Everything You Need to Know About Maguro Tuna – A Beginner's Guide

Maguro (tuna) is always the No.1 popular fish in Japan, but with the global rise of health consciousness, this fish is gaining huge popularity all over the world. Although it is true that maguro is a standard fish ingredient used in sushi, defining it as “a fish that is the most familiar fish in sushi bar” will not allow you to truly understand the whole picture of it. Therefore, this article will explore tuna in greater detail by focusing on the following elements:

• Basic information on maguro
• Maguro species
• Health benefits of maguro
• Culinary guides of maguro
• Tips to identify delicious maguro
• How to thaw maguro successfully

What is Maguro?

Maguro, also known as tuna, is a familiar edible fish that belongs to the mackerel family in its biology classification. Most tuna are massive in size, can swim fast over a wide range of ocean, are higher intermediate predators in the food chain of the sea, and have a streamlined body. Depending on the types of tuna, they are usually 2 ~ 3 meters large, 100 ~ 300kg heavy, and can swim up to approximately 80km (almost equal to 49.7mph).

Easily available at most supermarkets and restaurant chains, maguro is one of the most commonly eaten fish in Japan that commonly appears on the dinner table. Besides Japan, the US, EU nations, East Asian nations including China, South Korea, and Taiwan are also major consumers of this fish, but recently consumption is also rising in other regions such as South Asia, South America, and Southeast Asia. This means tuna is no longer a delicacy unique to Japan.

What makes maguro quite different from other fish is that it has totally different tastes and textures according to its parts. For instance, the belly flesh is usually called toro, and has a very rich flavor; in contrast, tuna’s back flesh is referred to as akami (red flesh), which is less fatty than toro but has a meaty yet smooth texture.

Types of Maguro

Even though maguro is often eaten by Japanese, that does not mean they always eat the same kind of maguro. Likewise, not all kinds of tuna are suitable for sushi or sashimi. This section introduces maguro that are commonly distributed in Japanese markets.

Kuro-maguro / Bluefin Tuna

Kuro-maguro is the largest species in the tuna category where an adult tuna is about 3 meters large and weighs between 300 ~ 600kg. It is said that Kuro-maguro (also called Hon-maguro) has two different categories: Pacific bluefin tuna and Atlantic bluefin tuna, and in Japan the former is more consumed. No tuna can match the tastiness of Kuro-maguro’s toro, but a beautiful dark red akami is also tasty.

Nicknamed the black diamond, a wild kuro-maguro is considered to be the highest-class fish. In fact, at the first auction in a Japanese fish market in 2019, the highest winning bid of this tuna was 333.6 million yen (approx. US$2.75 million), which was the highest price ever sold at the first annual auction. FYI, it was 16.88 million yen (approx. US$138,000) at the first auction in 2022.

Minami-maguro / Southern Bluefin Tuna

Minami-maguro is literally caught in the seas of the Southern Hemispheres and is another popular type of tuna in Japan because its toro flesh is as tasty as that of hon-maguro. Since this fish also has otoro (extra fatty belly flesh), it is regarded as a luxury fish in the market and highly valued as a high-grade sushi ingredient. Minami-maguro’s fatty flesh features a distinctive flavor with strong viscosity while the akami has a slight sweetness.

Mebachi-maguro / Big-eye Tuna

Mebachi-maguro is a middle-class tuna that has big eyes, large pectoral fins, and yellow dorsal fins. Most of its flesh consists of a mild-flavored akami, so it is very easy to eat and favored by akami lovers. Unlike hon-maguro and minami-maguro, it has little toro, if any, and is stringy in texture, making it unsuitable for raw consumption. For this reason, mebachi-maguro’s toro is often used for processed foods.

Kihada-maguro / Yellowfin Tuna

Kihada-maguro literally translates as “yellow skin tuna” because not only its fins but also its skin is yellowish. Although its flesh is tougher than other species, this maguro is also commonly consumed in Japan. Cheap in price and rich in protein, this fish is gaining more popularity among health-conscious consumers.

Binnaga-maguro / Albacore Tuna

This maguro is totally different from other species; it has very long pectoral fins and a pale pink flesh that has both sweetness and a mild-acidic flavor. As a sushi ingredient, it is often consumed in revolving sushi restaurants because of its low price. Besides sushi use, binnaga-maguro is regarded as a premium ingredient of canned fish such as “Sea Chicken'', and the flesh remains soft even when cooked sufficiently.

Health Benefits of Consuming Maguro

Like many other fishes, maguro brings many health benefits but you should note that nutrition varies between the parts of flesh. In this section, we have divided the maguro flesh into three categories: akami, toro, and chiai.

Akami (red flesh)

Usually located on the backside of maguro, akami is high in protein and low in fat, so it can be a fine substitute for meats. Akami is also rich in selenium, an insoluble and highly antioxidant mineral that increases your immunity and prevents aging. Akami is the least fatty part of the tuna flesh, but includes a natural umami and smooth texture.

Toro (fatty flesh)

In Japan, toro is loosely classified into chutoro (fatty belly) and otoro (extra fatty belly). Chutoro is a hybrid of akami and otoro: its taste is a harmony of umami and sweetness, and the texture features smoothness of akami and melty feeling of otoro. In contrast, otoro is usually pink with a white fat marbling like wagyu beef, and has a super rich taste that instantly melts in your mouth. Chutoro flesh is located on the back and belly close to the tail, while otoro can be found on the frontside of the belly.

