Real Food Encyclopedia | Oysters

Jonathan Swift wrote that, “It was a brave man who first ate an oyster,” but no matter how many have since gone before, each of us who have looked upon the slimy, grayish, watery bivalves and screwed up the courage to slurp one down, despite its appearance, must be an adventurous sort. And nothing starts off a fancy (or romantic) meal better than a few oysters on the half shell, with their briny sweetness, their incomparable texture and their unique presentation.

Just looking at an oyster, one feels a sense of adventure and wonder about a natural world that could produce such a strange and delightful treat. Living as we do in a culture that produces increasingly novel but not very nutritious or interesting foods, oysters are a comforting throwback to an approach to eating at once simpler and more complex.

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What to Look for When Buying Oysters

First, look for oysters with shells that are not broken. If one is open, tap it; if it doesn’t close, toss it. Beyond that, what to look for depends on what type of oyster you like. If you prefer small and salty, go with West coast oysters, which also tend toward the sweeter side.

There are some great guides out there — this one urges you to figure out your oyster lover “type” and choose accordingly. Oysterpedia, a cool app, describes various types of East and West coast oysters, and allows you to make notes about varieties you come across.

Sustainability of Oysters

As seafood goes, oysters are among the few species one can ingest without guilt. Other shellfish may vary by region or how they were harvested, but overall, oysters are good for the environment. They provide a good alternative to land-based animal protein, and as bivalves, they help cycle nutrients in the water they live in, cutting down on pollution. Adult oysters filter 2.5 gallons of water an hour, or more than 50 gallons per day! Also, oyster reefs help protect coastal areas from flooding and erosion.

However, over reliance on mechanical harvesting can cause great damage to oyster beds. Even harvesting by hand is tricky — in natural beds (as opposed to tanks or cages), oysters pile up on each other, and when hurried harvesters remove large chunks of oyster bed, they harvest immature oysters and reduce the size of the reef, which also plays a great role in preventing coastal erosion.

Oyster Seasonality

As the old adage goes, it’s best not to eat oysters during months without any “R”s in them — in other words, summer. As mentioned in the nutrition section below, certain dangerous bacteria thrive in warmer weather, and before modern technologies like refrigerated trucks and chilled tanks, summertime oysters were more dangerous. The Pacific oyster in particular is said to be season-less, after clever breeding created sexless varieties that boast consistent quality year round.

Oysters and Geography

True oysters (as opposed to pearl or other varieties) belong to the Ostreidae family, which includes the genera Ostrea, Crassostrea, Ostreloa and Saccostrea. Like clams, mussels and scallops, oysters are bivalves, or aquatic mollusks with hinged shells. They’re found throughout the world’s oceans, usually growing in clumps, or reefs, in shallow coastal waters. They are filter feeders (eating mostly phytoplankton, but in the process, filtering and cycling nutrients in the water) and provide habitat for other fish.

Food oysters can grow pearls inside but usually don’t — pearl oysters are a different species, but it’s likely that oyster farming techniques developed alongside pearl farming.

There are a few different methods of cultivating oysters. All include the same early stage, where oysters grow loose to the size of “spat,” at which point they are ready to attach themselves to some form of substrate, referred to as a “cultch,” or in some cases, are allowed to grow a little larger, to be used as “seed.” This is where farmers come in and methods vary; one is to distribute seed or spat along existing oyster beds, another is to raise them in bags or cages held off the sea floor and the third to raise them in a specially prepared tank optimized for oyster production.

Ninety-five percent of the world’s oysters are farmed. China leads the world’s production, followed by Korea, Japan and the US. The US consumes about 60 percent of the world’s oysters.

Eating Oysters

Storing Oysters

Fresh oysters will keep in the fridge a few days, provided they aren’t sealed in plastic, or you’ll suffocate them. Once cooked, anything uneaten should go right back to the refrigerator.

Cooking with Oysters

Probably the most intimidating part of dealing with oysters is shucking them. Their tight, craggy shells can be tricky to open. Using the right knife and the right technique is key. Check out Molly Watson’s clear oyster shucking instructions on About.com.

Eat oysters raw or fried, grilled, in oyster stew, in oyster stuffing, oysters Rockefeller, oyster sliders, you name it. To be sure you’re eating them as safely as possible, discard any broken or chipped shells. If an oyster is slightly open, tap it with your fingernail and if it doesn’t close itself, toss it.

Oyster Nutrition

Oysters are really good for you — rich in protein, phosphorus, iodine, calcium, iron, and Vitamins A, B complex and C.

In a 2005 meeting of the American Chemical Society, scientists announced findings that raw oysters really do have aphrodisiac qualities, and that the amino acids that lead to higher levels of sex hormones is highest in the spring.

Eating raw oysters is not without risk. A really scary-sounding marine bacteria called Vibrio vulnificus occurs naturally, especially in low-saline areas like bays and estuaries, and is most common during warm summer months. The FDA recommends cooking oysters thoroughly to prevent getting sick. Your chances of contracting Vibrio vulnificus are relatively very slim, but they’ve increased: last summer saw twice as many reported cases than the year before, and affected areas are creeping north due to climate change.