Nuclear magnetic resonance screening effect

Analytical methods involving exhaustive extraction of flavor compounds (i.e., liquid/liquid extraction, dynamic headspace) do not take these matrix effects into account. However, new instrumentation and methodologies are yielding improved information on the mechanisms involved in flavor/matrix interactions and the effects on flavor perception. For example, spectroscopic techniques, such as nuclear magnetic resonance (NMR), can provide information on complex formation as a function of chemical environment and have been used to study both intra- and intermolecular interactions in model systems [28,31]. In addition, NMR techniques, initially developed to study ligand binding for biological and pharmaceutical applications, were applied in 2002 to model food systems to screen flavor mixtures and identify those compounds that will bind to macromolecules such as proteins and tannins [32]. Flavor release in the mouth can be simulated with analytical tools such as the retronasal aroma simulator (RAS) developed by Roberts and Acree [33]. These release cells can provide... 

Because of the important link between coordination environment and chemical shift, a brief review of the components of shielding are presented here (99). To a certain extent, circulation of electrons screens a nucleus from an external magnetic field, Bq, so that the effective field felt by the nucleus, is defined in Eq. 3, where ct (the shielding) is a measure of the nuclear screening. The resonant frequency is proportional to the ef-... 

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