Although toro is high in fat content, it is much healthier than fatty meats because it is a rich source of omega-3 oils like DHA and EPA, so by consuming it you can decrease neutral fat and blood clots in your blood. Toro fat can also mitigate the risks of high-blood pressure, arteriosclerosis, and dyslipidemia. In addition, toro contains more vitamin A and E than akami, and these are helpful in preventing dementia and increasing learning ability.

Chiai (dark flesh)

Chiai is located between the belly and back; however, few Japanese tend to want to consume it because of its distinctive bloody odor. However, this flesh is very rich in iron, taurine, and vitamin B, so it’s a great natural supplement, which is effective against anemia, arteriosclerosis, as well as alleviating hangovers and lifestyle-related diseases.

If you wish to try chiai, it is highly recommended to cook it instead of eating it raw. To do so, boiling is the best way to make it easier to eat. Lightly rinse the chiai flesh with water, then boil it for about 5 minutes. For better results, add some sake or white wine and grated ginger to the water before boiling it.

Overall, maguro is a healthy food and this feature might be one of the reasons it is consumed globally. However, like other seafoods, you should note that over-consumption of maguro may lead to an accumulation of heavy metals like mercury. Although it depends on how you eat maguro, avoid eating more than 100g per meal or consuming it more than once a week.

How to cook / eat Maguro?

If you are not familiar with maguro, you may try it first with either sashimi or sushi. When doing this, try akami, chutoro, and otoro at once and compare their taste, texture, and umami. The tuna flesh with and without soy sauce has different flavors, so try both and find your favorite flesh part and seasoning.

If you are eating the maguro that does not have much toro, it is best to enjoy it by eating it as a steak or simmered dish. Smooth and light in flavor, canned tuna is easy to eat as it is, and it goes nicely when added to a salad or pasta. In short, if the maguro is fatty, try raw sashimi, and if not enjoy it with a cooked meal.

How to select quality Maguro?

You may find in either a bar-shaped block (this is usually called saku), or sliced maguro at the supermarket near you, but it can be disastrous if you fail to choose a fresh and tasty one. In this section, we will provide some tips to identify high-quality maguro.

The following image shows three different saku blocks of maguro; which saku do you think is the most delicious? All of these are the same maguro akami, but each has a different muscle pattern: parallel, diagonal, and V-shaped like a woodgrain, and by looking at this pattern you can choose the quality of maguro before you eat it.

Anyway, the answer is A. For maguro, the less and thinner tendons it has, the tastier it is. These muscle patterns make it tricky to slice because the kitchen knife gets stuck when it touches these white objects. The maguro with too many tendons or their pattern being too complex (like C in this case) tends to have a stringy texture. For B, its quality is not as good as A, but it is considered to be fine in quality. Here are other tips to find good tuna:

Color – fresh tuna has a bright red color (if bincho-maguro, it is pale pink) with a slight translucent gloss. When maguro loses its quality, the color turns brown or white and has a little dewiness.

Muscle patterns – as mentioned, find a maguro block that has parallel or diagonal muscle patterns. Also, avoid choosing saku that has too many and/or thick tendons.

Spots – when you find the saku with red or black dots on its surface, that is a sign of low quality maguro. These are a blood clot and it is generated if a blood removal is insufficient. Such a spotty maguro usually smells unpleasantly bad, so keep an eye on each saku.

Drip – just like other fish, avoid buying the maguro if there is a pool of drip on the tray. This liquid consists of umami and it will appear if the flesh has been thawed for a long time. In other words, fresh maguro will not have such a leakage.

How to Thaw Maguro?

If the supermarket near you sells frozen tuna only, you will have to defrost it. But using the wrong method (e.g. thawing at room temperature or using a microwave) will significantly decline the quality of maguro. It is said that there are two ways of thawing, namely salt water thawing and ice water thawing. Let’s begin with the salt water method.

Salt Water Thawing

1. Wash the frozen maguro with tap water. Do not rinse too much or you may wash off its umami.
2. Prepare a tray or bowl filled with lukewarm water saturated with approximately 30 ~ 40g of salt. The recommended water temperature is between 35 and 40℃.
3. Let the maguro soak in the salt water for 3 ~ 4 minutes. Gently rub the surface of the maguro to remove residues of ice crystal and tiny maguro chips.
4. Remove the saku from the salt water and pat dry with paper towels. Make sure to dry it thoroughly and immediately.
5. Wrap the maguro in paper towels and place it in a zip-locked bag. Then refrigerate it for 1 ~ 2 hours.

Ice Water Thawing

Next is the ice water thawing. Although this approach takes longer than the salt water method, it has a lower risk of failure:

1. Wash the frozen maguro with tap water. Do not rinse it too much or you may wash off its umami.
2. Fully dry any moisture and remove icy residues from the maguro block with the kitchen paper.
3. Place the dried block inside a resealable freezer bag. Make sure to seal it tightly and remove all the air from it.
4. Place the bag in the bowl or tray filled with ice water. Do not let the maguro float: weigh down the maguro by putting some refrigerant packs on it. Thaw it for 60 ~ 75 minutes.
5. Take the maguro from the freezer bag and dry it thoroughly again. Wrap the block in fresh paper towels. Then refrigerate it for 6~ 8 hours (if possible, half a day).

When you see the flesh after thawing, you may find it slightly smaller than it was, which is called chijire (literally means “shrinking”). The trick is that when tuna is caught, it will get quick-frozen to maintain its freshness before rigor mortis. When you thaw such a maguro, this phenomenon starts because the cells in the flesh become active while thawing. This is natural to any fish in the thawing process, and it is a sign of freshness. Therefore, if you find your maguro has become smaller, that means you have successfully chosen the right saku.