Knowing these things, fish will taste even better!

Foodie Cloud: Those who run on the ground are not as good as those who fly in the sky, and those who fly in the sky are not as good as those who swim in the water...

The main species swimming in this water are fish. Compared with the pork, beef and mutton that we commonly eat, eating more fish is more beneficial to your health.

my country's "Dietary Guidelines for Chinese Residents" also recommends that people eat fish twice a week or 300 to 500 grams of fish per week, averaging 40 to 75 grams per day.

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However, according to the data in the "Chinese Residents' Dietary Guidelines Scientific Research Report 2021", only 25.6% of Chinese adults had an average daily fish and shrimp intake that met the standard or above in 2018, and 74.4% of adults had a daily fish and shrimp intake of less than 40 grams per day. In terms of livestock and poultry meat intake, the proportion of people aged 18 to 44 who consumed ≥ 75 grams of livestock and poultry meat per day was relatively high, at more than 58%.

Therefore, most of us need to pay attention to increasing the intake of fish and shrimp in our diet, while reducing the intake of some livestock and poultry meat.

This article will explain in detail why we recommend eating fish and how to make it delicious. Finally, it will teach you how to choose and buy fish.

01

What are the benefits of eating fish?

Most fish meat is pale white, which is related to the fish's growth environment. Fish live in water and swim every day, so they need a long period of endurance to complete. Water also creates buoyancy and resistance for fish. The faster you swim, the greater the resistance. Therefore, fish also need to have enough power to accelerate. Therefore, fast white muscle fibers that need to reserve emergency energy occupy the vast majority of muscle mass, mainly to facilitate sudden acceleration. Some fish have more red meat. These fish are generally fish that can swim for a long time in one breath, and they have more pink muscle fibers.

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Most land organisms store energy in fat, while fish store energy in the protein in their muscles. Therefore, fish meat contains more protein, generally 15% to 22%, and it is high-quality protein with a high absorption rate.

At the same time, because fish live in water all year round, they need their bodies to maintain normal function even at 0 ℃, so their fat structure is long and irregular, containing more unsaturated fatty acids, mainly n-3 series. Especially fish living in seawater, the content is richer. This fatty acid plays an important role in human health. It is related to the health of the brain and retina, cardiovascular and immune system.

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A diet rich in n-3 polyunsaturated fatty acids has anti-inflammatory effects, can lower blood cholesterol levels, inhibit the formation of blood clots, and reduce the risk of heart disease and cancer.

Studies have shown that consuming more fish can reduce the risk of all-cause mortality and stroke, as well as the risk of dementia and cognitive impairment in middle-aged and elderly people.

In addition, fish liver is rich in vitamin A and vitamin D, which can promote the body's absorption and utilization of calcium, and is beneficial to eye health and can prevent night blindness.

02

When is fish best to eat?

The meat of livestock and poultry that we usually eat takes several hours to reach the mature stage after slaughter, and it is most delicious in the mature stage. Fish is different. Fish matures very quickly after slaughter, and it is more delicious after a short period of time. Some fish will taste more delicious just after the rigor mortis period, which is about 8 to 24 hours after death, but if the rigor mortis period is over, the fish meat will easily spoil. This is why many restaurants have "live fish killed on the spot".

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03

What happens when fish is cooked?

When fish is cooked and heated, its texture, smell, and color change, and these changes make cooked fish seem more appetizing than fresh fish.

① Changes in fish color:

The meat of fish and shellfish is transparent when fresh. When heated, the myoglobin denatures and changes from transparent to white.

It is different for shrimps and crabs. When fresh, they are generally green in appearance. This is because astaxanthin combines with protein to form pigment protein. After heating, the protein denatures and astaxanthin is oxidized into astaxanthin, so they turn red in appearance.

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② Changes in fish texture:

As the temperature gradually rises during the cooking process, the fish meat changes not only in color but also in texture. When the temperature is higher than 60°C, the muscle tissue shrinks, the water content continues to decrease, and the hardness increases.

Fish meat is relatively fragile and can be easily broken if not handled with care. This is because fish muscle is a layered structure, stacked up layer by layer to form a "W" shape, and has a low connective tissue content, which cannot maintain its shape better. During the heating process, the collagen in the connective tissue of fish meat will begin to decompose at 50 ~ 55 ℃, causing the fish muscle to begin to stratify and become sections.

Therefore, fish should be cooked over a low heat and not for too long. If the fish is heated for a long time, it will not only become tough and hard, but also fall apart. A 2.5 cm thick piece of fish will be cooked in about 10 minutes. The thicker parts of the fish can be cut diagonally every 1 to 2 cm to improve the problem of uneven thickness of the fish affecting its doneness.

Someone has done a cooking experiment on bream. 500 grams of bream can be fully cooked in a steamer at 100℃ for 8 minutes, and the texture is just right. If the bream is marinated with an appropriate amount of salt, under the same heating conditions, the meat can be fully cooked and tender in about 9 minutes.

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When cooking fish, first slice the fish into medium-sized fish fillets, put the fish fillets into the pot before the heating soup is about to boil, then turn off the heat, add a little cooled cooking juice, and lower the temperature in the pot to 65 ~ 70 ℃ (you can use a thermometer), cover the lid and let the fish fillets slowly cook through.

