Frequently asked questions about Koji

What is Koji?

Koji is the term for a grain or bean that has been inoculated with Aspergillus Oryzae, a special fungus that has been domesticated for about 9000 years. 
White Rice Koji is made by steaming white rice and then allowing spores of Aspergillus Oryzae to germinate and multiply on it. 
This process is carefully controlled to ensure conditions are perfect for koji growth, with both temperature and humidity monitored continually. The fungus then converts starch within the rice into a range of enzymes, which go on to create the delicious range of savoury/umami flavours within foods like miso and soy sauce.

Can you eat Koji?

Koji can be eaten raw, but is at it’s best when added to other ingredients to create an umami flavour in the food.

Does Koji contain any allergens?

Koji does not contain any of the 14 allergens named by the UK food standards agency, and can be used to make allergen free alternatives of popular Japanese foods such as miso (e.g. using fava beans or green lentils), or soya sauce (using fava beans)

Is Koji vegan?

Yes, Koji just contains rice and a fungus and is completely vegan.

If you have any more questions about Koji, or how it is used, please leave a question in the comments and we’ll do our best to answer it.  

8 thoughts on “Frequently asked questions about Koji

  1. Hi,
    Do you make koji yourself, in the UK? Or is it imported?

    1. We make all our koji here in the UK – in rural Worcestershire. It’s all handmade in small batches.

  2. Hi, how long is the shelf life? Where should I keep it before opened and after?

    Many thanks.

    1. The shelf life is four months from manufacture, so will generally be 3+ months from purchase.

      Before opening it can be stored on a shelf/in a cupboard – just as you’d store uncooked rice.

      After opening it is very important that it stays dry. I have stored open koji for many several months here, but there is a danger it will go bad if exposed to moisture. If possible, store in an airtight container.

  3. Hi. I wonder if you sell just the fungus (Aspergillus Oryzae)? If so, what’s the price per, say, 15g?
    Thank you.

    1. Sorry, due to the agreement we have with the Japanese spore producer we are unable to sell spores – only koji rice.

  4. Hi,
    If im making koji water (blending koji and water and sieve it well) is there an easy (or multiply) way to stabelize it? so it would hold in a fridge longer than 5 days?

    1. It will probably be OK in a fridge for a lot longer than 5 days, but I have to remain on the cautious side of things. The easiest way to get it to last longer is to increase the salt content – or you could add some neutral alcohol. You can also freeze it, or even dehydrate it.

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