Oolongs, between green and black

So excited to be presenting at World Tea Expo with Donna Fellman of the World Tea Academy! We'll be showing off the organoleptic properties of oolongs in our Skill Building Workshop. 

To get ready, I've been looking at the most recent work on oolongs, and came across a paper* where the authors not only did an analysis of the chemicals in the aroma of three different oolongs, but also had trained tasters evaluate the teas for roasted, sulfur, sweet, floral, and green/grassy qualities. They then correlated these qualities with the various aroma chemicals they found.

What struck me: that not only were there positive correlations between chemicals and these qualities, but that there were also negative correlations.

What do these negative correlations mean? That certain chemicals inhibit our ability to sense other chemicals. As the authors put it:

"Positive as well as negative correlations suggest that the perception of an aromatic note was influenced not only by the presence of a few compounds whose aroma forms the attribute but also by the presence of other odorants that affect negatively in the perception of such aromatic attribute." 

The results fit perfectly with my own observations concerning hot, warm, cool, and cold receptors. These receptors are mutually inhibitory, so that hot inhibits cool and cold, and vice versa.

With DaHongPao, which is closer to black tea in its processing, roasted aromas (hot receptors) decreased the ability to sense grassy and green aromas (cool/cold receptors) even though green/grassy chemicals were present in the tea. By contrast, with DongDingWulong, which is closer to a green tea, green/grassy aroma chemicals were more abundant than roasted aroma chemicals, so the roasted aroma chemicals were "hidden." 

You'll experience these differences and more in our Skill Building Workshop, so don't forget to sign up for World Tea Expo, June 15-17, 2016, in Las Vegas: http://www.worldteaexpo.com/wte16/Public/enter.aspx.

Here's the spider graph from the article showing the average scores for each of the qualities:

DHP = DahongPao; TGY = TieGuanYin; DD = DongDingWulong.

* JianCai Zhu et al. Comparison of Aroma-Active Volatiles in Oolong Tea Infusions Using GC−Olfactometry, GC−FPD, and GC−MS. J. Agric. Food Chem. 2015, 63, 7499−7510.