Francis Percival advocates a more informed appreciation of the conventional matches, based not on geology or locality but on the physical properties of the wines and oysters themselves

There are few pleasures as visceral as a raw oyster, glistening on the half shell. It sits on its bed of crushed ice, alive until it is slurped, chewed, and swallowed. Our relationship with the oyster is primal: the only occasion when most of us will ever be directly involved in the dispatch of our own food. There is no civilized pretense standing between us and the saltwater whence the oyster came. This, we might imagine, is the taste of the sea.

More than that it is the taste of the sea somewhere-the taste of a specific rock pool at low tide. In a sophisticated restaurant, only the wine list will rival the oyster bar for its diverse collection of place names. In New York, we might see Long Island Blue Points, Delawares, Bristols, and Wellfleets; in London: Whitstable, Colchester, Carlingford Lough, and the Blackwater River. With oysters it is their sense of place that is their brand, and the concept of terroir is the key marketing tool.

And yet, despite this phenomenal diversity of piscine terroirs, it seems almost churlish writing an article about pairing wine with oysters. The answer just appears so obvious: a dry white wine of high acidity, light body, and moderate alcohol, which has seen little or no oak. Certainly, this is not a time to uncork a red wine. The briny shellfish magnify tannin and bitterness, so the pairing is doomed to end in an unpleasant, metallic mess.

Jon Rowley of Taylor Shellfish Farms in Washington State, one of the leading purveyors of oysters from the Pacific Northwest, sums up the perfect wine for oysters when he describes it as "white, cold, dry, crisp, and clean-finishing." Indeed, Taylor Shellfish has even gone as far as to sponsor an annual Pacific Coast Oyster Wine Competition, where the wines are tasted and rated for their capacity to accompany the shellfish; the judging criteria specifically look to "get away from vanilla and butter" toward something "dry, steely, [and] chilled to a crisp."

No, the real interest is not so much in what to drink with your oyster, but why you make that choice. Do you choose to reflect the local habit and drink Muscadet with your Belon oyster because they are both products of the Breton Atlantic coast? Or do you choose Chablis, grown on Kimmeridgian limestone rich in fossilized oysters? Both are splendid gustatory experiences, but it is how we attempt to connect and rationalize the pairing that reveals the most about our understanding of the concept of terroir. Do we opt for matches based on local habit and custom, or are we seduced into a geologically based approach dominated by a deeply entrenched and literal language of minerality?

Considering the oyster gives us the opportunity for a more sophisticated approach. The mechanisms through which the humble mollusk expresses a sense of where it is grown at once confirm and subvert any fixed concept of terroir; many of the most prestigious oyster beds are used only for the final affinage of shellfish sourced from other regions and, quite possibly, other countries. Like people, oysters reflect where they were raised, not where they were born. Instead of coopting problematic languages of locality or geology, we can rationalize our pairing in terms of the physical properties of the wine and the oyster. We will probably drink the same wine, but at least we will understand it better.

The oyster

The term oyster is used for a number of different bivalve mollusks, of which all that are of gastronomic significance are members of the family Ostreidae. Bivalves are simply creatures that live in two hinged shells; in addition to oysters, these include scallops, mussels, and clams. Oysters are greedy filter feeders, drawing water in over their gills through the beating of cilia. Suspended plankton and other food particles are caught in the mucus of the gills and transported to the mouth, where they are eaten, digested, and excreted. In this, oysters are the marine equivalent of penned veal or fattened goose liver-all they do is sit and eat. Each oyster can filter anything from one to six liters of water an hour, a feat broadly comparable to a human working his or her way through the contents of a large swimming pool each day. Unsurprisingly, oyster flesh is one of the sea's tenderest morsels.

Within the European and North American markets, these are the significant varieties: European oyster, Ostrea edulis In the UK, this is usually described as a native oyster, while in France it might be called a huître plate or Belon, in reference to the most famous source; in North America O edulis are commercialized as Westcott Bay Flats. The French name is genuinely descriptive of the flat, round shells, and the natural range is extensive, stretching from the Norwegian Sea right down to the Mediterranean.

Compared with its Asian and North American cousins, O edulis is a delicate beast, slow to grow and vulnerable to disease and exposure to air. While all oysters thrive best in highly productive estuarine and shallow coastal water habitats, O edulis prefer clear and cooler waters of higher salinity. They also take four to five years to grow to a marketable size, as opposed to three years for the commercially dominant Crassostrea gigas. UK annual production has fallen dramatically from more than 2,000 tonnes in the 1920s to 118 tonnes in 2004. 3 Nonetheless, European flats have an unrivaled intensity of flavor and easily sell at nearly twice the price of the more numerous gigas oysters.

