Shio koji

Shio koji contains proteolytic enzymes produced by the Aspergillus oryzae mold that break down proteins into amino acids. When used as a marinade, these enzymes naturally tenderize meat and fish while infusing them with a deep, savory umami flavor.

You can easily make shio koji at home by mixing rice koji, salt, and water, then letting it ferment at room temperature for about a week. However, it is also widely available commercially in jars at Japanese supermarkets if you prefer the convenience.

A general rule of thumb is to use about one and a half to two times the volume of shio koji for the amount of regular salt required in a recipe. Because it is a wet paste, you might need to slightly reduce other liquids in the dish to maintain the proper consistency.

Store-bought or homemade shio koji will keep for several months in the refrigerator, often up to six months if kept tightly sealed. You will know it is past its prime if the aroma turns overwhelmingly pungent or if the texture breaks down entirely.