The more saturated, the higher the melting point. As would follow, the more unsaturated the fatty acids, the lower the melting point. The solid property of fat is influenced by the presence of crystallized fat. Fat crystals are held together by Van der Waals forces and thus are not terribly strong. They can be rearranged, broken, and reformed.
Polymorphism is the existence of more than one crystal form in a fat.
The forms are alpha, beta-prime, and beta,and range from least stable to most stable, respectively. Crystallization can be modified through the process of interesterification. Interesterification is the process of changing the position of naturally occuring fatty acid radicals on the glyceride backbone to effect different properties. Deterioration of the flavor components in lipids often leads to disaster in food and beverage products because of the noticeable off tastes. Care must be given to build the correct system such that the selected fat or oil remains stable for the maximum length of time.