Oysters, or gul in Korean, are sometimes called “the milk of the sea” or “the ginseng of the sea.”They are a popular food enjoyed by people around the world. Koreans love seasoned andfermented oysters, and also enjoy oysters prepared in various ways such as oyster pancakes,oyster soup or oyster rice. These bivalve mollusks are rich in nutrients and even help repairthe marine environment, making them useful all around.
Most Koreans are familiar with the lullaby “Island Baby” (Seomjip agi). A song loved even by adults, it describes a baby falling asleep while waiting for its mother, who has gone to pick oysters. But Koreans’ knowledge of oysters goes far beyond a lullaby. Their prehistoric ancestors ate these nutritious marine mollusks, as evidenced by shell mounds found along their seashore. Working in the field of malacology, dealing with clams, gastropods and snails, you could say I’m quite familiar with oysters myself.
While collecting research materials along the seashore, I often meet women picking oysters and chat with them about this and that. I find it interesting that even as we talk, they never stop working. It’s amazing to watch their dark suntanned hands ceaselessly gathering oysters attached to the rocks, so fast and sure-handed. You could never dream of using your hands the same way. With an iron hook, they strike the hinge between the oysters’ two valves, quickly lift the upper valve, hook the milky-white inner flesh, and drop it into a container. Performing this movement with lightning speed and precision, they are masterful indeed.
The left-hand valve of the oyster sticks flat onto rocks, whereas the right-hand one bulges a little. Koreans call oysters “oyster shell” (guljogae), “stone oyster” (seokgul) or “stone flower” (seokhwa). Among these names, stone flower may sound a little odd. From a distance, however, the whitish left-hand valves, stuck on the flat dusky rocks after the right-hand valves are lost, resemble flowers blooming on the stone.
Preserving the Marine Environment
Wild oysters living attached to stones and rocks on the seashore are called eorigul, meaning “young oysters,” and used to make seasoned and fermented oysters called eoriguljeot. Just imagining the salty and spicy oysters and a bowl of steaming white rice makes my mouth water. The word eori comes from eorida in Korean, which means “young” or “small.” Names such as eoriyeon (aquatic plant of the species Nymphoides indica), eoriyeochi (long-horned grasshopper, Prosopogryllacris japonica) and eorihobakbeol (carpenter bee, Xylocopa iculata circumvolans), all follow a similar naming principle.
The oysters found along the Korean coastline are classified into three genera and 10 species, and these live in the area where seawater and freshwater mix, in the intertidal zone where high tide and low tide alternate, or under the sea down to 20 meters deep. Oyster shells are not as smooth as other kinds of shells but sharp, like rough scales. Oysters are bivalvia, living organisms with two valves, and they are also called pelecypod (Pelecypoda) as their feet look like a double ax, or pelekys in Greek. In intertidal zones, oysters close their right valves tight at the ebb tide and open them at the flood tide.
Oysters are filter feeders that breathe and feed through their gills. A single oyster filters up to five liters of sea water per hour, catching organic materials containing nitrogen, phosphoric acid, plankton and bacteria, thus helping prevent the pollution of sea water through excessive eutrophication. As such, oysters are environment-friendly living organisms.
Healthy Food Preventing Lifestyle Diseases
Oysters traditionally used in Korean cuisine, including seasoned and fermented eoriguljeot, are flavorful and full of nutrients. Over the ages, oysters have been a stamina food, often called the “the milk of the sea” in Japan, much like Koreans’ description of oysters as “the ginseng of the sea.” Oysters are rich in zinc, a mineral necessary to maintain healthy levels of the male hormone testosterone. They also contain selenium, iron and calcium, and are rich in Vitamin A, B12 and D. This makes oysters a healthy food that helps prevent various lifestyle diseases, such as high blood pressure, stroke, hardening of the arteries, or liver problems.
Oysters can be eaten raw or cooked in various ways, such as oyster sauce, seasoned oysters, oyster rice, oyster soup, braised oysters, and oysters pan-fried in egg batter. They are also used as an ingredient in kimchi. And of course, the soft flesh means oysters can be eaten easily by the elderly whose teeth can no longer withstand tougher foods.
While oysters can be eaten in many different ways, traditional wisdom in the English-speaking world warns against eating them raw at certain times of the year. According to the so-called “r-month rule,” one can safely eat raw oysters harvested in the months with an “r” in their names, that is, the months from September to April. From May to August, it is recommended to cook oysters before eating them, which is probably a good idea since those warm months comprise the “poisonous” breeding season, when various marine bacteria thrive. However, if the breeding waters are clean enough and modern refrigeration is used, oysters may be eaten raw all year round.
The growing demand worldwide cannot be met by wild oysters alone, so oyster lovers have turned to cultivated oysters to satisfy their appetites. The baby oyster, or spat, grows to about 7 centimeters and weighs about 60 grams by the end of its first year, then to about 10 centimeters and 140 grams by the end of its second year. Afterwards its growth slows down. Oysters usually fertilize and spawn between May and August, and the eggs float around before they become spats, which then attach to rocks, stones, or other oyster shells.
Oysters are rich in zinc, a mineral necessaryto maintain healthy levels of the malehormone testosterone. They also containselenium, iron and calcium, and are rich in Vitamin A, B12 and D. This makes oystersa healthy food that helps prevent variouslifestyle diseases.
A nutritious and flavorful food, oysters can be prepared in various ways for dishes such as oysters pan-fried in egg batter (guljeon, top) and seasoned and fermented oysters (eoriguljeot). Oysters can also be eaten raw, dipped in seasoned soy sauce or red pepper paste with vinegar.
Farming Methods Determine Taste, Texture
Oyster farming is usually conducted by attaching oyster shells in clusters to thick s and leaving them to hang under water. The southern sea around Tongyeong, South Gyeongsang Province, is best suited to this farming method, thanks to its moderate temperature in winter and the low tidal difference and gentle waves around its many islands. In the West Sea, with its vast mud flats, oysters are cultivated by a method known as “throwing stones,” which involves scattering flat stones across the mud flats, or the “rack and bag” method, where spats are put into mesh bags and left on racks.
Oysters farmed through the “throwing stones” or “rack and bag” method are exposed to scorching sun in the summer and biting wind in the winter, like wild oysters. Living organisms exposed to a harsh environment accumulate special nutrients in their bodies. As a result, they are tastier than those farmed in the South Sea, which are kept under water most of the time. Much the same happens in the plant world. Wild plants are healthier than farmed ones because they produce specific types of phytochemicals needed to survive harsh environments. In the human world, too, those who become successful after a tough childhood are often more mature and caring.
In most people’s minds, oysters may be inseparable with pearls. Pearls are produced when an alien substance is sucked into an oyster and gets stuck between the shell and the mantle (which covers the oyster flesh). The mantle then secretes nacre, or mother-of-pearl, to coat the alien substanceupon , and thereby protect itself. When the nacre is ed over several years, it forms a natural pearl.
Pearls, Just Plain Calcium Carbonate
This process is artificially imitated. Thick freshwater shells are cut into small pieces and ground into tiny spheres that are inserted between the shell and the mantle of the pearl oyster to cultivate pearls. But no matter how valuable pearls may be to human beings, when observed through a microscope they are just plain calcium carbonate, much as a diamond is just a very hard piece of carbon.
Regularly exposed to sun and wind, oysters from the mud flats of the West Sea have more flavor and texture than oysters from the South Sea, where they remain continuously under water.
Kwon Oh-kilProfessor Emeritus, Department of Life Science, Kangwon National University
한국국제교류재단
