2. At this time, the egg is heart-shaped and has the highest nutritional content, which is most conducive to human absorption. Wash the eggs, put them into the pot with cold water, boil them, time them for 3 or 5 minutes respectively, and take them out after cooling. "3-point egg", the egg white is cooked and soft, and the yolk is just cooked and slightly cooked. "5-point egg", the egg white is cooked and tender, and the yolk is cooked but not hard. Eggs cooked at different times have different digestion time in human body. "3-point egg" is slightly cooked and is the easiest to digest, which takes about 1 hour for 30 minutes; "5 minutes" eggs are half cooked, and the digestion time in the human body is about 2 hours; Eggs boiled for too long take a relatively long time to digest in the human body. The most nutritious is "5-cent egg", which is not only soft and tender, but also beneficial to human nutrition.

3. If the egg is boiled in boiling water for more than 10 minutes, a series of chemical changes will take place inside. The structure of protein becomes more compact, and it is not easy to contact with protein digestive enzymes in gastric juice, so it is more difficult to digest. Protein in eggs contains more methionine. After a long period of heating, it will decompose into sulfide, which will react with the iron in the egg yolk to generate iron sulfide which is not easily absorbed by the human body, resulting in more nutritional losses.