Why do fats have a melting range?

Answer

Dear Michael,

Fats and oils are, in a difficult word, triglycerides. This means that they consist of glycerol with three fatty acids attached to it. The melting point of a triglyceride depends on the type of fatty acid (saturated or unsaturated) and on the position they occupy on the triglyceride.

Since fats and oils usually consist of mixtures of triglycerides (eg because they have different fatty acids), and each of those triglycerides has its own melting point, you naturally get a wide melting range, where the triglycerides melt one after the other, each at its own melting temperature .
Moreover, in such a mixture they also influence each other’s melting point, making it a kind of continuous trajectory.

Cocoa butter (and therefore chocolate) is an important exception to this. Cocoa butter consists almost exclusively of 3 fatty acids (palmitic acid, stearic acid and oleic acid) and these are very evenly distributed over glycerol, so that you can approximately say that it has only 1 melting point (or at least a very narrow melting range). You also notice this with chocolate: below 30°C chocolate is still solid, above 35°C it becomes quite liquid.

Best regards,

Johan Claes