A soft-boiled or hard-boiled egg is simply part of the perfect breakfast, but alas, the shell cannot be peeled off… One egg comes out of the shell easily, but the other does not at all, so hard-boiled pieces of protein often stick to the shell. How can that be? Was the egg missing a long, cold shower? Or is it a myth that eggs have to be cold quenched to make them easier to peel?
“Yes,” says Thomas Vilgis, a researcher at the Max Planck Institute for Polymer Research in Mainz and an expert in the physics of food. It’s a combination. “It is said again and again that deterring is of little or no use. I can’t really confirm that.” On the contrary: “When the egg from the approximately 90 degree hot water meets 20 degree warm water, the shell, the skin and the albumen contract at different speeds. This difference forms microcracks that make it easier to peel the egg.”
Another decisive factor is the age of the egg: “The sticky skin that sits between the shell and the egg white consists of proteins. These react to changes in the pH value. As a result, the proteins change their ability to bind and the egg can be peeled easily,” according to the researcher. The combination of age and cold quenching is thus crucial to peeling an egg. The researcher gives one more piece of advice: “If you want to really quench an egg, put the egg in cold water that has been cooled to zero degrees using ice cubes or ice packs.”
However, if you want to store hard-boiled eggs for longer, Silke Noll, a nutrition expert from the Bavarian Consumer Advice Center, advises against putting them off. Because the cold water causes cracks to form in the shell, which shortens the shelf life of the ice cream because germs could penetrate. Undamaged hard-boiled eggs can be stored in the refrigerator for up to four weeks.
