Thursday, September 12, 2019

The shape of your tea cup and the flavors of your tea

Another excerpt from my upcoming book "Tea: a Nerd's Eye View:"

Tea is served in glasses, bowls, and cups that come in a multitude of shapes and sizes, made from an amazing array of materials. 
The effects of these different containers has not, to my knowledge, been explored in a systematic and scientific way, where (for example) shape is matched to the qualities of a tea. 
However, there is a growing body of evidence that the shape of a glass influences the aroma  of wine as you drink it. A tulip shape seems to do best for all types of wine. *

The tulip shape allows more aroma volatiles to escape from the surface of the wine; then it concentrates them at the opening at the top of the glass. Thus for wine, one of the important parameters for aroma is the ratio of the opening of the glass (top arrow) to the maximum diameter of the glass (bottom arrow). I was interested to note that the sulfur dioxide diminishes as the ratio goes down, suggesting that this gas is less likely to escape the more tulip-like glass.
A similar result was found for coffee: aromas were more intense when the coffee was served in a cup with a tulip shape, and sweeter when sipped from a cup with a wide opening. Whether these results were the consequence of expectations is open to question—in an online survey of coffee cup shape, respondents maintained that mugs with a narrow opening would be more aromatic, while short mugs with a wide opening would be sweeter.**
Nevertheless, ceramicist Peter Ting has offered a set of three porcelain cups, designed to bring out dfferent aspects of a tea: a “fragrance” cup, a straight sided cup, and a cup with a slightly flared lip.*** 
Towards the end of an extensive podcast on teaware, Kevin Gascoyne shared a tasting experience with host Ken Cohen, sipping a Bai Ruo Xiang Rock Tea from Wuyi from each of Peter Ting’s cups.****
The following table gives the results:

Fragrance cup
Straight-sided cup
Flared lip cup
First sips,
hot tea
Most aromatic, full, complex
Lighter, less flavorful compared to fragrance cup
Less complexity than with fragrance cup, but more “minerality.”
Cooled down
More fruity and “darker” than at first
More complex than first sip, notable minerality

Ting’s fragrance cup is tulip-shaped with a slight flare at the top—the same principle applies here as it does with the tulip-shaped wine glass: aroma volatiles accumulate in the headspace of the cup and then funnels them to your nose and mouth. This cup was designed especially to take advantage of the aromatics in oolongs—this Rock Tea benefitted from this cup.
The straight-sided cup didn’t do justice to the tea. Ting and colleagues found that a straight-sided cup was best for black teas. Black teas, and especially teas made from assamica leaves, tend to be brisk, which is another way of saying that they activate both TRPA1 and TRPV1 receptors on the trigeminal nerve. The straight-sided cup delivers the tea further back in the mouth, where there are more of these receptors, especially TRPV1, so you can expect greater briskness. 
The Wu Yi Rock Tea served by Kevin Gascoyne in this trial lacks many of the TRPV1 activating chemicals, so the “brisk” effect is absent, while the shape of the cup allows the aromatic compounds to escape before you sip, rendering the tea less flavorful. 
As the tea cools down in the cup, however, the warm cool/cold reeptors of the trigeminal nerve are less inhibited by the hot temperature of the tea. The fruity compounds that activate TRPV3, the warm receptor, and TRPM8, the cool receptor, are no longer suppressed, so these flavors can be appreciated—remember, trigeminal activation serves as a volume dial, and trigeminal receptors usually inhibit each other. The one exception: under certain conditions, TRPV! and TRPA1 can mutually enhance, giving the brisk sensation.
Finally, the cup with the slightly flared lip was designed for green tea. The slight flare delivers a wider flood of tea into the mouth, activating more taste buds in the front and sides of the tongue, and fewer in the back. There are proportionally more bitter receptors in the back of the tongue than in the front: this delivery gives the sweeter elements of a green tea a better chance to dampen the  bitterness.  

It’s interesting to note that the flared lip cup yielded a greater sensation of minerality from the Rock Tea. This sensation probably comes from activation of the trigeminal receptor TRPA1. When less fragrance from the tea reaches the nose as you sip, the trigeminal effects in the mouth and throat can become more prominent. As the tea cools down, the ability of TRPA1 to respond increases (it's the cold receptor), so sensations of minerality increase.

All in all, the shape of your cup matters!

Francesca Venturi, Gianpaolo Andrich, Chiara Sanmartin, Isabella Taglieri, Giancarlo Scalabrelli, Giuseppe Ferroni & Angela Zinnai (2016) Glass and wine: a good example of the deep relationship between drinkware and beverage, Journal of Wine Research, 27:2, 153-171, DOI: 10.1080/09571264.2016.1160879 
** George Van Doorn, Andy Woods, Carmel A. Levitan, Xiaoang Wan, Carlos Velasco, Cesar Bernal-Torres, Charles Spence,Does the shape of a cup influence coffee taste expectations? A cross-cultural, online study. Food Quality and Preference, Volume 56, Part A, 2017, Pages 201-211.
*** You can find more about these cups , including pictures, at 

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