Best koji rice substitutes | Other things to ferment with koji

by Joost Nusselder | Updated:  June 5, 2022

17 easy recipes anyone can make...

All the tips you'll need to get started in Japanese cooking with, FOR A LIMITED TIME, FREE as our first email: the complete Japanese with ease cookbook.

We'll only use your email address for our newsletter and respect your privacy

I love creating free content full of tips for my readers, you. I don't accept paid sponsorships, my opinion is my own, but if you find my recommendations helpful and you end up buying something you like through one of my links, I could earn a commission at no extra cost to you. Learn more

Ever had trouble finding Japanese recipes that were easy to make?

We now have "cooking Japanese with ease", our full recipe book and video course with step-by-step tutorials on your favorite recipes.

Rice koji is the most popular kind of koji.

But there is good news for anyone who wants to enjoy the unique umami flavor of koji fermented foods but is looking for alternatives to rice koji.

Best koji rice substitutes | Other things to ferment with koji

The joy of koji is that the koji starter or koji-kin can be used on a variety of grains and legumes and even on vegetables, in fact on any food rich in carbohydrates. So, you are certainly not limited to using rice. Two of the most common alternatives to koji rice are barley koji and soybean koji.

In this post, I’ll explain what other foods can be combined with koji for amazing umami flavor and how to go about it.

What is koji and what is koji rice?

If you know even a little about Japanese cuisine, you will be familiar with ingredients like soy sauce, miso, mirin, amazake (a non-alcoholic sweet rice drink), and rice wine vinegar.

What you may not know, however, is that these are all koji-fermented foods.

Koji has been used in Asian countries for centuries in the making of soy sauce, miso, douche, and alcoholic drinks but the first step required to make any of these products is creating the koji-kin or starter.

The short answer is that koji (also known as rice malt) is an edible fungus called Aspergillus oryzae.

Much like the yeast in breadmaking, the koji kickstarts the fermentation process when added to ingredients like rice, barley, beans, or legumes.

For koji rice, the koji starter or koji-kin is propagated on steamed rice. It is also called shio koji, which means ‘salty koji rice’.

Koji rice is probably the most popular kind of koji but there are many other grains and legumes that can be successfully used as substitutes for koji rice.

What is koji-kin?

Koji-kin is the ‘starter’ that is used to create fermented food. To make the starter, koji mold, aspergillus oryzae, is added to steamed rice or cooked legumes.

The resulting mixture is then placed on wooden trays, in a warm and humid place for up to 50 hours.

During this time the koji mold feeds on the carbohydrates and proteins and converts them into sugars and amino acids.

This is then used as the starter (the ingredient that kickstarts the fermentation process) for making products like mirin, soy sauce, miso, and sake.

Wondering what kind of miso to use for soup? I explain the options here

Substitutes for koji rice

If you are looking for substitutes for koji rice, here are some suggestions.

Barley koji

Barley koji is used as the starter for making barley miso, kinzanji miso, and shoyu.

Miso is a thick aromatic paste that is used to flavor soups, sauces, and other savory dishes. “Mugi miso” is miso made with barley koji.

It takes longer to ferment than miso made with rice koji and it has a lighter taste and is slightly sweeter.

Products made with barley koji have a unique fragrant aroma that comes from the barley.

Soybean koji

Soybean koji is made by inoculating steamed soybeans with koji spores.

Soybean koji is mainly used to make soybean miso, which comes in different varieties and colours.

The soybeans need to be soaked for at least 12 hours, drained, and then steamed, either in a normal steamer or in a pressure cooker, before adding the koji-kin to start the fermentation process.

Quinoa koji

Quinoa koji can be made by soaking quinoa in water, allowing it to germinate, and then adding salt and koji and allowing it to ferment slowly.

The resulting paste is very smooth which makes it easy to mix with dressing for salads or seasonings for stir-frying.

Quinoa koji offers a gluten-free alternative to rice koji.

Here is a review of the best rice cookers reviewed to cook white rice, brown, sushi and even quinoa

Shio koji

Shio koji or koji salt is made by combining cooked grain with koji, water, and salt and allowing the mixture to ferment for a couple of weeks at room temperature to become a thick salty paste with a light miso flavor.

This can be used as an alternative to salt. It can also be used to marinate meat and fish, pickle vegetables, or as a substitute for soy sauce.

Shio koji can also be blended and added to sauces and dressings to give them the iconic umami taste. It’s also the signature flavor of a whole range of Japanese ramen recipes.

Lentil koji

Red lentil miso is easy and quick to make. You don’t need to soak the lentils overnight and they cook in less than half an hour.

