In this article, we’ll delve into the fundamental knowledge of sushi, focusing on the sushi ingredient “akami” or lean meat. When we hear “akami,” many people immediately think of tuna, but akami sushi ingredients aren’t limited to just tuna. Even within tuna, there are various cuts used for akami sushi, and there are other fish that are considered akami despite their appearance resembling white meat. Let’s explore the world of akami and enhance our sushi knowledge.
What Is Akami in Sushi?
In the world of sushi, fish are categorized visually as akami (lean meat), shiromi (white meat), or hikarimono (silver-skinned fish). Akami and shiromi are distinguished by the color of the fish’s flesh, while hikarimono refers to fish with a blue back and a shiny belly. Akami, as the name suggests, refers to fish with red flesh. However, in the sushi world, fish with red flesh doesn’t necessarily mean the entire fish is red. Sometimes, fish can have a blue back and a shiny white belly while still being classified as hikarimono.
Why Do Some Fish Have Red Flesh?
The difference in color between akami (red flesh) and shiromi (white flesh) is due to the types of muscle fibers and proteins found in the fish’s blood. Fish have two types of muscle fibers: slow-twitch (red muscle) and fast-twitch (white muscle). Fish that have to swim actively over long distances, like tuna and bonito, possess red muscle, which is known for endurance. Just like humans, fish require oxygen for movement, and red muscle contains a higher concentration of oxygen-carrying pigments like hemoglobin and myoglobin, which give it a reddish color. This is why the flesh of these fish appears red.
On the other hand, fish with white muscle, like some non-migratory species that don’t constantly swim long distances but rather stay near the seabed and move quickly to catch prey when needed, have less myoglobin and fewer pigment proteins, resulting in a paler appearance.
Classification of Akami and Shiromi
In fisheries science, fish are classified as either akami or shiromi based on the amount of pigment proteins present in their flesh. Fish with more than 10 mg of pigment proteins such as hemoglobin and myoglobin per 100 grams of flesh are categorized as akami, while those with less than 10 mg are considered shiromi. According to this definition, saury (sanma) falls under akami, even though its flesh appears white. Saury is often mistaken for shiromi because of its color. Conversely, yellowtail (hamachi) has pale flesh but is classified as akami due to its higher pigment protein content. Salmon, which is often mistaken for akami despite being shiromi, gets its reddish flesh color from its diet of crustaceans (small shrimp, crabs, plankton) that contain astaxanthin pigment.
Characteristics of Akami
Akami from migratory fish, which has high pigment protein content, is rich in iron and is effective for preventing anemia. It also contains DHA and EPA, which can lower cholesterol levels and promote brain health. Another characteristic of akami is its “akami” or “bloodline,” which refers to the reddish muscle fibers found between the fish’s back and belly. While both akami and shiromi have bloodlines, akami generally has more, accounting for over 15% of the flesh, while shiromi has less than 10%. The color of the bloodline can be used as an indicator of freshness. It starts as a vibrant reddish-black color when fresh and gradually darkens as the fish ages. Despite its appearance, the bloodline is rich in nutrients, including iron, anserine, vitamin A, and vitamin D, making it a valuable component of the fish. While it may have a slightly fishy odor when raw, it becomes more palatable when cooked or grilled.
Akami Fish Used in Sushi
Now, let’s introduce some of the fish classified as “akami” and commonly used in sushi. Among the most representative akami sushi ingredients, we have tuna, bonito, yellowtail, sardine, saury, and mackerel. As mentioned earlier, fish like sardine, saury, and mackerel may be classified as akami in fisheries science, but in the sushi world, they are considered “hikarimono” or silver-skinned fish, so it’s important not to confuse them.
Tuna
Tuna is undoubtedly the most iconic fish in the akami category. It is a large, carnivorous fish known for its continuous migration in the ocean. Tuna is cherished as a vital seafood not only in Japan but also worldwide. Depending on the part of the tuna, the sushi presentation varies. The belly section, closer to the head, is known as “otoro,” the leaner part on the back is called “akami,” and the intermediate section with firm red meat and some fat is referred to as “chutoro.” In the world of Edo-style sushi, the quality of a sushi restaurant is often judged by the quality of its akami.
Bonito
Bonito, available during spring and summer, is another fish commonly used as akami in sushi. While it has been a popular fish since the Edo period, it was primarily consumed as sashimi due to its perishable nature. It became a sushi ingredient later during the Showa era. Bonito is appreciated for its subtle sweetness, elegant acidity, and refreshing aroma. There are two types of bonito: “hatsugatsuo,” which migrates northward in the Pacific Ocean from spring to summer, and “modorigatsuo,” which returns southward in autumn. Modorigatsuo has higher fat content, resulting in a richer flavor.
Yellowtail
Yellowtail, often mistaken for shiromi due to its pale flesh, is actually considered akami. Yellowtail goes through different names based on its size in the Kanto region: “wakashi” (20 cm), “inada” (40 cm), “warasa” (60 cm), and “buri” (80 cm or larger). In Kansai, “inada” and “warasa” were traditionally referred to as “hamachi.” In recent times, even in Kanto, small farmed yellowtail is commonly called “hamachi.” Yellowtail, like buri, is rich in vitamin D, making it an excellent choice for bone development, especially for children. Yellowtail with ample fat is known for its richness and melt-in-your-mouth texture, similar to otoro.
Hikarimono
Even though fish like sardine, saury, and mackerel are technically akami, they are categorized as “hikarimono” in the sushi industry. Hikarimono is often vinegared to eliminate any fishy odor, and the process of vinegaring is considered a skill that reflects a sushi chef’s expertise. “Aojiru” or “blue fish” is a common term used for fish with a glossy blueish hue in fisheries science, but it’s a separate classification from hikarimono and is mainly used for practical purposes.
In Conclusion
How did you find this article? We’ve explored the world of akami, a cornerstone of sushi. We’ve learned that the red color in the flesh of migratory fish, which characterizes akami, is due to pigment proteins that carry and store oxygen, such as hemoglobin and myoglobin. The classification of fish into akami or shiromi is based on the content of these pigment proteins. We’ve also discovered some surprising examples, like yellowtail being akami despite its appearance and salmon being mistaken for akami when it’s actually shiromi. Akami is not only delicious but also rich in nutrients like iron, anserine, vitamins, and beneficial fatty acids like DHA and EPA, making it a healthy choice for sushi. While some fish are akami in fisheries science, they are considered hikarimono in the sushi world, emphasizing the importance of understanding these distinctions. Comparing the unique flavors of akami, shiromi, and hikarimono can add a new dimension to your sushi appreciation. Enjoy exploring the diverse world of sushi!