③ Changes in fish smell:

Most people think of fish as smelling "fishy". In fact, very fresh fish does not smell fishy, ​​but rather like the smell of plant leaves squeezed out of juice. Almost all fish carry an aroma molecule that can emit a strong geranium leaf scent, with a little metallic taste. Freshwater fish carry the scent of "freshly cut grass" and earthy flavors.

The earthy smell mainly comes from earthiness, which is concentrated in the fish skin and dark muscle tissue. Generally, it can be broken down by using vinegar or other sour seasonings.

The fishy smell mainly comes from trimethylamine. This is because trimethylamine oxide produced by fish to balance the salt concentration of seawater encounters bacteria on the fish's body and is decomposed into trimethylamine with a fishy smell.

To remove the fishy smell, you can first rinse with clean water to wash away the trimethylamine on the surface of the fish. Then use acidic seasonings such as vinegar and lemon to marinate, which can provide hydrogen atoms to combine with trimethylamine, allowing it to combine with water and other molecules, so that the fishy smell will not be emitted into the nasal cavity when we eat fish.

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Although fresh fish generally tastes fishy, ​​the interaction between fatty acids, oxygen molecules, amino acids and other substances will give cooked fish a unique flavor after heating. Raw fish contains more nucleotides, which will have a savory taste after heating. The content of volatile acids, nitrogen compounds and carbonyl compounds in cooked fish increases significantly. These are volatile components, so they make us smell the tempting aroma.

Fish meat processed by grilling, frying, smoking, etc. will have a better flavor. If the fish is brushed with sauce while grilling, the ethanol, soy sauce, sugar and other substances in the sauce will also participate in the thermal reaction, plus the various amino acids and oligopeptides produced by the hydrolysis of fish protein, making the overall smell more coordinated and prominent, and the taste more delicious and rich.

04

What fish are recommended?

Although it is recommended that you eat fish regularly, not all fish can be eaten. Marine fish in particular may be contaminated by heavy metals. The amount of pollutants in fish meat is related to their eating habits and living waters. Large predatory fish at the top of the marine food chain have higher toxin levels.

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Almost all chemicals produced in the world will eventually accumulate in marine organisms. The most harmful ones are dioxins and polychlorinated biphenyls, which can harm our nerves and brain. Organic pollutants can also cause liver damage, cancer and endocrine disorders.

On January 18, 2017, the U.S. Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) released the final version of fish consumption recommendations, recommending eating 227 to 340 grams of low-mercury fish per week, and avoid choosing fish with high mercury content, such as big-ear mackerel, bigeye tuna, marlin, swordfish, New Zealand redfish, etc. As for the specific recommended fish, please see the following figure:

▲Image source: U.S. FDA fish consumption recommendations

In addition, women who are planning to become pregnant, pregnant women, and young children should avoid eating large or predatory fish, such as tuna (especially bigeye tuna and bluefin tuna), alfonsino, shark, swordfish, marlin, orange roughy, and king mackerel, because these fish may contain higher levels of heavy metal methylmercury than other fish.

05

How to choose a good fish?

If you want to eat delicious, nutritious and safe fish, you need to be more careful when buying fish. It is recommended to refer to the following 4 points when buying:

① Look at the fish scales: The scales look fresh and shiny, stick to the fish body and are not easy to fall off, just like armor. This is a fresh fish. For stale fish, the scales have lost their luster, are loose and easy to fall off, and are not firm.

② Look at the fish gills: The gills of fresh fish are clean, bright red, without mucus and odor, and the gill covers and mouths are tightly closed; while the gills of stale fish are dark red, grayish red, or even green or white, with increased mucus and a fishy smell, the gill covers are loose, and the mouth is wide open.

③ Look at the eyes: The eyes of fresh fish are clear and protruding, with distinct black and white; while the eyes of stale fish are sunken, with cloudy eyeballs and a white film.

④ Press the fish body: When you press the body of a fresh fish, it will not dent, will be elastic, and will feel hard. The softer parts will recover immediately after being pressed, and the belly of the fish will not swell. However, when you press the body of a stale fish, it will dent, feel soft, and be sticky. The soft parts will not recover after being pressed, and due to the growth of bacteria, the belly of the fish will swell and its belly door will protrude.

In addition, if you are choosing live fish, those that are lively and responsive are the best. Those that are slow to move or float on the water may be about to die.

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Properly increasing fish intake is good for health, but it is recommended not to eat freshwater sashimi, and eat less grilled and fried fish, because freshwater fish sashimi may be contaminated by parasites and bacteria , and grilled and fried fish may produce carcinogens.

References:

[1] Chinese Nutrition Society. Dietary Guidelines for Chinese Residents[M]. People's Medical Publishing House. 2022

[2] Harold Mackey, author. Translated by Lin Huizhen. Food and Cooking. Milk, Eggs, Meat, Fish. Beijing Fine Arts Photography Publishing House. 2013.8

[3] Zhou Xiaoyan. Cooking Technology[M]. China Textile Press, 2008.

[4]https://www.fda.gov/food/consumers/advice-about-eating-fish

[5] Centre for Food Safety, Government of the Hong Kong Special Administrative Region https://www.cfs.gov.hk/english/multimedia/multimedia_pub/multimedia_pub_fsb_201404.html

Author | Xue Qingxin, member of Chinese Nutrition Society, registered nutrition technician, health manager, public nutritionist

Review | Chen Shengjun Associate Researcher, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences

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