Why It Works
- Allowing the mixture of rice koji, water, and salt to ferment at room temperature tempers the salinity of shio koji and produces its characteristic fruity, sweet, and funky aroma.
- Shio koji is a simple and versatile cure/marinade for poultry, meat, seafood, and even vegetables that imparts savory and subtle sweet notes to foods, while also tenderizing them thanks to enzymes that break down both proteins and starches.
- As with other koji-derived products, such as soy sauce and miso, shio koji will keep for a long time when refrigerated, making it a great addition to your arsenal of flavor-boosting ingredients for sprucing up your everyday cooking.
Shio koji is a Japanese cure/marinade made by fermenting grain koji (cooked grain, traditionally rice, that has been inoculated with Aspergillus oryzae, the mold that gives us miso, soy sauce, and sake), water, and salt until the mixture thickens to a porridge-like consistency and takes on a sweet, funky aroma.
Rich in protease and amylase enzymes that can break down proteins and starches, respectively, shio koji can be used as a marinade for meats, fish, and vegetables. It imparts savory and subtle sweet notes to foods while also tenderizing them. Along with its use as a versatile, flavor-boosting marinade, shio koji can be blended and added to sauces to provide them with an extra umami boost.
- 1 2/3 cups (300g) firm granular rice koji (see note)
- 7 tablespoons (75g) Diamond Crystal kosher salt
- 1 2/3 cups (400g; 400ml) water
In a lidded container, combine koji and salt, breaking up any clumps of koji either with clean hands or a spoon. Add water and stir until mixture is well-combined and salt is dissolved, about 30 seconds.
Cover container with lid and set aside to ferment at room temperature until koji mixture is thickened and smells sweet and funky, at least 7 days or up to 10; stir mixture once per day throughout this fermentation process. Once shio koji is fermented, transfer to refrigerator until ready to use. Shio koji can be refrigerated in an airtight container for up to 10 months.
Rice koji can be found in some well-stocked supermarkets as well as Japanese markets or online. Our favorite brand is Cold Mountain, which can be purchased online here. Prepared shio koji is also available for purchase, but it is often overly sweet and treated with alcohol to lengthen its shelf-life.
Make-Ahead and Storage
Once fermented, shio koji can be refrigerated in an airtight container for up to 10 months.