Are local eggs more nutritious?

The just past "3.15 Party" exposed some products as usual, such as e-cigarettes, diapers, toys, free-range eggs, etc.

When it comes to intimacy, the closest thing to our lives is probably eggs. Readers must also have some questions: Are free-range eggs more nutritious? What does the color of the yolk mean? Is there any difference between eating it fried, stir-fried, or boiled?

Today, let’s talk about these things.

Eggs (image source: en.wikipedia.org)

Are local eggs more nutritious?

The nutritional value of eggs goes without saying. In addition to the "life-saving" ingredients such as protein and fat, any nutrient you can think of, including iron, calcium, vitamins, and omega, which has been particularly popular in the past two years, -3 fatty acids are almost always found in eggs.

The question is, will different breeding methods lead to differences in ingredients?

Yes, but not significantly.

Based on the breeding method, eggs can be divided into two categories, caged and non-caged. Cage-raised eggs are the most common eggs. Non-cage-raised eggs are divided into cage-free raising (only there is no cage and the hens have limited space for movement), free-raising (hens can move freely), organic raising, etc.

Among them, organic farming has the highest standards. According to the requirements of the United States Department of Agriculture (USDA), every step of organic farming must be organic. The hens must have sufficient space to move, the feed must be organic products, and antibiotics and other additives are not allowed. However, when it comes to nutritional content, USDA stated that there is currently no definite data to prove that the environment in which hens are raised will cause nutritional differences in eggs.

Of course, researchers have not been idle. A foreign study shows that organic eggs and ordinary eggs are victorious: organic eggs have a slightly higher protein content, while ordinary eggs win in terms of magnesium and iron content.

Comparison of three types of eggs (picture source: academic.oup.com)

Is the yellower the yolk, the more nutritious it is?

In traditional times, this might be the case.

The nutrients in eggs have only two sources: either from the food consumed by the hen, or from the hen's own synthesis. The color of egg yolk is determined by carotenoids, which hens cannot synthesize.

In traditional times, hens were kept free-range and ate whatever they had. The proportion of carotenoids in the diet was not high. That is to say, the yolk is very yellow, which indirectly indicates that the hen is rich in food. Therefore, the nutritional value of the whole egg may be higher. Not so now. In modern breeding technology, the most important thing is to solve the output ratio and try to make the hens eat less and produce more. If the proportion of carotenoids in the diet remains unchanged, the less the hen eats and the less carotenoids it consumes, the lighter the yolk color will naturally be.

So, a contradiction arises. Breeders hope that hens will eat less and give birth to more eggs at the expense of lighter yolk color, while consumers, whether domestic or foreign, still follow tradition and prefer dark yolks. Under such circumstances, some scholars have come up with a compromise solution by adding carotenoids to the feed to artificially interfere with the color of the egg yolk.

Research shows that the rational use of additives can make the color of egg yolk darker without affecting the quality of eggs. But on the other hand, since the color of egg yolk depends on the intake of carotenoids, even if the color of egg yolk is lighter, it does not mean that the nutritional value of eggs is low.

Is there any difference between frying, stir-frying and boiling?

There is a slight difference.

With any cooking method, two aspects must be considered: whether it will destroy the nutrients in the food, and whether it will produce any new or harmful substances.

Specifically when it comes to eggs, first of all, try to eat cooked ones. The protein utilization rate of cooked eggs is much higher than that of raw eggs. Secondly, frying, stir-frying, and boiling will cause certain nutritional losses, but the total amount is not large. , the difference is not big.

So, only in terms of preserving nutrients, the difference between frying, stir-frying and boiling is very small. The key is that frying or stir-frying may use a lot of fat and salt, which may produce harmful substances due to long-term high-temperature cooking. Taken together, cooking and eating is the most ideal.

In short, in recent years, people have become more and more picky about what they eat, but being picky must also follow basic principles. According to existing research, there is no connection between the nutrition of eggs, the way they are raised, and the color of their yolks.

Readers, you can learn about the national testing standards for eggs (GB 2749-2015), regularly check the random inspection results of the State Administration for Market Regulation, and choose your favorite among the qualified products.

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References

[1] Fu Lijun, Zhang Huan, He Linzhi, et al. Research on nutritional differences between northern and southern eggs, eggs of various shell types, foreign eggs and native eggs [J]. Food Industry Science and Technology, 2010, 31(6) : 317320.?

[2]Xu Guiyun. New understanding of egg quality and nutritional value[J]. Chinese Poultry, 2012, 34(13).?

[3]Yin Ruoxin , Sun Xiaojun, Zhou Shiliang. Egg yolk coloration mechanism and influencing factors[J]. Poultry Science, 2014(06): 5052.?

[4]FILIPIAKFLORKIEWICZ A, DERE K, FLORKIEWICZ A, et al. The quality of eggs (organic and nutraceutical vs. conventional) and their technological properties[J]. Poultry Science, 2017, 96(7): 24802490.?

[5]State Administration for Market Regulation[EB/OL] . [2019-03-21]. /nsjg/spcjs/201902/t20190222_291098.html.?

[6]National Organic Program | Agricultural Marketing Service[EB/OL]. [2019-03-21 ]. The signed articles published on this website only represent the author's views and have nothing to do with this website. If there is any infringement, the author will be solely responsible.

Author: Zhao Yanchang