APPLICATION OF C-13 NMR-SPECTROSCOPY FOR DETECTION AND QUANTITATIVE-DETERMINATION OF AMINO-ACIDS IN WINE AND FRUIT JUICES

With the help of13C-NMR spectroscopy, the amino acids in wine (wine extract), fruit juices and juice concentrates can be identified and quantified without sample preparation and prior separation in a structure-specific way. Neither the signals of carboxylic groups nor those of carbons bonded to nitrogen are used for the quantitative determination. Comparison of the results gained by the13C-NMR method to the results of the normal analysis with an amino acid analyser shows good accord. Only for some amino acids which form cyclic acid amides (glutamic acid, 4-amino butyric acid) or which have peptide or glycosidic bonds are deviations between the methods observed. In orange juice concentrates and juices, N,N-dimethylprolin (in orange juices 200-740 mg/L) was identified. This compound was not previously known in juices. © 1991 Springer-Verlag.