Why are duck eggs always pickled? The reason is...

I believe many people like to eat salted duck eggs. The egg white is soft, the yolk is oily, and the sand is delicious... It's really delicious! Even if there is no dish, you can directly "show off" two bowls of salted egg yolk mixed with rice.

Why are duck eggs always pickled, while salted chicken eggs and goose eggs are rarely pickled? This article will answer this question.

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Why are "salted duck eggs" so common?

The taste and flavor of pickled eggs are very different from before, with a strong aroma. This change in flavor mainly comes from the egg yolk. The reason why many people love salted eggs is because their yolks are so delicious! To pickle salted eggs, you must first choose eggs that can make the yolks taste the best. Duck eggs have an absolute advantage because the fat content of duck egg yolks is higher than that of chicken and goose eggs.

Comparison of egg yolk fat content in common egg types

1. Duck egg yolk: fat content 33.8 (g/100g)

2. Egg yolk: fat content 28.2 (g/100g)

3. Goose egg yolk: fat content 26.4 (g/100g)

The reason why we don't see the oily boiled eggs we usually eat is that the egg white and fat in the egg yolk form an emulsified system, and the oil is not visible on the surface. The pickling process causes the hydrophobic groups to separate from the hydrophilic and lipophilic groups in the egg yolk, destroying the emulsified system , and the small oil droplets gather together, which becomes "rich in oil" visible to the naked eye.

When pickling salted duck eggs, salt penetrates from the eggshell membrane into the interior of the egg and gradually seeps into the yolk, destroying the low-density lipoprotein structure of the yolk, which is a necessary condition for the formation of oil exudation.

As the pickling time increases, the yolk loses water gradually, providing a more favorable environment for lipid molecules to aggregate and form oil droplets. The dehydration of the yolk and the combination of protein gel make the yolk eventually become a spherical aggregate. This is the main reason why the egg white of the pickled salted egg is liquid, while the yolk becomes a solid ball with an orange-red color.

During the pickling process, the egg yolk particles will gradually become smaller, arranged more closely, and cross-linked, which is the main reason why pickled salted egg yolks have a special loose and sandy feeling.

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One of the main reasons why duck egg yolks are made into salted duck eggs is that they are rich in fat . Another reason is that boiled duck eggs are not as delicious as boiled eggs. Duck eggs have a fishy smell , which is more obvious than the fishy smell of eggs. Many people don't like to eat them. This is mainly because of the trimethylamine contained in them. Jingjiang duck eggs have the strongest fishy smell. Since they are not delicious when boiled directly, they are simply pickled.

In addition, ducks often lay large numbers of eggs in a concentrated manner. If they lay too many eggs, humans cannot eat them all , so they can only be pickled, which is easier to preserve.

Are there any nutritional changes after duck eggs are “pickled”?

Everyone knows that the salt content of duck eggs will inevitably increase after they become salted duck eggs , and other nutrients will not remain unchanged. The content of calcium, iron and zinc will increase significantly .

Calcium : The calcium content of salted duck eggs is 118 mg/100 g, which is nearly twice that of ordinary duck eggs .

Iron: The iron content of salted duck eggs is 3.6 mg/100 g, which is 1.2 times that of ordinary duck eggs.

Zinc: The zinc content of salted duck eggs is 1.74 mg/100 g, which is 1 times that of ordinary duck eggs.

Magnesium : The magnesium content of salted duck eggs is 30 mg/100 g, which is 2.3 times that of ordinary duck eggs .

The reason for this change is that fresh duck eggs have a high water content, which can reach 70.3%. When pickling salted duck eggs, due to the high osmotic pressure of the salt water, the water will move from the inside of the eggshell to the outside of the eggshell, and the water content of the pickled salted duck eggs is only 61.3%.

The water content in duck eggs gradually decreases, which plays a certain concentrating role, and some nutrients will also be concentrated .

However, don't eat more salted duck eggs just to supplement your nutrition, after all, the salt content is very high. One salted duck egg can take in 3 to 5 grams of salt, which is almost close to the upper limit recommended by the "Dietary Guidelines for Chinese Residents" (no more than 5 grams of salt per day) . If you still have to eat other dishes, the salt intake is easy to exceed the standard. Long-term consumption will increase the risk of high blood pressure, gastritis, stroke and other diseases .

