STUDY OF THE POLYMORPHISM OF SATURATED MONOACID TRIGLYCERIDES .2. POLYMORPHIC BEHAVIOR OF A 50/50 MIXTURE OF TRIPALMITIN AND TRISTEARIN

The polymorphic behaviour of a 50/50 blend of tripalmitin and tristearin has been investigated in detail using differential scanning calorimetry and X-ray diffraction. The blend is characterized by a greater tendency to beta'-crystallization as compared to the pure triglycerides. Tripalmitin and tristearin, when mixed in a 1 : 1 ratio, are miscible in both the alpha-form and the beta'-form. In the beta-form, however, demixing occurs, resulting in a 2-phase solid state. The characteristics of the alpha-form are considerably affected by the crystallization conditions, due to the formation of concentration gradients during crystallization. The beta'-form can be obtained from the melt aswell as via recrystallization of the alpha-form, and is characterized by a much higher stability as compared to the pure triglycerides. The X-ray diffraction data of the beta'-form of the blend reveal a beta'1-crystal structure. The beta'-form of the pure triglycerides, however, is characterized by a beta'2-crystal structure. On the basis of the present data, however, no clear structural distinction can be made between beta'2 and beta'1.