Koji is defined as steamed rice, wheat, soybeans, or other grains on which koji bacteria are propagated. Koji is used in a variety of fermented foods that have surrounded Japanese food culture since ancient times, including sake, miso, vinegar, pickles, soy sauce, and shochu. Kojizuke is made by mixing koji with salt and sugar and pickling vegetables, poultry, fish, and shellfish in the mixture. By marinating meat and fish in salted koji, the proteins are broken down into amino acids, which increases their umami, making them tender and moist. Of course, it also has the advantage of enhancing the preservation of foodstuffs.