Polymorphism of stabilized and nonstabilized tristearin, pure and in the presence of food emulsifiers

The polymorphism of tristearin (SSS) was studied by means of differential scanning calorimetry and powder X-ray diffraction. The influence of 5% in weight of different food emulsifiers-i.e., 1-monostearin, sorbitan tristearate, and sugar monostearate-was also studied. Because polymorphism is sensitive to thermal treatment, two thermal conditionings were applied. According to the dynamic process (melting, quenching, and heating at 5 degrees C/min), SSS showed three polymorphic forms: alpha, beta', and beta(1). The presence of the emulsifiers hindered the beta' --> beta transformation, and a destructured beta(2) form was recorded. According to the stabilization process (stabilization at 57 degrees C for various periods of time), SSS showed two beta' forms: beta(2)' and beta(1)'. Three hours of stabilization were necessary to recover the whole triglyceride under the beta form. The emulsifiers slowed dawn the polymorphic transition rates. Indeed, after six hours of stabilization, mixtures of beta' and beta were observed. Sugar monostearate seemed to have the most powerful effect on the transition kinetics because large amounts of a form were detected.