title: Application of pulsed field gradient NMR techniques for investigating binding of flavor compounds to macromolecules.
abstract: Two diffusion-based NMR techniques are presented and used to investigate the binding of selected flavor compounds to macromolecules. A pulsed field gradient NMR (PFG-NMR) method was applied to measure the apparent diffusion coefficients of four alkanone compounds as they associated with bovine serum albumin (BSA). The change in the apparent diffusion coefficient as a function of the BSA/alkanone ratio was fitted to yield binding constants (K(a)()) and binding stoichiometry (n) for each alkanone. The results showed that the apparent diffusion coefficients of alkanones increased with a decrease in the BSA/alkanone ratios, and the measured values of K(a)() and n were comparable with those obtained with other methods and depended on the alkanone structure. A diffusion-based nuclear Overhauser effect (called diffusion NOE pumping) method was also applied to screen mixtures of flavor compounds and identify those that have a binding affinity to complex macromolecules. Using this technique benzaldehyde and vanillin were observed to bind with bovine serum albumin, whereas 2-phenylethanol was identified as a nonbinding or weakly binding ligand with BSA. The diffusion NOE pumping method was also applied to a hydro alcoholic solution of cacao bean tannin extracts to which a mixture of ethylbenzoate, benzaldehyde, and 2-phenylethanol was added. The diffusion NOE pumping technique clearly indicated that ethylbenzoate had a stronger binding affinity to the polymeric (-)-epicatechin units of the cacao bean tannin extracts than the other two flavor compounds. The results successfully demonstrate the potential applications of diffusion-based NMR techniques for studying flavors and nonvolatile food matrix interactions.
authors.affiliation: Department of Viticulture and Enology, and NMR Instrumentation Facility, University of California, Davis, California 95616-8749, USA.
authors.forename: Da-Mi
authors.initials: DM
authors.lastname: Jung
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: De Ropp
authors.forename: Susan E
authors.initials: SE
authors.lastname: Ebeler
mesh_terms: D001547:Benzaldehydes / Q000378:metabolism; D004058:Diffusion; D005421:Flavoring Agents / Q000378:metabolism*; D005502:Food; D047348:Hydrolyzable Tannins / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008433:Mathematics; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D013649:Taste
chemical_list: D001547:Benzaldehydes; D005421:Flavoring Agents; D047348:Hydrolyzable Tannins; D012710:Serum Albumin, Bovine; C100058:vanillin; C032175:benzaldehyde