A boiled egg can be distinguished from a raw egg without breaking the shell by spinning it. A hard-boiled egg's contents are solid due to the denaturation of the protein, allowing it to spin freely, while viscous dissipation in the liquid contents of a raw egg causes it to stop spinning within approximately three rotations.
Boiled eggs that are difficult to peel are usually too fresh. Fresh eggs have a lower pH, and this does not allow the shell to separate easily from the underlying albumen. When put into vinegar the shell will disintegrate slowly.
Cholesterol and Fat More than half the calories found in eggs come from the fat in the yolk; a 100 gram chicken egg contains approximately 10 grams of fat. People on a low-cholesterol diet may need to reduce egg consumption, although most of the fat in egg is unsaturated fat and may not be harmful. The egg white consists primarily of water (87%) and protein (13%) and contains no cholesterol and little, if any, fat.
A common misconception about eggs in diets is that they contain high levels of cholesterol which is bad for your health. However, eggs contain high levels of HDL (good cholesterol) which actually assists in lowering LDL (bad cholesterol) in the blood.
There is debate over whether egg yolk presents a health risk. Research suggests consuming eggs increases both 'good' and total cholesterol levels, though moderate consumption of eggs, up to two per day, does not appear to increase heart disease risk in healthy individuals. A 2007 study of nearly 10,000 adults demonstrated no correlation between egg consumption and cardiovascular disease or strokes except in the sub-population of diabetic patients which presented an increased risk of coronary heart disease.