Pacific oyster, Crassostrea gigas This is by far the dominant variety by market share in Europe, accounting for 90 percent of French and UK production. In the UK they are generally sold as rock oysters, while the French know them as huîtres creuses; in North America they are farmed in the Pacific Northwest and are known by their place of origin.

In theory this is a relative newcomer to European waters, since it was widely introduced through aquaculture in the 1970s, after populations of the Portuguese oyster Crassostrea angulata (the "portugaise" of so many French brasseries) were wiped out by a gill disease. However, recent work has confirmed that it is, in fact, an identical species. 4 Hardier and much faster-growing than the indigenous European O edulis, these do well on the lower shore and enjoy the warmer, brackish water of intertidal and subtidal areas. While the Pacific oyster is not as readily prized as its indigenous European cousin, it is highly adaptable, and its melon and cucumber aromas respond very well to expert affinage.

American/Eastern oyster, Crassostrea virginica These oysters have a vast range, stretching from New Brunswick right down to the Gulf of Mexico. Following the American habit, it is their place of origin by which they are known. An exhaustive list is unnecessary, but broadly speaking this includes almost all of the oysters grown along the eastern seaboard-from the novy in Nova Scotia, down to the Mississippi emerald point on the Gulf Coast. Oysters on the Pacific coast include the Totten Inlet virginica, found off Puget Sound. Like the Pacific oyster, the virginica is hardy and quick-growing.

Olympia oyster, Ostrea conchaphalia This is the native species of the Pacific Northwest, similar in both flavor and shell morphology to the European flat, but presented in a much smaller shell.

Kumamoto oyster Another small, delicate oyster popular on the American West Coast is the Kumamoto, originally from Japan's Kumamoto prefecture but brought over to the West Coast in the 1920s and subject to aquaculture ever since. These are tiny oysters with a sweet flavor that is not overly salty.

Through the prism of a bivalve's metabolism

Work on Ostrea edulis has demonstrated that the entire species exhibits profoundly low levels of genetic variation. As oyster beds were heavily exploited and declined in the 19th century, they were restocked with foreign populations, which caused a high degree of mixing of the natural oyster stocks throughout Atlantic Europe. 5 Differences in the flavors of oysters are differences in their terroir. Where aquaculture is from hatchery-produced seed, the same young oysters grown in different bays might be dramatically different. While Jon Rowley enthuses about his "uncommonly plump and sweet" Totten Inlet virginicas, the same oysters grown in Samish Bay and Willapa Bay disappoint him. Whereas the mechanisms through which vines articulate their terroir are notoriously understudied and vague, the demands of aquaculture mean that we can be more precise about how oysters express differences in their environment in terms of flavor.

Oysters do not store energy in the form of fat. Instead, they accumulate other amino acids-proline, arginine, alanine, and some combined forms-as well as glycogen, the animal version of starch. Although glycogen is itself flavorless, it is slowly transformed into sweet sugar phosphates. This is the distinctive sweetness of a plump oyster.

The vast range of the virginicas on the American East Coast provides a very useful example of the impact of different water temperatures on the same oyster. Forget the Mason-Dixon Line, for it is in their oysters that we see the real cultural divide between the American north and south. Yankee oysters from New England and Long Island grow slowly in cold water and take on deep, sweet-salty flavors; they are, a Southerner would contend "too strong and crisp," and austere New Englanders rarely eat them in any way other than raw, on the half shell. In contrast, the warm waters and plentiful food of the Gulf Coast will grow an oyster to a marketable 3 inches (7.5cm) in just 18 months, at the expense of bland, soft, mild flesh. Yet these oysters are ideal for cooking and will lose almost no weight from the heat-a characteristic acknowledged by the extensive repertoire of cooked oyster dishes in the cuisine of Louisiana and its environs. Water temperature even controls the sexual cycle of the oysters; warm water speeds development into a plump female, creamy with millions of tiny eggs, whereas the slow growth in cold water might indefinitely postpone sexual maturity and give a leaner, crisper texture.

In addition to water temperature, the salinity of the water has a profound impact on the oyster's taste. For example, the brackish water of the Aspy Bay in Nova Scotia gives a delicately light-tasting virginica, whereas the same oyster grown in Colville Bay on Prince Edward Island would be salty, meaty, and plump. Because oysters breathe and swallow seawater, they need a method of maintaining the appropriate concentration of dissolved substances in their bodily fluids.

Ocean water is 3 percent salt by mass, while the optimum total level of dissolved minerals in animal cells is less than 1 percent. In order to preserve this osmotic balance, oysters fill their cells with amino acids, especially the savory and mouth-filling glutamic acid that produces umami flavors. The saltier the water, the more savory the oyster. Much Asian ostreiculture is to make oyster sauce that exploits just these properties of mollusks for a deeply umami condiment.

