An egg is an egg without a shell, and its outer layer is covered with a gelatinous substance, such as frog eggs or toad eggs. Generally, mammalian eggs are not excreted for fertilization, so they are called eggs. At a proper temperature, the fertilized egg will hatch in a certain time, and the larva will break out with the keratin above the mouth. Most bird eggs are pear-shaped, that is, one end is pointed and the other end is big. This is to make the whole egg heat evenly when the parent bird hatches the egg, so as not to let the egg roll out of the nest and evolve into that shape, but to roll to the tip.
Eggs have an air chamber at the end of the big head for oxygen exchange and easy breathing. So there are countless pores on the surface of eggs. Protein is as protective and stable as amniotic fluid, while yolk provides nutrition for embryo growth.
Eggs are rich in protein, fat and vitamins, and are one of the important foods. Often eat eggs, duck eggs, pigeon eggs, quail eggs, etc.
Can be made into steamed eggs, baked eggs, fried eggs, preserved eggs.
Foods include egg tart, tempura, double-skin milk, preserved egg crisp, cake, egg drop soup, four-color eggs, preserved eggs, salted duck eggs, tea eggs and so on. There are two white cords on the left and right sides of the yolk, namely the egg lacing, which is a part of protein and a source of high-quality protein. It also contains a component found in bird's nest, called sialic acid, which has antioxidant effect and can be combined with viruses invading human body, thus eliminating viruses, preventing infection and preventing cancer.
In addition, China's ancient medical book Compendium of Materia Medica records that eggs are sweet and flat, which can calm the five internal organs and calm the nerves; It can stop convulsion and prevent miscarriage, and has the effects of nourishing yin, strengthening spleen and tonifying lung. , but also dry. If eaten regularly, it can eliminate illness and prolong life. It is most suitable for growing children, teenagers and pregnant women as nutritional supplements.
Egg nutrition is big PK
Although the nutrition of eggs is slightly focused, the overall difference is not big, and some folk claims lack scientific basis. Let's take eggs as an example to PK and make you a wise man:
1. Red shell eggs and white shell eggs
The color of eggshell is mainly determined by a substance called eggshell porphyrin. The metabolism of heme in the blood of ordinary hens can produce eggshell porphyrin, so the eggshell can be light red, while Hangji and Bailuoke chickens can't produce eggshell porphyrin, so the eggshell is white, which is completely determined by genetic genes.
The nutritional content of eggs mainly depends on the nutritional structure of feed and the feeding situation of chickens, and has little to do with the color of eggshells. The researchers analyzed and determined the components of red-shell eggs and white-shell eggs, and found that the contents of several main nutritional components were different from each other, with little difference, and there was basically no difference between good and bad.
2. Tea eggs
Although tea has a certain health care function, if it is mixed with eggs, it will not only reduce its nutritional value, but also stimulate the stomach. The cosmetic effect of Centella asiatica will affect the digestion and absorption of nutrients for a long time, which is not conducive to health. Especially those suffering from malnutrition, gastric ulcer and iron deficiency anemia. It is not advisable to eat tea eggs.
3. preserved eggs
After fresh eggs were processed into preserved eggs, the most important vitamins with the greatest nutritional loss, such as vitamin B 1, decreased by 70%, and niacin decreased by 50%. Only the contents of iron and selenium in minerals have increased.
In addition, a preserved egg may be contaminated by lead, so it is not advisable to eat more meals.
Pickled eggs
The nutritional value is good, but the disadvantage is that it has been peeled and is easily contaminated by bacteria. It is best to heat and disinfect before eating.
5. Salted eggs
The nutritional value is basically the same as that of fresh eggs, but the content of minerals such as sodium, calcium, iron and selenium is higher than that of fresh eggs. The disadvantage is that the sodium content is obviously increased. The salt content of each salted egg is more than 6 grams, and you can only eat 1 egg at most a day. 6. nutritious eggs
It refers to making a special feed with trace elements such as iodine, zinc and iron. After eating for about two months, the chicken will undergo biotransformation in the body, and the eggs produced are different from ordinary eggs, and the trace elements contained in them are greatly increased.
From a medical point of view, this kind of egg is only suitable for people who lack these trace elements, and healthy people should not eat it indiscriminately, otherwise it may break the balance of trace elements in the body. Eggs, duck eggs, goose eggs ... different kinds of eggs are actually similar in nutrition. However, Chinese medicine believes that there is a great difference between the two in diet therapy.
