Fermented skate is a Korean delicacy made from raw skate fish that has been aged at low temperatures until its flesh becomes intensely pungent with ammonia. Known as hongeo-hoe in Korean, it is one of the most powerfully aromatic foods in the world, often compared to Swedish surströmming for its ability to clear a room. The dish holds deep cultural significance in South Korea’s southern Jeolla province, where it has been eaten for generations and remains a centerpiece of celebrations and special meals.
How Skate Fermentation Works
Unlike most fermented fish products, fermented skate requires no salt, brine, or added bacteria. The process relies entirely on the fish’s own biology. Skate are cartilaginous fish, meaning they have no true bones. Like sharks and rays, they regulate their body fluids using urea, a nitrogen-rich compound stored throughout their muscle tissue. When the fish is left to age at cool temperatures, naturally present bacteria convert that urea into ammonia and break down another compound in the flesh into trimethylamine, which has a strong fishy odor.
This chemical transformation is what makes fermented skate so distinctive. The ammonia raises the pH of the flesh to somewhere between 8.6 and 9.4, making it strongly alkaline. For reference, fresh fish is close to neutral (around pH 7), while household ammonia cleaner sits around pH 11. That high pH environment essentially acts as its own preservative, inhibiting the growth of harmful bacteria without any need for salt curing or cooking. The ammonia nitrogen content in commercially fermented skate ranges from roughly 5 to 7 grams per kilogram of fish, enough to produce a sharp, eye-watering smell.
The primary species used is the mottled skate, found in the waters off southern Korea, southern Japan, and the East China Sea. Fermentation typically happens in clay pots or containers stored in cool environments, and the process can take anywhere from several days to a few weeks depending on the desired intensity.
What It Tastes and Smells Like
The first thing anyone notices about fermented skate is the smell. The ammonia hit is immediate and intense, similar to a concentrated cleaning product. First-time eaters often describe an involuntary physical recoil. The ammonia doesn’t just register as an odor; it creates a stinging, tingling sensation in the nose and the back of the throat, almost like breathing in something spicy.
The texture is firm and slightly chewy, characteristic of cartilaginous fish. Because skate has no hard bones, only soft cartilage, the entire piece can be eaten. The flavor underneath the ammonia is mildly sweet and fishy, though most newcomers find it difficult to perceive anything beyond the pungency. Devoted fans describe a complex, almost addictive quality that develops as your palate adjusts over repeated tastings. Few people in Seoul have a taste for it, but those in southern Korea who grew up eating it tend to be fiercely loyal to the dish.
How Fermented Skate Is Served
Fermented skate is almost always eaten raw. It arrives at the table as small, thin slabs cut sashimi-style, with no cooking or further preparation. The most iconic way to eat it is in a combination called hongeo samhap, a trio of fermented skate, well-aged kimchi, and steamed pork belly (bossam). The three components are stacked together and eaten in a single bite. The fatty richness of the pork and the sour tang of the kimchi help balance the ammonia punch of the skate, and the combination is considered far more approachable than eating the fish alone.
This trio is a staple at weddings, holidays, and family gatherings in the Jeolla region. It is also available at specialty restaurants in Korean cities, though it remains a regional taste that many Koreans from other provinces have never tried or actively avoid.
Nutritional Profile
Fermented skate is a high-protein, very low-fat food. Analysis of fermented skate skin (one of the commonly eaten parts, since cartilaginous fish have edible skin) shows roughly 22% protein and under 1% fat, with about 74% water content. The dominant minerals are potassium and phosphorus, though fermentation reduces their concentrations compared to fresh skate. Because skate is a cartilaginous fish, its tissue contains chondroitin sulfate, a compound widely sold as a joint health supplement. Chondroitin sulfate from skate cartilage has demonstrated anti-inflammatory properties in research, along with potential benefits for cholesterol metabolism and antioxidant activity, though eating fermented skate is not the same as taking a concentrated supplement.
Comparisons to Other Fermented Fish
Fermented skate occupies a unique niche among the world’s fermented fish traditions. Swedish surströmming (fermented herring) is probably the closest comparison in terms of sheer smell intensity, but the two products work through different chemistry. Surströmming ferments in brine and produces its odor primarily through bacterial action on proteins, generating hydrogen sulfide and other sulfur compounds. Fermented skate’s smell comes from ammonia and trimethylamine, giving it a sharper, more chemical character rather than the rotten-egg quality of surströmming.
Icelandic hákarl (fermented shark) is a closer relative in terms of process. Greenland shark also stores urea in its flesh, and the fermentation similarly converts it to ammonia. Both foods are cartilaginous fish preserved through alkaline fermentation. The key difference is preparation: hákarl is typically hung and dried for months, while fermented skate is aged in a sealed, cool environment and eaten soft and moist. Japanese kusaya (dried, fermented fish) and various Southeast Asian fish pastes round out the global family of powerfully pungent fish products, but none share the specific urea-to-ammonia pathway that defines skate and shark fermentation.
Why It Matters in Korean Food Culture
Fermented skate is more than a curiosity. In the Jeolla region, it functions as a cultural identity marker. Offering hongeo at a family event signals tradition, generosity, and regional pride. The dish’s extreme flavor also makes it a kind of social test. Sharing fermented skate with someone and watching their reaction is a bonding ritual, and developing a taste for it is sometimes described as a rite of passage.
The mottled skate population in Korean waters has declined in recent decades, pushing prices up significantly. High-quality fermented skate can be expensive, reinforcing its status as a special-occasion food rather than everyday eating. Imported skate from other regions is sometimes used as a substitute, though purists insist on locally caught fish for the best results.