Rapid phase-compositional assessment of lipid-based food products by time domain NMR.

In food science and technology, assessment of phase-compositional behaviour of lipids is critical for understanding many product properties and for effective process control. Time Domain NMR is a rapid and easy-to-handle technique, and is already well appreciated as a tool for phase-compositional assessment in foods. The phase-compositional detail that can be obtained with the established methodology is limited, however. In this work, we set out to obtain more phase-compositional details of lipids as currently feasible with the already established 'classical' NMR methods. We deployed a combined FID-CPMG experiment, and analyzed the Transversal Relaxation Decays by Deconvolution (TRDD) with semi-empirical mathematical functions for solid, semi-solid and liquid components. Within the solid component, different lipid crystal polymorphs can be discerned in a quantitative manner, i.e. alpha, beta and beta'. The TRDD method was validated against established NMR SFC methods, in terms of accuracy ('trueness') and precision. The solid fat content (SFC) of a large collection of fat blends was measured by the commonly employed NMR Direct and Indirect SFC methods and a good correlation with the results of the TRDD was observed, thereby demonstrating accuracy. Furthermore, TRDD was found to be equally precise as the established NMR SFC methods.

MRI of hip prostheses using single-point methods: in vitro studies towards the artifact-free imaging of individuals with metal implants.

Use of magnetic resonance imaging (MRI) in individuals with orthopedic implants is limited because of the large distortions caused by metallic components. As a possible solution for this problem, we suggest the use of single-point imaging (SPI) methods, which are immune to the susceptibility artifacts observed with conventional MRI methods. A further advantage of SPI, based on the fact that signal encoding is achieved in ultra-short times (as short as tens of microseconds), is that they enable the direct visualization of the polymeric elements of the implants, allowing the detection of possible implant failures. We present in vitro SPI images of polymeric sockets of two hip prostheses together with artifact-free images of gelatin phantoms containing their respective metallic stems. These data underscore the great potential of the SPI technique for obtaining artifact-free images of individuals with large metal implants.

Measurement of Oil Droplet Size Distributions in Food Oil/Water Emulsions by Time Domain Pulsed Field Gradient NMR.

A new method for measuring oil droplet size distributions by means of a benchtop pulsed field gradient NMR spectrometer operating in the time domain is presented. The continuous water phase is successfully suppressed by gradient pulses in order to measure the dispersed oil phase. Simulations show that for most common oil/water food emulsions the influence of droplet diffusion is negligible due to a rather large droplet size or a high viscosity of the continuous water phase. The merits of the NMR method relative to other methods are discussed in terms of sample preparation, sensitivity to cluster phenomena, and matrix effects. Preliminary results of a short validation study show a good correlation with conventional reference techniques. Copyright 2001 Academic Press.