Fri 1 Jun 2007
“From (a) chemical point of view, wine is an acidic aqueous ethanol solution with aroma compounds.” Gosh, that sort of takes the thrill out of your $12-glass of Sonoma-Cutrer Les Pierres Chardonnay 2005. Might as well define Uma Thurman as a carbon-based, water-logged mammalian sack of DNA.
The truth is — ready? — all material things are composed of chemicals, and a bottle of great wine, about which we might rhapsodize so lyrically and which we may elevate to sensual, cultural and economic pedestals, is naught but a glass container filled with about 85 percent water (more or less), 12 or 13 percent alcohol (more nowadays) and 2 or 3 percent highly complex chemical compounds. It’s those minute traces of chemicals that give wines their most desirable characteristics. Well, we need the alcohol for the buzz.
I know, you’re thinking, “Jeeze, this killjoy is fixin’ to take all the fun and magic and romance outta wine.”
I wouldn’t do that, being a firm believer in the fun and magic and romance of wine, but I also think that we who love wine — consuming it and writing about it — ought to know more about what wine really is, whence its attributes derive and how it makes them known.
To this end I have been reading — well, reading isn’t the correct word because much of this book is impenetrable to the normal person with an advanced degree — reading at a collection of papers called The Chemistry of Wine Flavor, edited by Andrew L. Waterhouse and Susan E. Ebeler, published by the American Chemical Society Symposium Series in 1998 and distributed by Oxford University Press ($35).
We learn, for example — and there will be a test — that when we swirl a glass of wine and unleash its inimitable aromas into the air and into our noses, our sensing agents are being stimulated by 600 to 800 distinct volatile compounds, the primary source of which is the fermentation process. These compounds may be divided into five groups: alcohols; esters; carbonyl compounds (aldehydes and ketones); sulfur-containing compounds; and organic acids.
The particular flavor of a varietal wine — and don’t forget that most of what we describe as flavor is actually aroma — whether sauvignon blanc or chardonnay, cabernet sauvignon or pinot noir, is the result of a very complicated series of transformations that begin at root-level in the vineyard, continue through the maturing and ripening of the grapes and speed up exponentially during the relatively violent and energy-releasing processes of crushing, maceration and fermentation. I mean, imagine if you were an innocent little grape that came to the big city and all that happened to you; you would probably turn out to be a cheap, scuzzy muscatel, living in the gutter, and blame it on your childhood.
The hint of herbaceousness that sometimes characterizes cabernet sauvignon and merlot wines? That derives from the volatile short chain aldehyde called 3-Methyl-1-butanal, other wise known as isovaleraldehyde, which I guess is the name-brand version. The cocoa or coffee-like undertones we sometimes detect in red wines? That’s 2-Methyl-1-butanal. What a difference a molecule makes! The more pronounced herbaceous elements of sauvignon blanc, that bell pepper, green bean, gooseberry quality, comes from methoxypyrazines, actually from three methoxypyrazines, but we won’t go into that except to say that one of them, the most abundant, of course, is responsible for the canned asparagus nature of sauvignon blancs that have crossed over to the dark side. This is why canopy management is so important in the farming of sauvignon blanc vineyards. Look, there’s an isobutal-methoxypyrazine now! Cute l’il fella. Simple and elegant.
The previous paragraphs merely skim the surface of a fount of knowledge that grows ever deeper as more research is done into the physical mechanics of wine. We haven’t mentioned color, the result of a range of anthocyanin pigments and pigmented tannins (created by the interaction of anthocyanins with catechins, proanthocyanidins and ellagitannins), nor have we touched on the chemistry of tannin itself, the proanthocyanidins, while the bitterness and astringency associated with large amounts of tannin derive from flavonoid polyphenolic compounds. And those polyphenolic compounds, oh my god, what a rich stew of influences they bring to the color and texture of wine! And I haven’t mentioned the broad range of glycosides, a two-molecule linkage of which one molecule is a sugar and the other, well, isn’t, but may be our old friend the anthocyanin. The point is that in their many combinations “grape glycosides are of fundamental importance to wine flavor,” as one of the essays in Chemistry of Wine Flavor states, affecting such elements as apple, floral notes, honey, dried fig, chocolate and tobacco.
What’s actually important about this dizzying array of chemical compounds and their almost infinite sway of interactions and transformations is that the more that scientists delve into the inner workings of grapes and the fermentation process the more tools they acquire for learning how to analyze and gauge the potential to influence through chemistry the quality of the wine while the grape is still on the vine. Already the “glycosyl-glucose assay,” introduced in the late 1990s, is being used in vineyards and wineries to test such theories and practices.
So, keep all of this information in mind the next time you tiptoe down the winding stair to your cellar, extract a dusty bottle of Cheval-Blanc ’49 from its niche and guide it, like Orpheus tenderly leading Eurydice, back to the light. Whatever people have said or written about the wine, it’s just a bottle filled with water, alcohol and more seething chemical compounds than you could shake a stick at or even want to think about. Forget about drinking the stuff and send it to me instead. I’ll run a few tests for you, have a sip or two, let you know how it works out. Oh, and tell Uma.
The image of isobutylmethoxypyrazine is from flavornet.org.
The image of the glass of white wine is from cleehouse.com.
And the image of Uma Thurman is from — and I’ll provide the link here; many of you will thank me — venus.provocateuse.com.