The proportion of amino acids in eggs is closest to the needs of human body


  Poultry egg (including egg, duck egg, goose egg, pigeon egg, quail egg, etc.) is a food with high nutritional value. It contains excellent protein, fat, lipid, minerals and vitamins necessary for human body. The proportion of eggshell, protein and yolk is related to the variety, age, laying season, egg size and feeding method of poultry. Generally, egg protein accounts for 58%, egg yolk 30.5% and eggshell 11.5% (mass ratio).

  It is generally considered that the protein of eggs is the best, the protein digestibility is 98%, and the biological value of whole eggs (the mass of protein converted into human protein per 100 grams of food source protein) is 94. It is 1.3 times of protein in general Cereals, 1.6 times of beans, 1.2 times of fish and meat, and about 1.1 times of milk.

  Due to the complete variety of amino acids in egg protein, and the proportion of various amino acids is close to the needs of human body, the amino acid proportion of egg is often scored as 100 to evaluate the quality of other proteins.

  Egg is an almost perfect amino acid food. In other foods, one or two essential amino acids are usually insufficient or completely lacking. These are called "restricted amino acid" foods (restricted amino acids refer to the amino acids with low ratio between the amount of essential amino acids contained in food and the amount of essential amino acids in protein required by human body. Due to the deficiency of these amino acids, the body's utilization of other essential and non essential amino acids is limited, and eggs are the amino acid food that can provide the best balance among common ingredients.

  The egg protein will solidify after heating. For example, the egg protein solidifying temperature is 62 ~ 64 ℃, the egg yolk solidifying temperature is 68 ~ 71.5 ℃, and the mixed egg liquid is 72 ~ 77 ℃. The freezing point of protein was -0.41 ~ -0.48 ℃. The freezing point of egg yolk is -0.545 ~ -0.617 ℃. Mastering the freezing temperature and freezing point of eggs is of great significance for egg sterilization and fresh egg refrigeration. Due to the different chemical components between egg yolk and protein, the osmotic pressure of egg yolk and protein is different. The salts of potassium, sodium and chlorine plasma in egg yolk are higher than protein, so the osmotic pressure is higher than protein.

  During the storage of eggs, the salts in the egg yolk continue to penetrate into the protein, and the water in the protein also continues to penetrate into the egg yolk. Because the strength and elasticity of the egg yolk membrane gradually decrease, the egg yolk expands. When the egg yolk membrane cannot bear the pressure of the egg yolk, the egg yolk membrane breaks, resulting in scattered yellow. When studying the freshness of eggs, egg yolk index (remove the eggshell, place the complete egg content on the plate, and the ratio of egg yolk height to transverse diameter) is often used to measure the freshness of eggs. The yolk index of fresh eggs is 0.401 ~ 0.442. If it is less than 0.25, the yolk film will rupture. Fresh eggs at higher temperature (above 25 ℃) will cause physiological changes of embryos. The embryonic development of a fertilized egg produces reticular blood filaments, which are called embryonic eggs. According to the degree of development, it can be divided into blood circle egg, white muscle egg and blood circle egg. Unfertilized embryos also had swelling, but there was no vascular phenomenon. This physiological change of eggs often reduces the quality of protein, reduces the pressure resistance, and even deteriorates.

  The protein of egg is sulfur-containing. In the process of protein corruption, various complex reactions such as hydrolysis, decomposition, oxidation and reduction will occur. Sulfur will be transformed into H2S, HS -, S2 - and so on under anoxic conditions. H2S release will produce the so-called "rotten egg smell". These - 2 valent sulfur elements will also combine with Fe2 + originally contained in eggs to produce FES (blue black). When you cook an egg, if you cook it for a long time, the surface color of the egg yolk will become darker. That's why.

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