DETECTION OF FLAVOR SUBSTANCES USING SURFACE-PLASMON RESONANCE WITH LIPID LB MEMBRANES

The technique using the phenomenon called surface plasmon resonance ca n make it possible to detect the change of refractivity (or dielectric constant) of a solution in a thin local region (the typical thickness of the region is about 1 mu m), which is very close to the surface of a thin basal metal plate. Interactions between lipid molecules and fl avor substances were investigated by using the surface plasmon resonan ce. In this study, the effects of various kinds of flavor substances-w hich can be regarded as representative of the five kinds of basic tast es (sweet, salt, sour, savory, and bitter)-on the lipid membranes were examined. The lipid membrane utilized as a receptor for taste substan ces was the LB (Langmuir-Blodgett) multilayered film composed of dihex adecyl phosphate. It was found that almost no flavor substances had an y observable interactions to the lipid membrane system, while quinine hydrochloride, the representative of bitterness, was found to be stron gly adsorbed to the lipid membrane. It was shown by doing measurements for various numbers of layers of the membrane system that the quinine hydrochloride is absorbed not only onto the surface but into the inte rnal region of the lipid layers. It was observed that the sweet substa nce or salty substance suppressed the adsorption of the bitter substan ce. Similar suppression effects can also be found in biological system s. (C) 1997 Scripta Technica, Inc.