In order to understand I he role of fat in food systems detailed knowledge about the arrangement of triglyceride molecules is useful. The triglyceride molecules in a fat can be packed in alternative ways, each crystal form having different melting points. This phenomenon is called polymorphism.
Based mainly on X-ray studies (single-crystal, powder diffraction , scattering) and Raman spectroscopy the structure of the different polymorphic forms, a, sub-a, P'2. P't and~. are explained. The emphasis is on work done in the author's laboratory.
There is a close relationship between the polymorphic forms which is persistent also in the liquid state - the molecules are arranged two and two in a bilayer. The differences between the polymorphic forms are due to: (i) the hydrocarbon chain packing, (ii) the tilt of the chains versus the methyl end group plane, and (iii) differences in the methyl end group region.
From a technical point of view the polymorphic transitions of fats is of the highest importance. This paper describes a mechanism behind the B --> B transition - the chain mobility in the methyl end group region causes this transition.
"Polymorphism of Triglycerides a Crystallographic Review,"
Food Structure: Vol. 9
, Article 5.
Available at: http://digitalcommons.usu.edu/foodmicrostructure/vol9/iss1/5