Effect of Static Magnetic Field Processing on Crystallization Behavior of Triacylglycerols

The influence of static magnetic field on crystallization of triacylglycerols (TAGs) was investigated. Melted TAGs were solidified under static magnetic field of 5 T with a superconductive magnet system. Polymorphic behavior of TAGs was examined by temperature modulated differential scanning calorimetry (TMDSC) and X-ray diffraction (XRD). In TMDSC experiment, saturated mono-acid TAGs (PPP and SSS) had no change in crystallization behavior under static magnetic field. Static magnetic field processing suppressed the crystallization of α form of SOS, PPO and POS. Furthermore, it suppressed the crystallization of sub-α form, α form, and β ′ form of POP. In case of SSO, the crystallization of α form and β ′ form was suppressed. On the other hand, in the XRD experiment the crystallization of α form in PPP and POP was suppressed by static magnetic field processing. PPO had no change in crystallization behavior under the static magnetic field. However, fluctuation in the ratio of the XRD peak area (wide angle region/small angle region) of α form was increased. This change suggested that the phase transition from α to β ′ form had occurred. From these results, the following can be considered as the influences of static magnetic field on crystallization of TAGs: (i) the effect of static magnetic field on crystallization of saturated mono-acid TAGs depended on the fatty acid chain length which constitutes TAG (PPP and SSS), (ii) the shorter the acyl chains of TAGs, the more sensitive to static magnetic field it was in saturated-unsaturated mixed-acid TAGs (PPO and SSO), and (iii) symmetrical type TAGs (POP and SOS) were more sensitive to static magnetic field rather than asymmetrical type of TAG (POS). It is speculated that the effect of a magnetic field on polymorphism of TAGs is due to the magnetic field gradient in a magnet and the molecular orientation caused by magnetic anisotropy of a TAG molecule. Much work is needed to clarify the mechanism of the polymorphic crystallization under static magnetic field.