• Home
  • HOW TO
  • Understanding Fermentation Basics through Miso and Soy Sauce


Jan 10, 2023

HOW TOUnderstanding Fermentation Basics through Miso and Soy Sauce

Miso and soy sauce are widely used in Japanese cuisine, but their production methods aren’t well known. Let’s dig into how they’re made, explore the health benefits of fermented food and introduce the powerful fungus koji.

Jan 10, 2023

Making miso

With such a profound flavor profile, you might be surprised to learn that miso paste is made with just a few ingredients, soya beans, salt, koji or koji rice, fungus, and other additions like barley, or millet. The intense umami flavor comes from the fermentation process. So, how is it made?

The magic of miso is the transformation the soya bean makes when it is fermented. To achieve this, dried soybeans are first soaked in water, and the plump beans are then steamed or boiled.

After cooking, the beans are mashed and minced, and a koji-infused addition, usually koji rice or koji barley, is added, along with salt and water. The mixture is blended and left to ferment for a year or more in wooden vats before it’s ready to eat.

The secrets of soy sauce

Soy sauce typically contains five ingredients: soybeans, koji, wheat, water and salt, although as with every artisan product, some producers tweak the recipe to suit the desired taste. Again, fermentation is the key to the accompaniment’s unique flavor.

To make soy sauce, soybeans are first steamed. Next, the cooked beans are mixed with koji and crushed wheat, and the mixture is left to ferment for a few days. Next, salt and water are added to the mash, which is mixed regularly for up to three years before the final product is ready. Natural, airborne yeast helps with fermentation.

At the end of the fermentation process, the solid mash is passed through cloth to extract the liquid. Finally, the soy sauce is heated slowly, and all the impurities are skimmed from the top of the vat.

What is koji?

We’ve mentioned koji several times in this article, but what exactly is it? In its purest state, koji is an edible fungus called Aspergillus oryzae. While some molds and fungi release toxic enzymes whilst breaking down ingredients, koji does not.

Instead, it releases a series of friendly amino acids, good for health, and in the case of glutamate, the catalyst for umami flavor, delicious too. Koji fungus is generally cultivated on soybeans, that provide the koji with nutrition to grow, and that can be easily placed in the perfect environment for koji growth. The koji spores by themselves might be difficult to work with, harvest, measure and store. So, they are usually processed with rice or barley. This production process is in itself a fine art, and koji rice and koji barley producers are trained craftspeople.

Beyond miso and soy sauce, you’ll find koji in a wide variety of other Japanese staples, like mirin and some sakes.

How healthy are fermented foods?

As well as being delicious, fermented foods like miso and soy sauce have many different health benefits, most of which revolve around the gut. Primarily, fermented foods help to rebalance the bacteria in the stomach, which is often stripped by unhealthy, high-sugar foods, strengthening your immune defense.

These bacterias also help to detoxify your body by drawing out heavy metals and other unwanted toxins. Fermented foods also contain nutrients, particularly vitamin K and essential B vitamins. Along with the mood-boosting effects of B vitamins, bacteria found in fermented food can also increase serotonin production, making you feel happier.