To maximise the health benefits of shio-koji and shoyu-koji, we produce them without heat sterilisation or added preservatives. Because these are “live” foods, proper care and hygiene are essential to ensure they remain safe and effective.

1. The Golden Rules of Hygiene

When dealing with live foods that mature at room temperature for several days, hygiene management is your first line of defence against spoilage.When dealing with live foods that mature at room temperature for several days, hygiene management is your first line of defence against spoilage.

Clean Hands, Clean Space: Always work with freshly washed hands in a tidy environment.

Sterilise Your Tools: Only use jars, spoons, and containers that have been boiled or disinfected with alcohol.

The “Clean Spoon” Policy: Always use a clean utensil when taking koji from its storage jar to prevent introducing unwanted bacteria.

Trust Your Senses: If you notice an off-smell, strange taste, or visible mould growth, discard the batch immediately.

2. Salt & Liquid Ratios

Salt acts as the natural stabiliser that protects live foods during the aging process.

Maintain Concentration: As salt concentration decreases, the risk of spoilage increases, so be precise with your measurements

Soy Sauce: When making shoyu-koji, always use standard soy sauce. Avoid low-sodium varieties, as they may not provide enough protection for the live culture during the room-temperature phase.

Managing Dry Koji: All recipes on this site use fresh rice koji. If using commercially available dried rice koji, or rice koji that has lost moisture over time, the standard recipe amounts of water or soy sauce may be insufficient.

In such cases, gradually add additional liquid whilst maintaining the overall salt concentration. Add enough water or soy sauce to ensure that the rice koji is fully submerged and not exposed above the surface.

3. The Cultivation Process

Daily Stirring: Place the storage container at room temperature (ideally between 15°C and 23°C) and stir well once a day using a clean spoon. Repeat this process for approximately 1 to 2 weeks. [Note: the number of days it takes to complete the process will vary slightly depending on the season and ambient temperature, but please use this as a general guideline.]

Aeration: Mixing well is crucial; exposing the live culture to air helps prevent localised bacterial growth.

Environment: Avoid direct sunlight and hot, humid spots. Keep your jars in a stable environment between 15°C and 23°C.

How to Tell it’s Ready: The koji rice should be soft enough to crush easily between your fingertips, and the harshness of the salt should have mellowed. Once it reaches this state, daily stirring is no longer required.

Finishing: For a smoother texture that is easier to use in cooking, you can pulse the finished koji in a blender to remove the grains.

4. Storage & Shelf Life

Refrigeration: Once the initial cultivation is complete, store the jar in the fridge to slow down the biological activity.

Usage Window: For the best flavour and safety, we recommend using your batches within 3 months.