Frank Oliver, Blumberg Simone, Krümpel Gudrun, Hofmann Thomas
Lehrstuhl für Lebensmittelchemie and Molekulare Sensorik, Technische Universität München, Lise-Meitner-Strasse 34, D-85350 Freising-Weihenstephan, Germany.
J Agric Food Chem. 2008 Oct 22;56(20):9581-5. doi: 10.1021/jf802210a. Epub 2008 Sep 26.
Recent investigations on the bitterness of coffee as well as 5- O-caffeoyl quinic acid roasting mixtures indicated the existence of another, yet unknown, bitter lactone besides the previously identified bitter compounds 5- O-caffeoyl- muco-gamma-quinide, 3- O-caffeoyl-gamma-quinide, 4- O-caffeoyl- muco-gamma-quinide, 5- O-caffeoyl- epi-delta-quinide, and 4- O-caffeoyl-gamma-quinide. In the present study, this orphan bitter lactone was isolated from the reaction products generated by dry heating of 5- O-caffeoylquinic acid model, and its structure was determined as the previously unreported 3- O-caffeoyl- epi-gamma-quinide by means of liquid chromatography-mass spectrometry (LC-MS) and one-/two-dimensional NMR experiments. The occurrence of this bitter lactone, exhibiting a low bitter recognition threshold of 58 micromol/L, in coffee beverages could be confirmed by LC-MS/MS (negative electrospray ionization) operating in the multiple reaction monitoring mode.
最近对咖啡苦味以及5-O-咖啡酰奎尼酸烘焙混合物的研究表明，除了先前鉴定出的苦味化合物5-O-咖啡酰-粘胶-γ-奎尼德、3-O-咖啡酰-γ-奎尼德、4-O-咖啡酰-粘胶-γ-奎尼德、5-O-咖啡酰-表-δ-奎尼德和4-O-咖啡酰-γ-奎尼德之外，还存在另一种未知的苦味内酯。在本研究中，这种未知的苦味内酯是从5-O-咖啡酰奎尼酸模型干热产生的反应产物中分离出来的，并通过液相色谱-质谱联用（LC-MS）和一维/二维核磁共振实验确定其结构为先前未报道的3-O-咖啡酰-表-γ-奎尼德。通过在多反应监测模式下运行的LC-MS/MS（负电喷雾电离）可以证实这种苦味内酯在咖啡饮料中的存在，其苦味识别阈值低至58 μmol/L。
