One of our favorite meals is a plethora of oysters on the half shell accompanied by an abundance of hot, crispy French fries. An afternoon spent slowly sliding cold briny oysters down our throats interspersed with bites of crunchy, salty potatoes is one well spent. Oysters can easily be enjoyed either raw or cooked. Slicked with cream and spiked with chilies they can be a warm soothing spoonful on a rainy afternoon. Happily oysters are sustainably farmed shellfish and their industry has a minimal impact on the marine environment. That makes eating them a good thing for everyone involved, except perhaps the oyster.
Pearl oysters are not the same as food oysters, so there’s no possibility of finding the rare perfect jewel in your dinner. The oyster you consume may contain a tiny pearl but it comes from a different family entirely. Edible oysters are from the Ostrideae family and are scattered in waters throughout the world. Two of the most popular varieties are the eastern American oyster, Crassostrea virginica, and the Pacific oyster, Crassostrea gigas. The first variety is found in the waters of the Atlantic Ocean and the second in the Pacific. There are variations of these two species found from New York to Australia and everywhere in between. The three other cultivated species are the Kumamoto known as Crassostrea sikamea, the European Flat or Belon named Ostrea edulis, and the Olympia, otherwise called the Ostrea conchaphila.
Oysters grow best in areas where fresh water and salt water mix in spots that are protected from waves and storms. They tend to be oval or pear-shaped although their structure can vary depending on what they attach themselves to. Oysters reproduce in one of two ways. The European and Olympia oysters are hermaphrodites. Eggs are fertilized within the body and then carried in the gills for twelve days until larvae or spats form. The oysters from the Crassostrea branches begin life as males and then become female. They may change back and forth a few more times over their lifespan but remain primarily female after that first change. Females release eggs directly into the water and males do the same with their sperm. When the two cross paths the eggs are fertilized. These fertilized eggs mature into larvae in the water. Once the larvae have formed they swim through the ocean currents for two to three weeks, developing the beginnings of their shell, until they settle and attach themselves to a home using their sticky foot. There they remain until they are harvested and eaten by man or some other predator.
While oysters are not able to move by themselves, they can be dislodged by the pull of the waves. Their hinged shells are rough and irregular looking. The bottom shell is the one attached to their mooring, it is more curved and cup-like than the top. The shell itself is formed in layers with calcium carbonate in chalky middle and nacre, better known as mother of pearl, forming the smooth inner lining. The hinge is connected to the two halves of the shell with two ligaments. When the inner adductor muscle relaxes, the shell can be opened and closed using the ligaments.
Looking at a raw oyster you will see the visceral mass as the rounded center, which contains the stomach, intestines, and other internal organs, and the round, firm adductor muscle. The adductor muscle controls the opening and closing of the shell. The oysters body is covered by the three delicate layers of the mantle. The outer layer is responsible for the secretions that form and calcify the shell. The inner layers are comprised of muscle, blood vessels, and nerves covered by epithelium. They collect sensory input and relay it through the system. The mantle aids in reproduction by facilitating the release of the eggs. The mantle aids the gills in respiration, produces and secretes mucous, and supports elimination. Underneath the mantle around the outer perimeter are two curved pieces, one longer than the other. The longer piece that looks like it is imprinted with a delicate fringe is composed of the gills. The smaller piece is the labial palp.
Oysters filter feed by extracting food particles and algae from the water through their gills. They consume extremely small plant and animal specimens, larvae, and spores. The gills are covered with hair-like structures known as the cilia. The cilia beat on the gills, drawing in water and filtering it for nourishment. Food is sorted by the labial palp. Particles too large for consumption are passed to the edge of the mantle to be ejected from the shell. Smaller particles are passed down to the mouth and then carried through a short esophagus to the stomach. There it is digested and passed through the intestines where nutrients are absorbed. Finally feces are expelled back out into the water. It is a surprisingly complex process for something so tiny and innocuous in appearance.
One of the main issues with eating raw oysters is the texture. People either love them or hate them. There isn’t much space in between those two stances. They are undeniably slippery and soft, salty, sometimes creamy, sometime mineral-y, slightly sweet, and to our minds, delicious. Our years in fine dining kitchens have led us to cleaning raw oysters for use in composed dishes. We would shuck the oysters and save the juice. Then we would trim around the visceral mass, that plump centerpiece, removing the mantle, the gills, the labial palp, and all of their myriad parts. We would use the oyster liquor and the trimmed meat to make a sauce to highlight the smaller, single bite of the trimmed oysters.
When we were working in Maine we were lucky enough to get oysters delivered to us from down the road. Jeff was our oyster guy, Pemaquids were his bounty. Because we were local, he introduced us to jumbo oysters. These beauties came in shells that were almost a foot long. The oysters inside were large but not as gargantuan as the shells would lead you to believe. These plump beauties were singularly delicious and succulent. We used them to make a version of Oysters Rockefeller that was served in the giant bottom shells and the presentation was as popular as the dish itself. You will only find oysters this large close to their source because the cost of shipping the heavy shells makes them prohibitively expensive anywhere else.
As chefs we are always looking for ways to make food taste better. Sometimes that means making it more approachable. After all if diners wont eat something it doesn’t matter how good it is. We came up with the idea of gently poaching the oysters to firm up the flesh while still retaining the fresh briny flavor of the raw product. We don’t cook them for long, we simply shuck them and cook them sous vide with their juices in a 48°C/118°F water bath for twenty minutes. Then we ice them down to stop the cooking process. Finally we trim the poached oysters, separating out the liquid and the trim, and see where inspiration takes us. The low temperature cooking allows the oysters to plump up and sets the flesh to eliminate the slippery texture that many people find unpleasant. They still have all the flavor of the raw oyster with the added benefit of a silky, resilient texture. In fact we have convinced a few confirmed raw oyster haters to enjoy oysters on the half shell with these softly cooked beauties.
Once the oyster has been poached we strain the juices and store the oysters in it. We use these oysters in both cooked and raw preparations. We’ve found that the poached oysters retain their shape and do not shrivel up or lose their shape when we cook them again. They fry up beautifully and we can use the liquor as the basis for a tart, briny vinaigrette to dip them in.