Taste of green tea

23 July 2014. NUS scientists have identified the key taste compounds responsible for the taste of unsweetened ready-to-drink (RTD) green tea.

Although the taste profile of black tea has previously been well studied and characterised, that of green tea is much less well understood. A team of researchers led by Professor ZHOU Weibiao (Director, Food Science and Technology Programme) from the Department of Chemistry in NUS and Dr LOW Mei Yin (Flavour Science, Givaudan Singapore Pte Ltd) have now identified the key taste compounds responsible for the bitter and umami tastes and the astringent sensation which are characteristic of unsweetened, RTD green tea beverages. They achieved this through a series of taste reconstruction and omission experiments and analysis. This was published in Food Chemistry. The research was conducted by PhD student Mr YU Peigen and Final Year Honours student Ms Angelin YEO.

First liquid chromatography and taste reconstruction experiments were used to identify a list of potential significant taste compounds. Then taste omission experiments were conducted to investigate taste contribution and significance of individual compounds by removing individual or a group of taste compounds. The half-tongue test (see Figure) was used to simultaneously evaluate and compare different samples in these reconstruction and omission experiments.

The sensory evaluation experiments revealed that the astringent- and bitter-tasting compound (‒)-epigallocatechin gallate, which is the major catechin found in green tea and known also for its various health benefits; the well-known bitter-tasting compound caffeine; and the umami-tasting glutamic acid, an amino acid responsible for the savouriness and broth-like quality of many food products, were the three most important contributors to the taste of RTD green tea.

As a result, regression models could now be developed to predict the intensities of the bitter taste and astringent sensation in RTD green teas from chemical composition data. “This would provide an objective analysis to complement the judgments of professional tea tasters and expert sensory panels,” says Zhou, “to significantly shorten the time for development of higher quality tea beverages.”

Image shows the half-tongue test technique. [Picture credit: YEO ASL]

Reference

Yu P, Yeo ASL, Low MY, Zhou WB. “Identifying key non-volatile compounds in ready-to-drink green tea and their impact on taste profile.” Food Chemistry. 155 (2014) 9.