Food Analysis Using Fast Steady-State Free Precession TD-NMR Relaxometric Methods
The importance of NMR relaxometry in food analysis has been growing at a fast pace in recent years. Most food-related applications rely upon the transverse relaxation time (T2) that can be measured with a single-shot method using the Carr-Purcell-Meiboom-Gill pulse sequence. On the other hand, the longitudinal relaxation time (T1) has been seldom used due to the long measurement time of classical methods (e.g., inversion recovery, saturation recovery, and other pulse sequences). To by-pass the long acquisition time, several single-shot, steady-state methods have been proposed to measure T1, T2, and T1/T2 ratio. This chapter presents and discusses the advantages and disadvantages of rapid, single-shot continuous wave free precession (CWFP) pulse sequences in the measurement of T1 and T2 through single experiments; a single-shot CWFP method to measure T1 in spectrometers with long dead time; a fast method to measure the T1/T2 ratio in grossly inhomogeneous magnetic field (Split 180), and a fast 2D method based on driven-equilibrium Carr-Purcell-Meiboom-Gill (DECPMG) sequences to obtain T1/T2 maps. Examples of application of these sequences for monitoring food quality are also presented.
KeywordsCWFP Low resolution NMR Relaxometry SSFP Time domain NMR
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