Influence of high pressure on the relative permittivity of oleic acid

Abstract

Oleic acid (OA) is a monounsaturated omega-9 fatty acid which undergoes a first-order phase transition when it is influenced by high pressures. The transition results in a change of molecular structure, which was investigated by means of X-ray techniques [J. Przedmojski and R.M. Siegoczyński, X-ray diffraction investigation of oleic acid under high pressure, Phase Transit. 75 (2002), pp. 373–377]. Despite a significant change in the structure, the permittivity of the acid remains barely influenced during and after the phase transition. A rise in relative permittivity has been observed due to the increasing number of molecules per volume unit within a compression cycle. However, no significant fall in the permittivity has been observed as a result of the transition which occurs in the case of edible oils. This may be caused by a strongly dimerised structure and dipole–dipole interaction in the liquid at ambient pressure.

Keywords:

• oleic acid
• high pressure phase transition
• relative permittivity
• dipole moment

Notes

^†This paper was presented at the 6^th International Conference on High Pressure Bioscience, Biotechnology (HPBB 2010), Freising (Germany), 28 August–1 September 2010.