A graphic demonstration of the differences among green, oolong, and black teas.

Here’s a graph from the paper by Li-Fei Wang and colleagues that I mentioned in yesterday’s post.* It characterizes the aroma chemicals in tea through solid-phase microextraction–gas chromatograph (SPME–GC).  The top graph comes from a green tea (Ouksu tama-ryokucha, which is both steamed and roasted), the middle graph from a Dong-Ding (Tung-Ting) oolong, and the bottom graph from an English breakfast  (black) tea. The height of the peaks indicates the abundance of each chemical in the extract.

SPME–GC separates the chemicals that have a “green” quality—in other words chemicals that activate the cool/cold receptors—from the chemicals that activate the warm and hot receptors. I drew the green line to show the border between the two types of chemicals, primarily cool/cold on the left, and primarily warm/hot on the right.

As you can see, the green tea’s aroma chemicals (top graph) lie predominantly to the left of the line, which corresponds with the fact that green tea pairs well with foods that have a cool/cold aroma such as lemon, mint, and ginger.

As you go to the next graph, from Dong-Ding oolong, you’ll notice a marked difference from the green tea graph, with high peaks to the right as well as to the left. Note too, that there are far more high peaks altogether, consistent with the complexity of oolong flavor. Oolongs can be paired with both cool/cold and warm/hot aroma foods, though pairing is best with foods such as rosemary and strawberries that activate the primarily the warm (not hot) receptors. 

Black teas have very little of the green chemicals, and a somewhat lower quantity of the warm/hot aromas than oolong (bottom graph). The net effect is a far less complex flavor than that of the oolong, but the lack of cool/cold aromas means better pairing with foods with aromas that bind to hot receptors, such as raspberries and chocolate.

* Li-Fei Wang, Joo-Yeon Lee, Jin-Oh Chung, Joo-Hyun Baik, Sung So, Seung-Kook Park. Discrimination of teas with different degrees of fermentation by SPME–GC analysis of the characteristic volatile flavour compounds. Food Chemistry. Volume 109, Issue 1, 1 July 2008, pages 196–206.