Pressure-induced phase transitions in triacylglycerides.
The melting point of triacylglycerides (TAGs) under atmospheric pressure depends on both the fatty acid composition and crystalline structure of the polymorphic state, which are influenced by the temperature treatment history of the TAG. In this contribution, the additional effect of high hydrostatic pressure is described. Samples were placed in a temperature-controlled cell and pressurized up to 450 MPa. The phase transition was investigated either by perpendicular light scattering and transmission or with a polarized-light microscope. The high-pressure polarized-light microscope allows a precise determination of the melting point. The investigated TAGs showed a significant nonlinear increase of the melting point with pressure. Light scattering and transmission were used to observe the phase change in the high-pressure cell. Similar to supercooling in temperature-induced phase transition, we found a dramatic increase of the delay time in our pressure-induced solidification. Even the dependency of this induction time on the control parameter pressure was similar to that in temperature-driven crystallization. We propose that different crystalline structures may be obtained by superpressuring instead of supercooling.
Ferstl
Peter
P
Technische Universität München, Center of Life and Food Sciences Weihenstephan, Freising, Germany. ferstl@wzw.tum.de
Gillig
Sebastian
S
Kaufmann
Christoph
C
Dürr
Christoph
C
Eder
Cornelia
C
Wierschem
Andreas
A
Russ
Winfried
W
D003460:Crystallization; D005227:Fatty Acids / Q000032:analysis; D005524:Food Technology / Q000295:instrumentation; D006874:Hydrostatic Pressure; D008859:Microscopy, Polarization; D044367:Phase Transition; D014280:Triglycerides / Q000737:chemistry*; D014304:Triolein / Q000737:chemistry
D005227:Fatty Acids; D014280:Triglycerides; D014304:Triolein; C004565:trilaurin