Common cooking methods of eggs
However, if eggs are not cooked properly, their health benefits may be offset by their shortcomings.
Almost every family eats eggs, ducks and eggs. How is it made? There are several common home cooking methods:
A whole boiled egg b boiled poached egg c fried poached egg d scrambled egg e steamed egg soup
In addition, restaurant practices are different, such as egg yolk _ pumpkin, fried egg jiaozi, and all kinds of dishes wrapped in egg skin. These dishes are delicious, but will their cooking methods cause health problems?
Changes of nutritional components during egg cooking
To answer this question, let's first talk about what unhealthy changes may occur in egg cooking.
Vitamin destruction
People often think of "vitamin destruction" first, such as vitamin B2, vitamin B6, vitamin A, etc. Egg yolk is rich in vitamins. However, the measurement data of USDA show that the changes of these three vitamins are not great for several cooking methods commonly used in families because of the relatively short heating time.
In terms of protein's digestion and absorption rate, there is little difference between steaming, boiling, frying, frying and other cooking methods if they are not fried until they are crispy.
However, don't worry about hearing this, be happy. Because there are some health indicators that people usually don't know-cholesterol oxidation, fat oxidation and glycated protein product formation, as well as fatty acid ratio and fat content. These new research indicators make us pay new attention to the study of cooking nutrition.
Cholesterol oxidation products
As we all know, egg yolk is rich in cholesterol. In fresh eggs, these cholesterol are closely protected, oxygen is not seen, and it will not be oxidized. Therefore, the determination shows that the oxidation degree of cholesterol in eggs just a few days old is almost zero. However, as time goes on, cholesterol gradually begins to be oxidized. But the proportion of oxidation is still very low, because it is protected by eggshells and egg whites after all.
When cooking is heated, the oxidation degree of fat and cholesterol in eggs will increase. The longer cooking time, the greater the loss of vitamin E and the more oxidation of fat and cholesterol, as I said in my previous blog post. A study in Taiwan Province Province found that when making tea eggs, the content of cholesterol oxidation products in tea eggs increased with the extension of heating time within 0 to 24 hours of heating and marinating time. However, soy sauce and tea itself are not the culprit of oxidation. On the contrary, they can provide antioxidants and reduce the oxidation of eggs, so the processing method of boiled tea eggs is reasonable.
Comparatively speaking, boiled eggs are the most closely protected and have the least contact with oxygen; After the eggs are opened, the oxidation degree of fat and cholesterol will increase obviously. It is found that if eggs are made into yolk powder, the severity of oxidation will increase significantly; Or make eggs into salad dressing, an emulsified product, which has more contact with oxygen and more serious oxidation. It was found that the oxidation of cholesterol in mayonnaise became more and more serious with the extension of storage time.
The same is true of cooking. Compared with boiled eggs, scrambled eggs have a higher degree of fat oxidation and cholesterol oxidation. If the spread egg skin is fried in oil again, obviously the degree of oxidation will be higher. _ The practice of salted egg yolk has not yet been determined, but it is undoubtedly the worst of all cooking methods-salted egg yolk has been oxidized in the production process, and then directly stir-fried in hot oil at high temperature, fully exposed to the air, which is simply the best condition for making oxidized cholesterol and oxidized fat!
I always stay away from such dishes. I have psychological barriers. I always feel that the taste is the smell of fat oxidation.
Then maybe friends will ask, what harm does this oxidized cholesterol and oxidized fat have? At present, it has been found that cholesterol oxidation products can cause vascular endothelial damage, arteriosclerosis and DNA damage, thus increasing the risk of mutation and carcinogenesis. Cholesterol oxidation products in food will be absorbed by the human body like normal cholesterol, combined with lipoprotein, sent to the liver and then sent to all parts of the body. As for the harm of fat oxidation products to promote the production of free radicals, people have long understood. Think about these "poisoned" cholesterol and fat flooding the body, how can it be psychologically comfortable?
Glycosylated protein products
Another recent concern of the scientific community is the "glycated protein" products formed in food cooking. This glycated protein may be familiar to friends with diabetes. If the blood sugar level remains high for a long time, protein glycated products in the body will increase. If the glycated protein index is determined, the index will increase obviously. Glycosylated proteins are closely related to human aging and multiple organ damage. But there are many glycated protein products in food, which people may not know.
In fresh eggs, the content of glycosylated protein is very, very low. However, the determination shows that the content of glycosylated protein will increase to 30 times after the eggs are fried. What if you cook the eggs whole? The content of glycated protein has hardly increased, just like raw eggs before cooking. It is found that any food containing protein, or food rich in protein and oil, will easily produce a large number of glycated protein products after high-temperature cooking.
Some people may ask: How is the glycated protein in fried eggs formed? Where is the sugar? Fried eggs don't contain sugar, and eggs themselves don't contain sugar! Yes, this is because fat will be oxidized at high temperature. The products of fat oxidation, like sugar, all contain carbonyl groups, which can replace sugar and react with protein to produce glycated protein.
From the point of view of fat content and fatty acid ratio, it is naturally the best way not to use or use less edible oil. Scrambled eggs will introduce a lot of omega-6 oil, while the whole boiled eggs, poached eggs and steamed egg soup will hardly increase the fat content.
In a word, the fat, cholesterol and protein in eggs have no obvious harm to human body before being oxidized. However, after improper cooking, fat and cholesterol are oxidized to produce glycated protein products, which may have a potential impact on human health. Especially after the body's metabolic capacity declines, it is possible to deal with these unfavorable components in time, which is likely to become a hidden danger of the disease. Nutritional epidemiological investigation found that eating too many eggs was unhealthy did not take into account the cooking methods of eggs. I hope future research can make up for this deficiency and see if boiled eggs, scrambled eggs and fried eggs are harmful to health.
Ranking of healthy eating methods of eggs
Speaking of this, friends who are tired of listening to new scientific vocabulary can catch their breath and listen to me sum up the relationship between egg cooking methods and health.
According to the degree of oxidation and heating, the methods of cooking eggs are arranged as follows:
A-class boiled eggs with soft yolk.
B-class poached eggs and egg drop soup
C-class tender steamed eggs and fried eggs.
D scrambled eggs, fried eggs, egg pancakes.
E-class fried egg horn, boiled egg skin, etc.
F _ egg yolk, all kinds of fried foods with egg liquid on the surface.
Speaking of which, it really makes me happy to think of a conversation that happened in my kitchen.
One day, my husband cooked, steamed the eggs with an egg cooker, then cut them into pieces and poured a little sauce on them. I asked: Why not make scrambled eggs? He said: scrambled eggs have oxidized cholesterol! I'm surprised. how do you know He said, didn't you say it on TV? In the past, he was quite willing to fry eggs with oil and fry them a little older. Now it's really gratifying that he will be completely changed because of the word oxidized cholesterol.