How to Make One Year Fermented Miso

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We make miso by mixing soybeans, or other legumes, with the fungus Aspergillus oryzae and salt, and allowing fermentation to occur. Usually, miso ferments for six months to a year. It can also be made with rice, wheat, and oats incorporated. Miso contains a lot of beneficial vitamins, minerals, proteins, fiber, and isoflavones. Come learn how to make miso with us!

The History of Miso

Different regions of Japan, China, and Korea all make different types of Miso, incorporating various local ingredients like barley, brown rice, adzuki beans, mung beans, and even hemp. Miso as we know it originates from Japan. Some scholars think that China or Korea introduced miso to Japan around 600 AD. A lot of cuisines are flavored with miso, the most popular and well known is Japanese miso soup. 

Miso as we know it originated anywhere from 10,000 to 5,000 years ago. Scientists think that miso was made from fermented grains, shellfish, fish, and meat preserved in salty seawater, later, evolving into a product made with beans.

How is Miso Made?

Miso is made with koji. Koji is the common term, but the taxonomic name is Aspergillus oryzae, a fungus. The important factors that contribute to miso quality and flavor are fermentation temperature, fermentation time, total salt concentration, Koji quality and variety, and substrate used (type of grain or legume used). You can find koji online, or at an Asian market. You can really manipulate the flavor of miso by adjusting the ratio of koji used. More koji means sweeter miso, less koji means more savory miso.

I’m not going to dive into miso mathematics rationale too much, because it’s a bit more complicated than measuring salt for fermented vegetables. Just know that I make my miso with the intent that the final total salt concentration of the mixture is usually between 12%-17%. This is what I like to do: I cook a bunch of lentils, then weigh the cooked lentils with the koji (in grams), multiply that weight by 0.17 and add the result in grams of salt.

Miso can be made using any type of legume and/or grain. My favorite kind is lentil miso, and I’m currently experimenting with a sprouted lentil, buckwheat, and oat miso. Lentil miso just comes out with a silky-smooth- like texture that’s a little bit different from soybean miso. I like to blend my miso into a smooth paste after fermenting using my blender, but you can also leave it as is for miso with more texture. 

Making miso is pretty simple, the most important step is… you guessed it… weighing your ingredients! Here are the ingredients and supplies you’ll need:

• Large glass Jar
• Plastic Wrap
• Sea Salt
• Lentils (or any legume)
• Koji (Aspergillus orzaye)
• Cheap Vodka (for cleaning)
• Kitchen Scale
• Large Bowl
• Potato Masher

The Timeline

Preparing the miso will take two days, and the fermentation time is 365 days. You can taste test and eat the miso anywhere between the 6 months and 1 year mark, though.

To start the process, you’ll need to soak the lentils for 12 hours. After soaking you cook the lentils until they are soft enough to mash with a fork or potato masher. Allow the lentils to cool to room temperature, then mix in the koji and salt. Last, you pack the miso into the jar, cover it with salt and plastic wrap, and put it away to check after three months.

When checking the miso, you want to look for signs of surface mold. If blue, black, or green mold grows on the miso mixture, it’s no longer safe to eat and should be discarded. If you follow all the directions, clean your equipment properly, and weigh the ingredients this should not be an issue. If everything looks fine, remove the plastic wrap and turn/stir the miso with a clean spatula. Smooth and pack the miso back in and place a clean piece of plastic wrap to tuck the miso in. Last, you’ll allow it to ferment for 3 to 9 more months. I like my miso fermented for a year the best. I pulled the miso pictured here at 8 months, and it was delicious.

The Microbes in Fermented Miso

Koji is the starter culture we use in miso fermentation. It is rice with spores from Aspergillus orzaye fungus. This is the starter, however, the total desirable microbial composition usually includes:

• Aspergillus oryzae 
• Tetragenococcus halophila
• Enterococcus faecium
• Lactococcus spp.
• Lactobacillus spp.
• Pediococcus spp.

Bacillus spp. are sometimes found in miso, but their growth is inhibited by bacterocins produced by Enterococcus faecium. Bacillus spp. are halotolerant to light halophiles, so they love to grow on media with about 15% to 20% (w/w) NaCl. Bacillus species often reside on rice, so their presence makes a lot of sense, but is not ideal.

The rate at which Aspergillus oryzae grows is largely determined by the temperature of fermentation. Aspergillus oryzae can tolerate extreme conditions, like high salt concentration, if all of the other conditions are ideal. Ideal fermentation temperature is cooler, around 70 Degrees F. Some say that the best miso is started in the winter, in order to cycle through cold winter temperatures, then slightly warm spring temperatures, then to finish off in warmer summer temperatures. This probably compliments and promotes the different phases of fermentation that occur in miso.

Since Aspergillus spp. are fungi they are dependent on decomposing their surroundings for nutrition. To rely on surrounding substances for nutrients, they release different types of enzymes such as amylase. These enzymes are capable of breaking down organic matter into simpler compounds as a food source that the fungi can absorb through hyphae. This is what the fungus does to beans in miso fermentation, creating fermentation byproducts beneficial for digestive health.

The Health Benefits of Fermented Miso

Some research has shown that miso can aid in the prevention of radiation injury, liver cancer, breast cancer, and intestinal tumors in animal models.

This study was conducted to understand why the citizens of Okinawa Japan have such a long life expectancy. In this area of Japan, miso soup is a major staple of the average diet. Miso is full of antioxidants that may help reduce oxidative stress and thus the risk of cardiovascular disease, cancer, and some chronic diseases. So the long life expectancy makes sense!

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References: 

Frias, Juana & Martinez-Villaluenga, Cristina & Peñas, Elena. (2016). Fermented Foods in Health and Disease Prevention.