Eggs and eggs are flat, can replenish qi and blood, and have the effect of calming the nerves and nourishing the heart. Eating eggs when you are sick can restore your strength. Eggs do not harm the spleen and stomach, and are suitable for most people. They are ideal foods for infants, pregnant women and patients. Quail eggs are also sweet and flat, which can invigorate qi and nourish blood, similar to eggs.
Duck eggs are cool, which can clear fire and clear lung heat. It is most suitable for dietotherapy for people with yin deficiency and excessive fire, and can treat symptoms such as hot cough, chest tightness, sore throat and toothache. Can be fried, can be boiled, can be boiled with sugar.
Goose eggs are warm, which Chinese medicine believes can greatly tonify the five internal organs, and are suitable for patients with chronic nephritis, hepatitis and chronic diseases. Eating goose eggs in cold weather can nourish the body and resist the invasion of cold climate.
In short, choose eggs according to your physique. Eggs are suitable for all ages, and 1 ~ 2 eggs a day are suitable for long-term consumption; Duck eggs are suitable for people who are angry and hot; Goose eggs contain an alkaline substance which is harmful to internal organs. Don't eat more than three eggs a day. Boiled eggs are the best way to eat. Fried eggs will lose a lot of vitamins. It is best not to eat immature eggs. Healthy eating method
Although there are many ways to eat eggs, we should also pay attention to whether we eat them correctly, otherwise we will not get nutritional supplements, and may also affect our health. When eating eggs, if you can cooperate with the following healthy eating methods, you can not only reduce the absorption of cholesterol, but also make more effective use of the nutrition of eggs:
1. Eggs contain various nutrients except vitamin C, so if they can be eaten with vegetables, the nutrition will be more balanced.
2. When eating eggs, eat more vegetables, which will help the vividness of vegetables, absorb harmful substances such as cholesterol and excrete them, and reduce the harm of cholesterol.
3. Eggs are difficult to digest raw, and may be eaten by salmonella, fungi or parasites, so it is not suitable for eating eggs raw.
Washing raw eggs with hot soybean milk will form substances that are not easily decomposed and absorbed, which will affect digestion and destroy nutrition.
You can get all kinds of essential amino acids by eating an egg with rice and pasta every day, so you don't need to eat too many eggs a day.
6. When cooking eggs, you can add some traditional Chinese medicines according to your personal needs, such as medlar, red dates, Polygonum multiflorum, Chuanxiong, Artemisia argyi, motherwort, etc., which will have more therapeutic effects.
7. The color of eggshells has nothing to do with the nutritional value of eggs, so you don't have to deliberately eat earth eggs with reddish-brown eggshells.
8. Eating fertilized eggs may not be more nutritious than unfertilized eggs, because unfertilized eggs will not consume nutrition due to embryonic development and are more nutritious.
9. Eggs with scattered yolk can't be eaten, because they may be stored for too long and have been parasitically decomposed by bacteria, so the yolk will be scattered.
10. The color of the yolk has nothing to do with its nutritional value, so you don't have to eat eggs with red yolk.
Matters needing attention
cholesterol
Eggs contain high cholesterol, which is considered to increase blood lipids and lead to arteriosclerosis, so it is generally known that people with coronary heart disease, hypertension, hyperlipidemia, high cholesterol and other diseases should not eat more eggs.
However, some medical studies believe that egg yolk is rich in lecithin, which is a strong emulsifier, which can make cholesterol and fat particles smaller and suspended, which will help lipids penetrate the blood vessel wall and be absorbed and utilized by tissues, thus reducing cholesterol in the blood. Therefore, the medical profession suggests that people who are already ill and need to limit cholesterol intake should control the intake of egg yolk under the guidance of dieticians. The general public, while eating eggs, must control the intake of animal fat and calories, eat more fruits and vegetables to avoid high cholesterol.
bacterial poisoning
In the process of egg production, transportation and storage, if the hygienic quality control is not done well, it may provide a good opportunity for the breeding and reproduction of salmonella, Vibrio enteritidis, Staphylococcus aureus and other bacteria. Eating eggs infected with bacteria can cause vomiting, diarrhea, abdominal pain and fever.
Antibiotic residue
Antibiotics can promote the growth of chickens and increase the chances of laying eggs, but if excessive antibiotics remain in chicken or eggs, it will do harm to health. When buying eggs, please pay more attention to the following items to avoid buying "bad guys":
1. If the eggshell is damaged, it may have bred bacteria and is not suitable for purchase.
2. Try to choose eggs marked with CAS quality eggs.
3. Choose washed eggs that have completely removed dirt and bacteria from eggshells.
It is best not to buy traditional chicken manure, dirt and rice eggs.
