What Is Ike Jime?
Ever wonder why yellowtail or bluefin sashimi tastes better at a truly authentic sushi bar? You’ve probably brought fish home from a trip and created your own sashimi platter only to discover it didn’t quite taste the same and the texture wasn’t as nice as what you’re accustomed to ordering at your favorite Japanese restaurant. You just harvested the fish yesterday – it doesn’t get any fresher, so what gives? The way a fish is handled once it comes aboard is what truly makes the difference in terms of taste and quality. Welcome to Ike Jime. Follow this simple four-part process and you will enjoy an elevated caliber of fish at home or on the back of your boat.
The finest quality seafood is often associated with sashimi, sushi, and other Japanese raw fish preparations. Ike jime is a traditional Japanese slaughter technique that involves instantaneously euthanizing a fish by inserting a spike into its brain cavity. The fish is then thoroughly bled and undergoes spinal cord destruction (shinkei jime) before getting iced down.
Why Is Ike Jime Important?
Ike jime produces a biochemically superior grade seafood product as the process helps to eliminate stress and the natural consequences of death. When a fish experiences stress, its brain goes to work by flooding the muscles with lactic acid, cortisol, and adrenaline. Core body temperature also rises. The combination of hormones and elevated temperature turns muscle tissue to mush and negatively impacts taste. When performed correctly, ike jime prevents this from occurring.
The following four steps will yield tremendous results. When performed correctly, you will notice not only a better tasting fish but a fish that will last longer. The term “fresh” is commonly used by grocery stores to convince you to buy their imported fish. A properly processed fish will stay “fresh” significantly longer. Harvested with the ike jime method, fish can be refrigerated for weeks when safely stored in a vacuum sealed bag or airtight container. This process not only makes the fish taste better – it also lasts longer, has zero smell, and reduces waste as it won’t spoil nearly as fast, allowing you to respect the fish and the fishery to the maximum ability.
Four steps to ike jime success: Brain Spike, Bleeding, Shinkei Jime, and Cool Down.
Step 1: The Brain Spike
Spike the fish in the brain to euthanize it before it experiences full suffocation. This prevents the brain from sending signals to the rest of the body, excreting cortisol and adrenaline. Both hormones have detrimental effects on the quality of the meat. The sooner a fish can be spiked, the better its meat will be. When a fish thrashes around on the deck of a boat, it utilizes its last bit of oxygen creating lactic acid in the muscles, a substance that produces more off-flavors. Spiking the brain causes the fish to no longer send these signals and the fish is effectively dead at this point. It can no longer experience stress, allowing you more time to handle the remainder of the process without ruining the meat.
Since every fish is different and the location of their brain differs, there is no perfect way to find the brain. Here are some guidelines that can help. Between the eye and the gill there is a bone structure shaped like the gill called a pre-operculum. Where the pre-operculum and lateral line meet is a good indication of where the brain is. When you spike a fish correctly, its mouth will open, and the body will do a quick flail and the fins will flair. This is a good indication that the spike got the brain, and the fish is dead.
Step 2: Bleeding
Blood is one factor that can lead to fish quickly spoiling. That fishy smell and abbreviated shelf life are often the results of improper (or complete lack of) bleeding. A single spot of coagulated blood on a fillet is all it takes for bacteria to grow.
The best tool for the job is a sharp knife or pair of scissors. To bleed the fish, cut the membrane behind the gills on both sides. The heart is still beating and will pump the blood out. A third cut can be made at the base of the tail fin just barely exposing the large blood vessel located under the spine, or you can make a full cut exposing the whole spine.
Use a hose to help flush out the blood. Blood coagulates quickly, and the pressure of the hose water will stop the blood from clotting and allow it to escape the carcass. Keep the water flowing until it is clear of blood.
If you don’t have a hose, a five-gallon bucket works great as well. Fill the bucket with water and place the fish headfirst into the bucket. While holding the tail, shake the fish. You can also bend the fish, applying pressure to the main artery which will help drive the blood out of the carcass. After a minute or two, change the water out and place the fish back into the bucket headfirst. Continue doing this until you are left with clear water.
This limits the bacterial load within the fish. Blood is very rich and can increase proliferation in bacteria. This process helps extends the shelf life.
Step 3: Shinkei Jime
Many anglers are already well-versed in spiking and bleeding their catch. Performed correctly, these two defensive steps make for a better product in the kitchen. The next step, called shinkei jime, is an offensive step. Shinkei jime refers to the destruction of the spinal cord to delay rigor mortis.
A shinkei jime wire is the most effective and sanitary tool for this step. What this tool does is disconnect any residual signaling that is taking place in the spinal cord to the muscle tissue. This tricks the muscles into not knowing they are dead and delays the time that rigor mortis begins.
The correct wire size is relative to the size of the fish and its length. Using the cut made in the tail, look for the canal above the spine that houses the spinal cord. Run the wire up the neural canal all the way to the brain. Once the wire is completely inserted, pull it back and forth several times to destroy the spinal cord and paralyze the fish. When performed correctly, the fish will occasionally buck wildly and flare its fins. When movement subsides, the fish is now paralyzed and no more neural chemical signaling that exists in the spinal cord can reach the muscle tissue.
Step 4: Cooldown
Blood is one of the main reasons bacteria can get into the meat of a fish, but another factor is heat. It becomes important to bring the core temperature of the fish down as quickly as possible, reducing the bacteria growth in the meat. A 1:1 ratio of ice to water in a slurry that completely submerges the fish is recommended.