Asparagus aroma in tea

Just the other day I saw mention that a certain green tea tasted like asparagus. I love asparagus, but I have yet to taste a green tea that reminds me of the vegetable. That observation led me into looking at the nature of the volatiles in asparagus, and here’s what I found:*

The strongest odorants, and perhaps the most numerous, in asparagus are sulfur-containing and nitrogen-containing compounds—these can be detected by the human nose at the level of parts per billion. They will dominate any aroma mixture you can imagine. 

Of these 20 or so compounds in asparagus, the most abundant and dominant is dimethyl sulfide. This compound can be present in tea, where (to me at least) it contributes a “marine/seashore/oceanic” quality. You can find it most abundantly in green and oolong teas, so it would not be surprising that when you encounter it in a green tea, it might give the impression of asparagus. It is notable, however, that the remaining sulfur compounds detected in asparagus, with the exception of dimethyl sulfoxide, are not usually found in tea. The nitrogenous compounds common in asparagus—pyrazines—are also rare in teas. 

What is found in both tea and asparagus are a few volatiles with a decidedly less asparagus-like aroma, for example hexanal, which gives a “green” aroma and has a lingering after-taste; and two of my favorites, benzene ethanol and phenyl acetaldehyde, both of which have the fresh, sweet rose-like aroma that I love in oolongs, and especially white tea. Next time I have asparagus, will have to look for them.

Asparagus cooking, by Seeman, from Morguefile.com

In the olfactory bulb, before we ever are conscious of an aroma, we assemble the signals from volatile chemicals into an “odor object.” As Ulrich and colleagues note: 

“a lot of weaker smell impressions were recognizable in the odor spectrum which are potentially able to contribute by interactions to the whole aroma impression.” 

...in other words to the assembly of a recognizable “odor object.” 

Further, people surely differ in the odor objects they create from a given panoply of possibilities—remember that we don’t all smell the same things in a mixture, and we may not use the same array of volatiles to construct a recognizable odor object. 

So what I myself may experience as simply “seashore” may be just one part of someone else’s “asparagus” aroma.** 

* Ulrich, D., Hoberg, E., Bittner, T. et al. Contribution of volatile compounds to the flavor of cooked asparagus. Eur Food Res Technol (2001) 213: 200. doi:10.1007/s002170100349.

** Incidentally, I’m talking about the smell of cooked asparagus in the plate, not the smell that some people create and some people can smell in urine. These are metabolites of asparagusic acid. These metabolites do include dimethyl sulfide and also the garlic-like dimethyl disulfide, which can also be found in tea. People may smell these compounds in tea and associate them with asparagus because they are present in post-asparagus urine.