Whether hard-boiled or as a fried egg like here: eggs are part of Easter. With the help of a special X-ray technique, researchers have made visible what happens when the egg white solidifies due to heat
Eggs are one of the most diverse foods: In their raw state they are liquid and their actually separate components – the egg yolk and protein – can be mixed together to create an emulsion. In addition, fried eggs take on a foam-like consistency and when cooked they can be comparatively firm.
Interesting: When an egg is heated up from a temperature of around 80 degrees Celsius, the normally clear protein becomes solid and opaque, as can be seen in our photo. Responsible for this are the proteins in the egg white, which form a network structure due to the heat. How exactly the proteins arrange themselves when heated is not visible to the naked eye.
In order to be able to examine this process more closely, researchers led by Nafasia Begam from the University of Tübingen subjected the protein isolated from chicken eggs to a special X-ray examination. To do this, they filled the protein from chicken eggs into a quartz tube with a diameter of 1.5 millimeters and placed it in the beam of the X-ray light source PETRA III at the German Electron Synchrotron (DESY) in Hamburg.
“The protein was heated in a controlled manner while we analyzed it with X-ray light,” reports co-author Fabian Westermeier from DESY. With what is known as X-ray photon correlation spectroscopy (XPCS), the team was able to follow the structural changes in the protein proteins when they are heated.
In the first three minutes or less, the scientists observed that the proteins unfolded and the protein network grew exponentially. After about five minutes, the network reached a plateau on which almost no further protein links formed. After about a quarter of an hour, the cross-linking of the protein proteins was complete. The proteins were lined up tightly together at intervals of less than a micrometer – the tight-knit, for us opaque protein network of the cooked egg was created.