Polymorphism in Milk Fat Shown by X-ray Diffraction and Infrared Spectroscopy

The occurrence of three polymorphic modifications, alpha, beta-prime, and beta was studied by X-ray diffraction and infrared spectroscopic methods. Excellent agreemerit between the two methods was obtained. Slow cooling of milk fat resulted in formation of the beta-prime and beta modifications. Rapid cooling of milk fat resulted in formation of the alpha form which, upon holding of the sample at 5 C, underwent transformation to the beta-prime and beta forms. The high melting fraction (HIMF) of milk fat obtained by crystallization from acetone existed in the beta form. Slow cooling of the melted I-IMF produced the beta-prime form, rapid cooling the alpha form. X-ray diffraction patterns obtained with milk fat solidified at room temperature were diffuse. Resolution was greatly improved by removal of the liquid portion of the fat by pressure filtration.