Common poultry are: geese domesticated by wild geese, domestic chickens domesticated by original chickens, etc. Poultry not only provides meat and eggs for human beings, but also their feathers and feces have important economic value.

Introduction to poultry and eggs-basic knowledge of eggs

Introduction of poultry and eggs

Poultry introduction

Birds domesticated by human beings for economic or other purposes. Poultry breeding and domestication have a history of thousands of years in China, and many world-famous varieties have been cultivated. For example, among domestic ducks domesticated by wild ducks, Beijing Duck is a good variety, with an annual output of 70 ~ 120 eggs. The Beijing Roast Duck made from it is well-known at home and abroad for its delicacy.

Other common poultry are: geese domesticated by wild geese, domestic chickens domesticated by original chickens, etc. Poultry not only provides meat and eggs for human beings, but also their feathers and feces have important economic value.

Introduction of eggs

Eggs are eggs laid by some land animals, and the embryos are covered with waterproof shells. Birds, reptiles, mammals, platypus and echidna all lay eggs. At a proper temperature, the eggs will hatch in a certain time, and the larvae will break out with the keratin above their mouths. Eggs are rich in nutrition and low in price. They can be made into stewed eggs, tea eggs, cakes and other delicacies, and have been regarded as the best source of nutritional supplements since ancient times. It's also a movie.

Choice of eggs

When buying eggs, please pay more attention to the following items to avoid buying them? Bad guys? ：

If you put an egg in 4% salt water, it is a good egg that will sink immediately.

The bigger the air chamber of an egg, the worse the quality.

Choose washed eggs that have completely removed dirt and bacteria from the eggshell.

If the eggshell is damaged, bacteria may have grown and should not be purchased.

Try to choose eggs marked with CAS quality eggs.

The coarser the shell, the fresher the egg.

It is best not to buy traditional chicken manure, dirt and rice eggs.

Newborn eggs, whose shells are wet and cuticles are not yet dry, are easily invaded by bacteria such as Salmonella and Staphylococcus aureus, so it is best not to buy them immediately.

The rounder an egg is, the bigger its yolk is.

Preserved eggs with high lead and copper content will have more spots on the eggshell surface. After shelling, you can also see that the color of protein is dark green or occasionally black spots, which is not suitable for purchase.

Some preserved eggs made by traditional methods will wrap red soil and straw on the surface of the eggshell, which is actually unsanitary and inconvenient to judge the lead content by appearance, so it is not suitable for purchase.

Storage of eggs

Eggs are rich in protein. If stored improperly, they will soon go bad and rot. Therefore, after the eggs are bought back, in order to eat safely and healthily, it is best to store them in the following ways.

If you buy traditional eggs in bulk, you must wash them thoroughly and dry them before putting them in the refrigerator.

The shelf life of packaged washed eggs sold in supermarkets is about 14 days.

Eggshells are afraid of moisture, so they should not be confined in airtight plastic boxes to avoid being damp and moldy.

When laying eggs, the rounded end should face up and the pointed end should face down.

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.

Generally, fresh eggs with shells can be kept in the refrigerator for about 7 days in summer and about one month in winter.

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.

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 of eggs

Coating preservation method

Principle: Coating film on eggshell surface can block pores, prevent microorganisms from entering, inhibit the activity of enzymes, and reduce the evaporation of water in eggs, so as to achieve the purpose of keeping fresh and reducing dry consumption. At present, medical nontoxic liquid paraffin (or solid paraffin), polyvinyl alcohol solution and water glass solution are widely used.

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, the control eggs (without any treatment) were all seriously deteriorated for 50 days under the same conditions and were 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.

polyvinyl alcohol (PVA)

It is reported that after the eggs were wrapped with PVA for 3 months (temperature: 28 ~ 33℃, humidity: 60 ~ 65%), the rate of good eggs was 88%. Some scholars suggest that 5% PVA coating is better.

Sodium silicate 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.

Nutritional value of eggs and hidden crisis

Eggs are one of the most important foods for human beings. Common eggs include eggs, duck eggs, goose eggs and quail eggs. , with almost the same nutritional composition and structure, of which eggs are the most common. Eggs are composed of eggshells, yolk, protein and egg tendons, which have the following nutritional values.

Eggshell: Eggshell is rich in calcium carbonate, which is very easy to digest and absorb and is the best source of calcium supplement. Under normal circumstances, grinding about 2 grams of eggshells into powder every day can prevent backache, easy fracture or osteoporosis caused by calcium deficiency and bone loss.

Protein: protein contains a kind of protein called albumin, which has the function of scavenging active oxygen, enhancing human immunity and preventing cancer. Moreover, after being decomposed by digestive enzymes, the ovalbumin in protein can produce lysozyme, which can activate macrophages, resist the invasion of foreign germs and improve the immunity of the body.

Egg frenulum: There are two white bands around the yolk, which is the egg frenulum. It 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.

Egg yolk: Egg yolk is rich in nutrients such as protein, fat, calcium, lecithin and iron. Lecithin can promote the elimination of cholesterol in blood vessels and prevent atherosclerosis after being absorbed by gastrointestinal tract. Moreover, after lecithin is digested and absorbed, it can produce choline, which is related to the nerve transmission function of the brain and can promote the ability of learning and memory, thus achieving the effect of preventing Alzheimer's disease. Choline can also prevent the liver from accumulating too much fat, avoid fatty liver and improve liver function. The iron contained in egg yolk has the highest utilization rate and is the most blood-enriching natural food.

So-called? Extremes must be reversed? Although eggs have high nutritional value, it does not mean that the more eggs you eat, the better. Let's take a look at what crises are hidden behind eggs with high nutritional value.

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.

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.

Which parts of poultry can't be eaten?

Chicken, duck, pork, fish and other meats are all essential foods in our daily diet, but some parts of these poultry are prone to health problems, and they are also prone to health problems after eating human bodies. Therefore, these parts of the following poultry must not be eaten.

Rabbit? Smelly gland? The rat gizzard located under the skin on both sides of the back of the external genitalia, the brown rat gizzard next to the rat gizzard and the rectal glands on both sides of the rectum have a very unpleasant smell. If you don't remove them when eating, it will make rabbit meat difficult to swallow.

Livestock? Three glands? Pigs, cows, sheep and other animals have thyroid gland, adrenal gland and pathological lymph gland? Physically harmful organs? .

Sheep? Hanging ribs? : Also known as? White hoof beads? Generally, it is bead-shaped and granular, which is a kind of tissue with lesions in sheep's hoof.

Bird? Sharp wings? What is the scientific name of the tail feather at the top of the ass of birds such as chickens, ducks and geese? Superior vena cava? It's where the lymph glands are concentrated. Because macrophages in lymph glands can devour germs and viruses, even carcinogens can be swallowed, but they cannot be decomposed. Sharp wings? Is it shelter evil people from evil practices? Warehouse? .

Fish? Black? There is a black coating on both sides of the abdominal cavity of fish, which is the most fishy and earthy part, and contains a lot of lipid-like, lysozyme and other substances.