Eggheads get a very hard-boiled answer

QUESTION What is the science behind eggs turning hard when they are boiled?

THIS process, unlike other liquids which vaporise, is through denaturation — the breaking of a protein structure by the application of extreme conditions.

Proteins are created by connecting amino acids end to end, then chemical interactions and bonds within the chain cause the proteins to fold into knot-like formations. Each has a unique 3D structure.

Food proteins lose structural shape when an external stressor is applied as the enzymes won’t work if conditions such as the temperature aren’t right.

Egg yolk is largely a protein called albumin and in cooked egg white, the albumin’s folded chain of amino acids has been shaken apart and entangled with others. The change from translucent to opaque is due to coagulation — the bonding of proteins into a solid mass. When proteins denature the chains become more likely to bond and form a solid network. Water gets forced out from between the chains and a stronger, denser association is formed.

Coagulation explains why it is possible to cook soft or hardboiled eggs as the process can be stopped at any time. However, if an egg is cooked for too long the proteins cannot keep water molecules, giving the egg a rubbery texture.

If heat is applied for even longer — over-cooking your egg — the proteins release sulphur atoms which recombine to form a green circle around the yolk. Emilie Lamplough, Trowbridge, Wiltshire.

QUESTION Other than Nancy Richey in the Sixties, has any top female tennis player worn shorts rather than a skirt or a dress?

FURTHER to the earlier answer, we were once at Wimbledon on men’s finals day, and saw Martina Navratilova in a ladies’ doubles match. Of the four ladies on court, she was the only one wearing shorts.

She also wore very dark underwear. This despite a male player being asked to change into white underwear earlier on in the tournament. Maureen and Barry Walker,

Cheadle, Cheshire.