The Japanese ingredient koji is the fungus that grows on rice, barley, soybeans, or corn after it is inoculated with a fermentation culture called Aspergillus oryzae. It resembles thin rice porridge and is full of enzymes that produce amino acids when they interact with protein. One of those amino acids, glutamate, is responsible for the taste we know as umami, which is present in miso and soy sauce and makes foods especially savory and flavorful. There are two types used for cooking: Ama-koji and Shio-koji. Ama-koji, called for here, has no salt, so you can control the seasoning yourself. In this simple recipe, it’s added to salmon fillets before they hit the grill, which lightly cures them and adds an umami kick.
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- 2 (4-oz.) salmon fillets
- Salt, to taste
- 2 tbsp. Ama-koji (available at Asian grocery stores)
- Plastic wrap
- Season the salmon fillets with salt. Let them rest for 20 minutes in the fridge.
- Dry the fillets and wrap them in one layer of cheesecloth. Evenly spread the Ama-koji on the wrapped salmon then wrap again using the plastic wrap. Let the salmon marinate overnight.
- Remove the plastic wrap and cheesecloth from the salmon and grill to your preferred doneness. (Due to the enzymes found in the Koji you’ll notice that the salmon is extremely tender and buttery. Because of this the author recommends grilling to rare or medium-rare.)