Surfaces of Beer Studied by Sum-frequency Generation Spectroscopy

Abstract

We investigated the molecular composition of the surface of beer and the orientations of these molecules on the beer surface using sum-frequency generation spectroscopy. By measuring the representative substances contained in beer, it was shown that hop-derived iso-α-acids and isoxanthohumol exist on the beer surface. Furthermore, these hop-derived molecules significantly contribute to the stability of beer foam by forming surface-active species with hydrophobic proteins on the beer surface.