5. Newborn eggs, the eggshell is wet, the cuticle is not dry, and it is easy to be invaded by bacteria such as Salmonella and Staphylococcus aureus. It is best not to buy it immediately.
6. The rounder the shape of an egg, the bigger the yolk inside.
7. The rougher the eggshell, the fresher the egg.
8. If you put an egg in 4% salt water, it is a good egg that will sink immediately.
9. The bigger the air chamber of an egg, the worse the quality.
10 preserved eggs with high lead and copper content will have more spots on the eggshell surface. After shelling, you can also see that some parts of protein are dark green or occasionally have black spots, which is not suitable for purchase.
1 1 preserved eggs made by traditional methods, some of which are covered with red soil and straw, are actually unsanitary, and it is not convenient to judge the lead content by appearance, so they are not suitable for purchase. Safe storage and release
Eggs are rich in protein. If stored improperly, they will soon go bad and rot. Therefore, after the eggs are bought back, it is best to store them in the following ways in order to eat them safely and healthily:
1. If you buy ordinary traditional eggs in bulk, be sure to thoroughly clean and dry them before putting them in the refrigerator.
2. The shelf life of packaged washed eggs sold in supermarkets is about 14 days.
Generally, fresh eggs with shells can be kept in the refrigerator for about 7 days in summer and about one month in winter.
Eggshells are afraid of moisture, so they should not be confined in airtight plastic boxes to avoid being damp and moldy.
5. When laying eggs, the rounder end should be upward and the sharper end should be downward.
6. The freezing point of eggs is -2.2 degrees Celsius. If the refrigerator temperature is lower than this temperature, the eggshell may break and the eggs will be polluted.
7. After the egg is shelled, it is best to cook it immediately, even if it is put in the refrigerator, it should not be more than 4 hours.
8. Boiled eggs, tea eggs and other boiled eggs can be stored in the refrigerator for about 10 days if they are not eaten immediately. However, if the shell has broken, it can only be stored for about 4 days even in the refrigerator in summer, and it can only be stored for about 2 days at room temperature.
Preservation technology
Coating preservation method
1. Principle The coating agent is coated on the surface of eggshell, blocking pores, preventing microorganisms from entering, inhibiting the activity of enzymes, reducing the evaporation of water in eggs, and achieving the purpose of keeping fresh and reducing dry consumption. Commonly used are medical non-toxic liquid paraffin (or solid paraffin), polyvinyl alcohol solution and water glass solution.
2. Method
① Liquid paraffin method. Domestic Shanxi Commercial Institute uses liquid paraffin to coat eggs. After storage for 6 months (April -65438+ 10), the average good egg rate was over 93%, and the average dry consumption rate was about 3%. However, eggs stored for 50 days under the same conditions (without any treatment) are all seriously deteriorated and treated as waste products. After being coated with commercial eggs, they are stored in a refrigerated room at normal temperature (Datong area, the highest temperature does not exceed 27℃ on average). After storage for half a year, the average good egg rate is about 97%, and the dry consumption rate is 0.9 ~ 2.5%. The control eggs were 26 ~ 69.5% and 65438 04.8% respectively. In addition, similar experiments have been carried out in Beijing, Anhui and other places, and similar results have been achieved. The disadvantage of this kind of coating is that the surface of the eggshell has an unpleasant oily or greasy feeling after coating, and liquid paraffin will penetrate into the egg, which will make the substances in the egg have an odor, so some countries (such as Japan) prohibit this kind of coating.
② polyvinyl alcohol (PVA). It is reported that after three months of storage (28 ~ 33℃, humidity 60 ~ 65%), the yield of eggs is 88%. Some scholars suggest that 5% PVA coating is better.
③ Water glass solution. Sodium silicate solution is usually a white, viscous, transparent, water-soluble, non-toxic and tasteless liquid. The concentration of sodium silicate solution used for coating is 3, and Baume degree is 5, which is called Baume degree. After the sodium silicate solution is prepared, the fresh eggs that have passed the preliminary inspection, washed and dried are gently put into the tank, soaked for several minutes, taken out and dried, and put into storage. This method can generally be stored for 4 ~ 5 months. In addition to the above-mentioned common methods, there are mixed coatings composed of vinylidene chloride, mineral oil, linear fatty acid triglyceride, oil, water-soluble polymer, emulsifier and oil, which have achieved good results.