Effect of Copper on Fatty Acid Profiles in Non- and Semifermented Teas Analyzed by LC-MS-Based Nontargeted Screening.
Unsaturated fatty acids are well-known precursors of aroma compounds, which are considered important for green tea quality. Due to the known copper-induced oxidation of unsaturated fatty acids and the broad variability of the amount of copper present in tea infusions, this paper investigates the influence of copper, added at a nontoxic concentration (300 μM) to non- and semifermented teas, on the degradation of fatty acids and fatty acid hydroperoxides thereof. The abundance of fatty acids in green and oolong tea was determined by means of a nontargeted approach applying high-resolution MS/MS. As a result, most of the fatty acids in green and oolong tea were already oxidized prior to copper addition. Addition of 300 μM CuSO4 to the oolong tea sample resulted in a decrease of 13-hydroperoxy-9Z,11E-octadecadienoic acid, an important flavor precursor, from 0.12 ± 0.02 to 0.05 ± 0.01 μM (p = 0.035), and other oxidized fatty acids decreased as well. However, copper-induced degradation of oxidized fatty acids was less pronounced in green tea compared to oolong tea, most likely due to the formation of copper complexes with low-molecular-weight compounds as evidenced by electron paramagnetic resonance spectroscopy.
Department of Nutritional and Physiological Chemistry, Faculty of Chemistry, University of Vienna , 1090 Vienna, Austria.
Marc
M
Pignitter
Institute of Animal Nutrition and Functional Plant Compounds, University of Veterinary Medicine Vienna , 1210 Vienna, Austria.
Klaus
K
Stolze
Department of Inorganic Chemistry, University of Vienna , 1090 Vienna, Austria.|Department of Zoology, University of Johannesburg , P.O. Box 524, Auckland Park, 2006 South Africa.
Franz
F
Jirsa
Institute of Pharmacology and Toxicology, University of Veterinary Medicine Vienna , 1210 Vienna, Austria.
Lars
L
Gille
State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University , 530004 Nanning, Guangxi, China.
Bernard A
BA
Goodman
Department of Nutritional and Physiological Chemistry, Faculty of Chemistry, University of Vienna , 1090 Vienna, Austria.
Veronika
V
Somoza
D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003300:Copper / Q000737:chemistry*; D005227:Fatty Acids / Q000737:chemistry*; D005285:Fermentation; D005421:Flavoring Agents / Q000737:chemistry; D010084:Oxidation-Reduction; D053719:Tandem Mass Spectrometry / Q000379:methods; D013662:Tea / Q000737:chemistry*
D005227:Fatty Acids; D005421:Flavoring Agents; D013662:Tea; D003300:Copper
copper; epigallocatechin-3-gallate; fatty acid; nontargeted screening; polyphenol; tea