Boil eggs and simmer for 3 minutes just fine. Eggs should be cooked in a cold water pot, warmed up slowly, boiled for 3 minutes, then stopped for 5 minutes. The boiled egg is tender and the egg yolk is solidified and not old. The degree of protein denaturation is the best and it is also the most easily digested. When the egg is boiled for more than 10 minutes, not only does the taste become old, but also the loss of vitamins makes the protein difficult to digest.