Identification of coumarin-enriched Japanese green teas and their particular flavor using electronic nose

Abstract

Conventionally, tea flavor is analyzed through the use of a combination of gas chromatography–mass spectrometry and human taste panel. These methods present time-consuming or inaccurate factor. In this work, a rapid, accurate and nondestructive approach was put forward to identify coumarin-enriched Japanese green teas and evaluate their particular flavor using electronic nose (E-nose) technique. The multivariable analyses including principal component analysis and cluster analysis were applied to distinguish the tea samples and evaluate the particular (coumarin-like) flavor of coumarin-enriched tea under different infusion conditions. A correct classification was achieved for the seven tea samples with different content of coumarin. The E-nose successfully characterized the drying temperature-dependently trend of coumarin content during the manufacture process of coumarin-enriched green tea. It also revealed that the comparatively low-infusion temperature and long-infusion time were favorable for the emission of coumarin-like flavor of the tea infusion. In addition, a comparatively newly developed “absolute value expression” (AVE) method was employed to divide the tea flavors into quality and express them numerically. Using AVE, the role of coumarin in the total flavor of coumarin-enriched green tea was elucidated. These results suggest that E-nose could be employed to identify the green teas with particular flavor and evaluate the tea flavor.