Mix the cooled lentils with koji and salt, form into palm sized balls and press them into a jar. Leave to ferment for about four months or less if the ambient temperature is warm.

The resulting red lentil miso is delicate sweet miso that is perfect for salad dressings and soups.

Green lentil miso, which can be made in the same way, adds a delicious earthy umami flavor to soups and stews and goes especially well with dishes containing coconut milk.

Split pea koji

A delicious split green pea miso can be made by combining cooked, cooled split green peas with salt and koji-kin and leaving it to ferment for about four months.

The resulting sweet paste can be used in marinades and sauces and even with fresh vegetables.

Vegetable koji

The taste of most vegetables is enhanced by the addition of koji but it is especially noticeable with bitter vegetables.

Broccoli, different cabbages, radish, carrots, or other root crops become significantly sweeter and more umami with the addition of koji.

Vegetables develop this sweet taste because koji releases the enzyme amylase which converts the vegetable starches into sugar.

The koji also releases other enzymes which break down the proteins to create amino acids which carry the unique umami flavor.

Learn about the basics of using koji with vegetables here:

What else is koji used for?

  • For making alcoholic drinks like sake and shochu (a distilled liquor). It is also the main ingredient in the sweet drink, amazake.
  • For making condiments. Rice vinegar and mirin, which is a sweet cooking wine, are both the result of the fermentation process from koji.
  • For making miso. Cooked soya beans (or other legumes) are combined with koji and left to ferment. The result is a paste which can be used as a pickling agent or a base for marinades and dishes like miso soup.
  • Shio koji or koji salt is made by combining koji rice with salt and water and leaving it to ferment.
  • For making shoyu, which is a Japanese-style soy sauce. Shoyu is made using the same technique for making miso. Cooked soya beans and salt are combined with koji and left to ferment. The resulting paste is then pressed and filtered to produce the soy sauce.

What are the health benefits of koji?

Recently there has been a lot of buzz about fermented foods and there is a renewed interest in koji and other fermented foods like kombucha, kimchi and kefir.

Although fermentation is one of the oldest culinary practices, it has recently become increasingly popular because of the numerous health benefits that it offers.

Gut health

Fermentation is a great source of probiotics (beneficial bacteria) which promote gut health and also increase the absorption of nutrients into the body.

A healthy gut leads to a strong immune system.

Weight management

Research shows that koji can help reduce body weight and lower blood glucose levels.

Fighting fatigue

Koji is rich in Vitamins B1, B2 and B6. The digestive enzymes in koji break down carbohydrates and convert them into energy.

How to make your own koji

If you are keen to make your own koji, here are some pointers to guide you. I explain the full recipe for koji rice here.

The most difficult part of making homemade koji is finding the koji spores (koji-kin). You may be able to find koji-kin in your local Japanese grocery store or you can buy it online.

Make sure that it’s koji-kin, not koji rice.

It is important to buy koji spores from trusted or reputable suppliers. Inferior quality spores often contain other unwanted mold strains which can interfere with the fermentation process.

Make sure to use quality ingredients. It’s best to use polished rice and pearl barley as it’s easier for the koji to get to the food source.

All equipment, utensils, and your hands must be cleaned and sterilized. Mold fermentation happens at high humidity, which is also the ideal environment for bacteria to multiply.

It is important not to under- or overcook your basic ingredient.

If it is undercooked the koji will struggle to grow, and if it is overcooked the koji will be unable to produce the necessary enzymes.

Never let the temperature of the koji go above 40 degrees Celsius or 104 degrees Fahrenheit. The mold will die above this temperature. It grows best at around 30 degrees Celsius or 86 degrees Fahrenheit.

It grows best on breathable wooden trays.

For best results, mature the koji in the fridge for 2 – 3 days before using or storing.

Takeaway

As I have shown in this article, one of the joys of cooking with koji is its versatility.

Although koji rice is probably the most popular type of koji, the koji-kin can be used on a variety of grains and legumes as well as on vegetables. So, you are certainly not limited to making koji rice.

Did you know they also have a fermented soybean paste in Korea, called Doenjang?

Ever had trouble finding Japanese recipes that were easy to make?

We now have "cooking Japanese with ease", our full recipe book and video course with step-by-step tutorials on your favorite recipes.

Joost Nusselder, the founder of Bite My Bun is a content marketer, dad and loves trying out new food with Japanese food at the heart of his passion, and together with his team he's been creating in-depth blog articles since 2016 to help loyal readers with recipes and cooking tips.