The greatest factor in making oysters taste different from one another is, of course, their food supply. The French make the most sophisticated use of dietary manipulation in the claires of Marennes-Oléron: For their final stage of affinage, oysters are placed in shallow pools (claires) formerly used for salt mining. The spring tides fill the claires with seawater, which is left to stagnate and grow algae, forming a rich and nutritious soup that is much to the oysters' liking; they fatten readily, and their flavor becomes increasingly nutty and refined. Famously, the micro-algae species Navicula ostrea will even turn the oyster's flesh green in testament to its protracted fining.

A flexible concept of terroir

With oysters, it would appear that the taste of place is absolutely everything. Well, yes and no. Human artifice, greed, and pragmatism in the face of ecological disaster all adapt terroir characteristics. As we have seen, the Ostrea edulis is extremely vulnerable to disease, and European stocks have been savagely hit by the parasitical disease Bonamiasis. Mortality rates of 80 percent have been reported, devastating the French industry when it first impacted in the 1970s, with production falling 83 percent by 1982. We are fortunate enough that in the UK there is less than a 1 percent prevalence of the disease in the O edulis stocks in the Solent off Southampton. However, the industry survives in Essex only through the relaying of part-grown Solent oysters for growing on to market size in just one growing season; even holding the oysters on their Essex beds for just one more year results in mortality figures of 75-90 percent. If modern Colchester natives have only lived in Essex for a maximum of seven months, does that mean that they are less expressive of their creeks and estuaries?

On the contrary, the habit of moving oysters to different waters for breeding, initial growth, and finishing is an ancient one. The River Belon itself is better regarded as a finishing school for oysters, rather than a permanent home. French ostreiculture is thoroughly divided into those who coax the bivalves through their first stages of life and those who prepare them for market; the oystermen of the Arcachon Bay do little but the former. While most European water is too cold for Pacific oysters to spawn, the warm water of Arcachon is perfect; the larval oysters must then be transferred to cooler water, where they can develop greater complexity of flavor.

Eleanor Clark's classic and poetic account of Breton oystermen, The Oysters of Locmariaquer (Pantheon Books; 1964), deals with the initial growth of les plates that will eventually be passed on for final affinage and sold as Belons. Oysters require a more flexible conception of terroir, where human intervention is as essential a component as the substrate or microclimate. While a raw oyster on the half shell positively screams its sense of place, it is most likely the product of pronounced and considered human involvement; the oyster might well have been moved hundreds of miles in its lifetime, yet still it will taste absolutely distinctive. Is this so very unlike a wine? Great, site-distinctive wines are also crafted by human artifice. From biodynamic agriculture to drip irrigation, it is the interaction of man and vine that makes the wine-not the plant alone.

Here a wine-pairing strategy based on strictly local traditions begins to fall down. Which tradition? What should you drink with your Whitstable-native oysters if they are actually relaid seed oysters from Brittany? Do you opt for a dark London porter, whose iron-tinged roasted malts highlight the rich metallic taste of the oyster? Or some Muscadet that throws the briny bivalve into sharp relief with razor-edged acidity? Both are natural and organic expressions of the environments in which the oyster has grown.

There is just one unfortunate shellfish-industry practice for which we should stay alert, since it subverts any notions of terroir in pursuit of a fast buck. Unless the oysters have grown in the very cleanest of water, their final stage before they go to market is to be depurated: The oysters are put in a pond or tank, and clean water is passed over them for a couple of days to rid them of any minor bacterial contamination. For this purpose, unscrupulous oystermen can use artificial seawater, much to the detriment of their shellfish. Artificial seawater is dechlorinated, resalinated municipal tap water, and it can have a disastrous impact on the flavor of the oysters; the liquor becomes devoid of complexity and reflects the fact that it is just salty tap water.

Even worse, more delicate varieties like the European flats, Olympias, and Kumamotos are so sensitive to the change of water that they begin to gape open and die. Proper depuration should be done in the water in which the oysters were grown, carefully filtered and with ultraviolet lights to kill any troublesome bacteria. Avoid artificial seawater at all costs.

The lure of geological reductionism

When it comes to the wines of the Kimmeridgian chain, it is seductively tempting to explain why Chablis, Sancerre, and their ilk are happy oyster wines by mentioning that the limestone of the vineyards is rich in fossilized oyster shells. The implication is that there is something in the ground that is processed by the vine to engineer a harmonious pairing; in effect, the wine becomes more oyster-like. Even when not in the context of fruits de mer, it is remarkable just how often Chablis receives an oyster-based tasting note. Consider these two examples, found via Google, using the words "Chablis" and "oyster":

François Raveneau 2002 Chablis Grand Cru Les Clos

Medium saturated yellow-gold color. Lovely oyster-shell nose, with citrus fruit and a "green" component that recalled the grapefruit quality found in many Sauvignon Blancs...

