Solid fat content determination of dispersed lipids by time-domain NMR

Abstract

Time domain nuclear magnetic resonance (TD-NMR) was used to determine the solid fat content (SFC) of dispersions stabilized by a high molecular weight hydrocolloid (gum arabic, GA) containing a high melting lipid (tristearin, SSS). Since the lipid was molten prior to homogenization for the preparation of the dispersion it recrystallizes during cooling and storage. It is known that the recrystallization in a disperse system differs from bulk lipids and TD-NMR could be a helpful tool to investigate the phenomenon. SFC measurement by TD-NMR is well established and widely used in food science for oils, spreads and seeds. In the case of dispersions, however, the situation is more demanding due to the quasi-continuous phase. A suitable TD-NMR method has to account for that and can be realized when combining longitudinal and transverse relaxation properties to separate the signal contribution of the quasi-continuous phase and the solid lipid and liquid lipid dispersed phase. Signal from water and emulsifier was eliminated by magnetization inversion with an initial 180° pulse and a subsequent dedicated inversion delay. The emulsifier showed a longitudinal relaxation similar to the aqueous phase. With a carefully chosen inversion delay, both signal contributions of water and emulsifier could be suppressed, and a quantitative determination of the SFC was possible via dedicated data processing.

Practical applications: The method can be applied in characterization, stability tests and quality control of complex food emulsions and solid lipid particles, which are recently under development as drug carrier systems.

http://ift.tt/2DGGvW4