Asparagus, coffee, and tea

Had a fascinating experience the other morning. Bought a lightly roasted coffee called Stargazer from our local specialty coffee roaster, Gimme!. Flavor description from the package: "dark chocolate, bourbon cherry, caramel, stone fruit sparkle."

Stargazer coffee beans—notice the light color and lack of oil, indicative of a light roast.

I got the chocolate and maybe the caramel, certainly the sweet, but was overwhelmed by the coffee's vegetal taste — clearly asparagus. It even had that sweetish asparagus after-taste, all of which led me on a hunt for understanding how these flavors came to be in the coffee...and in green and oolong tea, too.

As I said in my book, "Three Basic Teas & How to Enjoy Them:"*

"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 typical compounds in asparagus, the most abundant is dimethyl sulfide. This compound can be present in green and oolong tea, where it contributes a “marine/seashore/oceanic” quality. But if you associate that smell with cooked asparagus, then you would say it’s an asparagus smell. You could also associate that smell with the odor of urine after eating asparagus—the people who have the gene for breaking down asparagusic acid excrete dimethyl sulfide among other compounds."

Dimethyl sulfide doesn't give the asparagus aftertaste, however. Another sulfur compound that could be a candidate: methionyl acetate. It's in both coffee and asparagus, and beer, too. But it doesn't give a sweet aftertaste as far as I can tell.**

Perhaps the sweet aspect comes from an entirely different set of compounds, the pyridines, which abound in coffee, especially with light roasting. Pyridines can be sweet, even too sweet, though many also have a grassy quality. Turns out that 2-ethyl pyridine gives a sweet yet green grassy quality to asparagus—in fact, some people consider it to be "the" asparagus scent. (Worth noting that it is in black tea as well.)

The conclusion I reached from this hunt (and so many others) is that foods from plant materials such as tea, coffee, and asparagus, share a host of basic chemicals—the resulting flavors may well simply depend on which chemical stands out in the mix. 

* You can get a copy of "Three Basic Teas & How to Enjoy Them" either from the printers:  https://www.createspace.com/6961595, and get a 10% discount using the code V97A7SQ3; or from Amazon—sorry, couldn't get a discount with them.

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