Before diving into a discussion that stirs up memories of agony (high school science classes), I’m going to start with a quote from The Phantom Tollbooth by Norman Juster. The Phantom Tollbooth, by the way, is an excellent book—my Dad first read it to us many years ago, and I remember learning, among others, the words “lethargic,” “dodecahedron,” and “unabridged.” It is about a boy, Milo, who is always bored, until one day a mysterious box appears in his room: the Phantom Tollbooth. He drives through it, and adventure—and a growing love for learning—follow. The quote comes from the time Milo visits the Valley of Sound, which is completely silent because the Soundkeeper took away all sound as it became evident that the Valley’s population had quit caring about sound, and only were interested in the ugly noises of economy, destruction, etc. He visits the Soundkeeper, and finds her sitting in front of a radio. She says: “Isn’t that lovely?...It’s my favorite program—fifteen minutes of silence—and after that there’s a half hour of quiet and then an interlude of lull. Why, did you know that there are almost as many kinds of stillness as there are sounds? But, sadly enough, no one pays any attention to them these days. Have you ever heard the wonderful silence just before the dawn?...Or the quiet and calm just as a storm ends? Or perhaps you know the silence when you haven’t the answer to a question you’ve been asked, or the hush of a country road at night…or, most beautiful of all, the moment after the door closes and you’re all alone in the whole house? Each one is different, you know, and all very beautiful, if you listen carefully.”
Lovely. And now for the chemistry part. Did you know that there are a ridiculous number of acids, and that the taste of coffee is quite dependent on them? And that these same acids are found in other natural edibles—such as apples or citrus—which explains why, when you sip your coffee, you may detect the flavor of lemons or berries--? I may be completely out of my depth here, but am going to try to make sense out of the “Coffee Acidity” section of Ted Lingle’s The Coffee Cupper’s Handbook.
Here are the first two points: 1) Coffee is actually less acidic than most alcoholic beverages (gin and vodka are exceptions), juices, and sodas—really, anything you’d typically drink other than water, milk, or tea (though tea is close to coffee in acid content). Which is interesting, because I think coffee’s reputation suggests otherwise.
2) “Acidy” and “Acidity” are not the same things. “Acidy” refers to a sweet taste sensation, and relates to how sugars in the coffee combine with certain acids. Other acids, however, interact with other components and may produce sour, salty, or bitter taste sensations. (Sweet, sour, salt, and bitter are the four basic tastes).
Here is the outline version of Coffee Acids:
I. Amino Acids—influence sweet sensations
II. Phenolic Acids—influence bitter sensations, includes caffeic acids
*Chlorogenic Acids—it is the decomposition of these acids that results in the
unpleasant (overly bitter/sour) taste of coffee that has been sitting around
too long. So, when you enjoy a cup of fresh-brewed coffee, thank the
chlorogenic acids.
III. Aliphatic Acids—influence sour sensations—and others
*Tartaric
*Citric--citrusy
*Malic—apple-like
*Lactic--buttery
*Acetic—fruity—also, too much acetic acid results in a fermented taste. (Acetic
acid is not inherent to the bean, but is formed when the beans for a wet-
processed coffee are fermented. Fermentation is one step in the process
of separating the coffee bean from the fruit of the coffee cherry.)
Again, the word “Chemistry” is one that I typically think of with horror or disinterest. The words “chlorogenic” and “aliphatic” have no meaning for me—yet—but, thanks to coffee, it has become a personal goal to be able to drink a cup and identify, “oh, an apple sensation—malic acid” or “this coffee must have more citric acid, and reminds me of grapefruit.”
Why? Think of all the citrus fruits, the different varieties of apples, different butters, berries, etc—and how each time you taste one of these, you’ll have a flavor memory that a future cup of coffee may bring to mind! And these are just tastes that came up because we were talking about acids! If we talked about sugars, think of all the different kinds of chocolates or caramels—or aromas, flowers like jasmine and lavender, spices—cinnamon, vanilla, cloves—it is incredible how all these organisms relate to one another, and I must grudgingly owe a debt of gratitude to chemistry and things like chlorogenic acids. And happily go to the grocery store to buy a pineapple, so as not to miss a potential pineapple note in my next cup of coffee :) Hooray for flavor!
So that’s acids--I know I left some holes in the explanation, so if you have any questions…or corrections…let me know, and I’ll see what I can find out!
