Recipes

Shio Koji

If you want to understand what koji actually does, make this tomorrow — it takes three ingredients, a week, and no equipment. Koji is not a flavor, it is an enzyme factory: amylases that cut starch into sugar and proteases that cut protein into amino acids. Shio koji puts those enzymes in a jar and lets you use them like salt.

Fermented · Japanese · Condiment · Sauces

Shio Koji
Prep 10 minutes
Cook 1 week
Serves Makes about 400 g
Level Easy

If you want to understand what koji actually does, make this tomorrow — it takes three ingredients, a week, and no equipment. Koji is not a flavor, it is an enzyme factory: amylases that cut starch into sugar and proteases that cut protein into amino acids. Shio koji puts those enzymes in a jar and lets you use them like salt.

Ingredients

  • 200 g rice koji
  • 60 g salt
  • 200 ml water

Directions

  1. Key ingredients
  2. Rice koji, salt, water — roughly 1 : 0.3 : 1 by weight.
  3. Break up the koji if it is caked, then combine everything in a jar and stir.
  4. Leave at room temperature about a week, stirring daily. It will soften, loosen, smell sweet and faintly boozy, and the grains will start to break down.
  5. It is ready when the mixture is loose and creamy and a grain crushes easily between your fingers.
  6. Refrigerate. It keeps for months and slowly keeps improving.
  7. Use it like salt, at about 10% of the weight of the food: on chicken, pork, fish or vegetables, from an hour to overnight. Wipe off the excess before high-heat cooking — the sugars will brown fast.

Notes

PROVENANCE. Mine, and the best entry point into the koji family I know.

WHAT IT IS DOING: the proteases tenderize by actually cutting protein — this is not the surface-only effect of an acid marinade — while the amylases add a subtle sweetness and the released glutamate does what glutamate does. It seasons, tenderizes and adds savory depth in one step.

IT WILL OVER-TENDERIZE if you leave delicate fish in it overnight. Start with an hour on fish, longer on chicken and pork.

THE FAMILY THIS BELONGS TO: koji (Aspergillus oryzae grown on grain) plus one more decision gives you amazake, sake, mirin, rice vinegar, Miso, Homemade and soy sauce. Once you see koji as a set of scissors rather than a flavor, a dozen apparently unrelated ingredients turn out to be one trick.

BUY SPORES, NEVER WILD-CATCH A MOLD if you go on to grow your own koji. You cannot tell A. oryzae from something harmful by looking, and some Aspergillus species produce aflatoxins. A. oryzae is domesticated and safe; its wild relatives are not all safe. This is the one place in fermenting where ‘use a purchased culture’ is a safety instruction rather than a convenience.

Japan named A. oryzae its national fungus in 2006, which tells you how central this is.