Key findings
- 1Traditional miso is one of the oldest fermented foods, dating back over 1,300 years in Japan
- 2In our analysis, miso products average a Processing Score of 5.3, which is Level 3
- 3The color difference between white, yellow, and red miso comes from fermentation time, not added ingredients
- 4Instant miso soup packets are a different product, typically with dried additives and preservatives
Why is Miso Level 3 on average?
Miso production relies on a double fermentation. First, koji mold is cultivated on rice or barley for 2-3 days, producing enzymes (proteases, amylases) that break down proteins and starches. The koji is then mixed with cooked soybeans and salt, packed into vessels, and fermented for 3 months to 3 years depending on the variety. During this extended fermentation, enzymatic reactions produce hundreds of flavor compounds, glutamate (natural umami), and beneficial microorganisms. White (shiro) miso ferments for weeks, while red (aka) miso ferments for over a year. The fermentation time, not any additive; creates the color and flavor differences between varieties. In our analysis, miso products average a Processing Score of 5.3, which is Level 3.
How 167 miso products break down
Share of products at each processing level, in our analysis.
Miso brand comparison
From least to most processed in our database.
How to read a miso label
- 1
Traditional miso lists: soybeans, rice (or barley), salt, water, koji culture
- 2
Watch for miso with added MSG, alcohol (ethanol preservative), or bleaching agents
- 3
Unpasteurized miso retains live cultures, look for "live" or "unpasteurized" on the label
- 4
Instant miso soup packets with dried toppings and flavor enhancers are more processed
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Frequently asked questions
Is miso paste the same as miso soup?
Miso paste is the fermented ingredient. Instant miso soup packets that include dried tofu, seaweed, MSG, and preservatives are more processed. Miso soup made at home from paste, water, and fresh ingredients stays simple.
Does miso contain MSG?
Traditional miso naturally produces glutamate through fermentation; the same compound in MSG but formed through biological processes rather than industrial synthesis. Some commercial miso adds manufactured MSG as a separate ingredient. Check the label.
Is white miso less processed than red miso?
No. White (shiro) miso ferments for a shorter period (weeks to months) while red (aka) miso ferments for 1-3 years. The longer fermentation in red miso is actually more traditional, not more processed.