An egg is composed of three layers: the yolk, the egg white, and the shell.
The yolk coagulates at a temperature of 68°C—71°C, while the egg white coagulates at a lower temperature of 62°C—64°C. When boiling an egg with too high heat, the egg white, which has a lower coagulation temperature, will rapidly solidify and harden on the outside. This prevents heat from continuing to transfer to the yolk, affecting the coagulation of the yolk, which has a higher coagulation temperature. This results in a boiled egg with a cooked white and an undercooked yolk. If boiled for too long, the proteins will denature excessively, making the egg very hard, which is not only unpleasant to eat but also affects digestion and absorption.
Therefore, boiling eggs requires the right method. First, place the eggs in cold water and then heat slowly. Once the water comes to a boil, turn off the heat after about two minutes, let the eggs sit in the hot water for five to six minutes, then remove them and quickly rinse them with cold water before they are ready to eat.