Howard Kaplan and Robert Millman, co-directors, Executive Wine Seminar Inc, www.erobertparker.com

Domaine William Fèvre 2003 Chablis

Pale yellow. Honey and pear on the nose. Fat, oily, sweet, and accessible. Rich flavors of mint, and oystery, iodiney reduction. Nicely balanced and plenty ripe.

Stephen Tanzer, Stephen Tanzer's International Wine Cellar, www.wineaccess.com

The selection of these particular tasting notes is relatively arbitrary, and there were plenty of other options; it passes no judgment whatsoever on the critics involved. However, we might wonder how the same characteristics might be recorded in a wine away from the oyster shells of the Kimmeridgian chain? More significantly, would the same quality in a Mosel Riesling be reported as tasting of "slate"? Our language of terroir can be alarmingly literal and overemphasize the geological. An invocation of oyster shells is usually an effort to pin down the perceived minerality of the wine, but oyster shells in themselves do not smell of minerals-they smell of the sea. The rich smell of the sea coast appears to be provided by bromophenols, which are synthesized by algae from the bromine in the seawater. The action of the waves propels bromophenols into the air at the coast, where we smell them; oysters accumulate them by eating algae. 10 An instructive, if unscientific, exercise is to try two oysters, one slurped from an inert vessel and the other straight from the half shell. You realize the extent to which the flavors that we associate with eating oysters are actually volatile vegetal compounds on the outside of the shell. No wonder an oyster tastes like a rock pool. You have brought your own mini rock pool home in the form of the shell.

Ironically, that there should be such fossil deposits in the limestone of Chablis is not surprising, and it reflects the mineral needs of the oyster, which has to be able to extract lime from the water in order to grow its shell. The great innovation of 19th-century American ostreiculture was to dump oyster shells back into the oyster beds. As the sea broke down the shells, other oysters would absorb the lime.

Physical properties: acidity and salt

If we are to understand why successful oyster wines work, we need to look at how their physical properties interact with those of the oyster. Returning to the judging criteria from the Taylor Shellfish Farm Oyster Wine Competition, it is striking how frequently they use descriptors emphasizing the austere, flinty dryness of the wine, together with the need for a certain perceptible minerality.

As the case of the oyster-shell Chablis illustrates, "minerality" is a tricky proposition, but we might follow Professor Ann Noble from UC Davis and think rather in terms of high acidity and an absence of clear fruit flavors, rather than worrying about explaining a mechanism through which vines might metabolize the taste of stones. 12 All of our potential oyster wines exhibit pronounced acidity, and such a focus would also reflect the two most common condiments for oysters: lemon juice and shallot vinegar.

Why is acidity so desirable when eating a briny oyster? We know from laboratory experiments on rat epithelials that neural responses to salt are reduced in the presence of acidic stimuli. 13 However, things become less clear when examined from a sensory, rather than a physiological perspective. There might be fewer neural responses being generated, but what do we actually perceive? Of three studies into the interaction of high concentrations of NaCl and tartaric acid, two suggest that there was a mutually suppressive effect, while, frustratingly, one reports no effect at all. Despite the differences between laboratory conditions and the dinner table (not least in that we get to drink complex wines rather than aqueous tartaric acid solutions), there is enough evidence to support at least a provisional conclusion: that the oyster and wine make a synergistic match because the wine reduces the overpowering saltiness of the oyster, and the oyster dulls the strikingly aggressive acidity of the wine. In effect, the wine lifts the oyster from its salty shroud, allowing us to taste the shellfish itself more clearly. All of which confirms our original and instinctive choices of wine-not just Muscadet, Chablis, Champagne, and Sancerre, but also drier German Riesling, Picpoul de Pinet, white Graves, and young Hunter Semillon.

To demonstrate, we might consider a little thought experiment. Let us think of a major wine-producing region, where the best terroirs are based on the crushed shells of fossilized sea creatures-though, in this case, chalk-and connected to the oyster beds of the Gironde, the Ile de Ré and the Ile d'Oléron. Surely the wine would be the perfect accompaniment to some rich, plump oysters? After all, this must be the ancient local practice! And the geology must make the wine sing with appropriately mineral complexity! Unfortunately, this region is Cognac. Even if we are to break the traditional digestive taboo on the eating of raw oysters with spirits, the pairing is just plain nasty-raspingly bitter and metallic.

But then, we think, what would happen if we made a dry table wine from some of the Ugni Blanc? We would pick early to retain freshness, handle reductively, and the wine would see no oak; it would be lean, austere, and acidic. And an oyster wine is born...