Identification of Amino Acids in Wines by One- and Two-Dimensional Nuclear Magnetic Resonance Spectroscopy

Abstract

Amino acids are minor compounds in wines, but they have a profound influence on wine quality, and amino acids composition can be used to differentiate wines according to the vine variety, geographical origin, and year of production. The NMR signals of amino acids in NMR spectra are overlapped by the signals of other compounds present and especially by the signals of dominant compounds such as water, ethanol, and glycerol. In this work we used 1D ¹H and ¹³C, 2D homonuclear COSY, TOCSY, and 2D heteronuclear HSQC and HMQC pulse sequences, also with an incorporated WET pulse sequence element that allows the simultaneous suppression of several frequencies. Complete ¹H and ¹³C NMR assignments for 17 amino acids commonly present in wine and of γ-aminobutyric acid at pH 3 have been achieved in wine sample of Sauvignon from the Coastal wine-growing region of Slovenia, vintage 1994. Keywords: NMR; wine analysis; amino acids; WET suppression