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How are salted duck eggs pickled?

Pickling salted duck eggs is a technical job. Pickling for too long may make the egg white very salty, while not enough pickling time or salt concentration will not give you the desired taste . Generally speaking, there are three methods for pickling salted duck eggs: high-salt pickling method, low-salt pickling method and plastic wrap pickling method .

1. High-salt pickled eggs : Take fresh duck eggs, clean them and dry them → put the duck eggs into a pickling jar → pour in 18% salt solution → seal → pickle at 20~25℃ for 30 days.

2. Low-salt pickled eggs : Take fresh duck eggs, clean them and dry them → Put the duck eggs into a pickling jar → Pour in 18% salt solution → Seal → Pickle at 20-25℃ for 10 days → Replace 18% salt solution with 6% salt solution → Seal → Continue pickling at 20-25℃ for 25 days.

Note: During the pickling process, some high-proof liquor is usually poured in for sterilization.

Of the two methods mentioned above, the high-salt pickled eggs method seems to be simpler, but studies have shown that low-salt salted eggs can more effectively protect the degradation of protein, maintain the hardness and elasticity of protein, and improve the flavor, sensory and nutritional quality of protein .

3. Plastic wrap pickling method : Wash the duck eggs and dry them, soak them in high-proof liquor for a while to disinfect them, then roll them in a bowl of salt to make the duck eggs covered with salt, finally wrap the duck eggs tightly with plastic wrap, place them in a cool place, and pickle them for about 1 month.

How to choose salted duck eggs?

Although some friends like to eat salted duck eggs, they are too lazy to pickle them themselves, so they just buy ready-made ones, which are convenient and delicious. Here are some tips for choosing salted eggs for you to refer to when buying!

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1. Look at the appearance

Choose salted duck eggs with green, intact, crack-free shells and smooth, round surfaces . If the shells are gray, have black spots or cracks, they may have gone bad and are not recommended for purchase.

2. Shake it

If you buy raw salted duck eggs, you can shake them gently in your hand and you will feel a slight vibration . If there is a strange sound like water inside, it may have gone bad.

3. Purchase through formal channels

In the past, there have often been incidents where illegal additives such as Sudan Red were detected in salted duck eggs. It is recommended to go to larger regular supermarkets to buy salted duck eggs produced by regular manufacturers to better avoid such incidents.

Salted duck eggs with rice are simply amazing! But you have to control the frequency. For the sake of health, don't eat it every day!

References

[1] Yang Yuexin. Chinese Food Composition Table 6th Edition Volume 2[M]. Peking University Medical Press, 2019

[2] Wang Yiting, Pang Min. Research on the mechanism and method of pickling salted duck eggs[J]. Modern Food, 2020(22):52-54.DOI:10.

[3] Chen Yanhong, Wang Xiujun, Yu Pei, et al. Analysis of yolk coagulation changes during salted duck egg pickling process[J]. Journal of Chinese Institute of Food Science and Technology, 2023, 23(04): 377-389. DOI: 10.16429/j.1009-7848.2023.04.035.

16736/j.cnki.cn41-1434/ts.2020.22.015.

[4] Li, Xingzheng et al. "Analysis of fishy taint in duck eggs reveals the causative constituent of the fishy odor and factors affecting the perception ability of this odor." Poultryscience vol. 98,10 (2019): 5198-5207. doi:10.3382/ps/pez260

[5] Wang Qian, Qiu Jing, Zou Ligen. Analysis of differences in egg white protein characteristics before and after pickling of duck eggs[J]. Food Science and Technology, 2023, 48(04): 70-74. DOI: 10.13684/j.cnki.spkj.2023.04.001.

Author: Xue Qingxin, China's registered nutritionist, one of the first nutrition instructors of the National Health Commission, and a popular science expert on China's food nutrition and health action

Review丨Zhong Kai, Director of Kexin Food and Information Exchange Center