Nuclear Magnetic Resonance in the Analysis of Foodstuffs and Plant Materials

Nuclear magnetic resonance (NMR) is an experimental technique based on the interaction between an applied magnetic field and nuclear magnetic moments in a sample. NMR provides information on material composition, molecular structure, physical structure, physical properties and dynamics of phase changes. NMR is a noncontacting and noninvasive measurement. NMR has been used for the routine analysis of foodstuffs and plant materials. NMR is used in the analysis of foods to detect moisture content, solid/liquid ratio in fats, adulteration of juices and characterization of texture. Applications of NMR to plant materials include observation and characterization of metabolites and ions, determination of pH and following changes of these over time. NMR is also used to determine structures of natural products isolated from plants. Magnetic resonance imaging (MRI) is used in both foodstuffs and plant materials to study morphology and also water transport, diffusion and variations of these under different conditions. The response of NMR is linear from the detection limits of approximately 10 ppb to 100%. The accuracy of the technique depends upon the signal-to-noise ratio (S/N), which is a function of the sample size, applied magnetic field strength, the radiofrequency (RF) coil, the spectrometer hardware and experimental parameters. Typical accuracy is 0.5% for composition and 1–5% for viscosity.