s a decent chance that you can get pre-made dashi stock. These instant stocks usually come in boxes filled with packages that look like large tea bags (see image). Instant dashi varies greatly in quality and flavour, but better ones generally contain one or more type of fish. They may not contain skipjack, but may contain bonito or mackerel. Check the ingredient list to help you pick a good instant dashi. The cheapest (and most common) varieties use MSG as the primary ingredient and to impart an umami flavour. While they do a good job of making a rich stock, they lack the depth and characteristic ‘briny’ character that a properly made dashi will have.

If you want to make vegetarian dashi, omit katsuobushi and use just kombu or kombu and dried shiitake mushrooms. Some regional dashi varieties will use small dried sardines in addition to or in place of katsuobushi. If you feel experimental, try using other varieties of dried fish to make stock – the flavour will differ but may work out nicely.

Katsuobushi is not easily replaced as a condiment, but Japanese dried fish powders made from mackerel or other fish may make a suitable substitute.