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How To Use Moromi - The Mash From Making Soy Sauce
- Ernest Foundas
- Aug 7
- 4 min read
The first blog entry on our Tiki Food Lab research blog was an explanation of how to make soy sauce. Now that the soy sauce we made for that blog has been fermenting for two years, we wanted to do a follow-up regarding what to do once your soy sauce is ready to come out of ferment.
People regularly ask how long to ferment soy sauce (shoyu), and the answer is – well, it depends. When you put together your initial soy sauce fermentation mixture, you should think about how long you WANT to ferment it. Longer ferments should have somewhat higher salt content. In general, we are comfortable using 8-10% salt for a long-term ferment (ie: several years or more). Soy sauce is slow food after all! However, if you want to enjoy soy sauce sooner, you can get away with lower salt content, even down to 3%. This is a good way to make low sodium soy sauce, but the shorter fermentation time does tend to yield a less complex flavor. As with many cooking techniques, the recipe changes based upon your goals, time, and equipment on hand.
Once your soy sauce has fermented to a point where you are ready to “rack” it, then you are about to have a range of fabulous ingredients at your disposal – such as Moromi and thick soy sauce!
Moromi is what is left after you strain the solids out of your soy sauce. If you are more familiar with other forms of fermented beverages, it is essentially the equivalent of mash, lees, must or pomace – which are all names for the strainings you get after making various fermented beverages like soy sauce, wine, sake and liquor.
When you strain your fermented soy sauce, the first step is to strain through a rough shinwa. The initial straining is Moromi, but it can then be pressed in cheesecloth to remove additional liquids and to make your Moromi thicker and drier.
Next, you can strain your liquid soy sauce through cheesecloth again to remove additional solids, and finally, if you want your soy sauce to be clear and free of debris, you can freeze it and then thaw in cheesecloth.[1] When you freeze a liquid with suspended particles and later thaw, the process of melting occurs first with the liquid, causing the solids to be left behind – thus clarifying the solution.
When performing your straining, the mostly solid residual from the first straining is Moromi. The thick liquid you get from your second straining is what we call Thick Soy Sauce, and then the final product is Soy Sauce! So much complexity from one ferment.
What Is Thick Soy Sauce & Variations
Thick Soy Sauce is a term with wide application. Some people refer to Tamari as thick soy sauce, because it has a higher concentration of soybeans. In commercial settings, Thick Soy Sauce is a product where sweeteners and starch are added to soy sauce and brewed, reduced, or further fermented to make a sweet syrupy soy sauce. However, we refer to Thick Soy Sauce as the heavy strainings that you get from your second straining. The flavor is complex, with a heavy soy/wheat umami-rich essence!
When we have Thick Soy Sauce, we don’t typically add sweeteners or additional thickening agents, because those can be added when you prepare it for use in a given recipe. In other words, if you want to make a hoisin-type sauce, you take your unadulterated Thick Soy Sauce and simmer with brown sugar, molasses, honey, and any other spices you want to use. You can also add cornstarch or potato starch or arrow root to make it thicker.
How To Use Moromi
Once you have diligently strained your soy sauce, you need to decide what to do with your Moromi! Some fermenters use some Moromi to backslop their next batch of soy sauce. However, we prefer to use all of our precious Moromi, because it is such an amazing umami packed powerhouse of flavor. You can use it as you would miso or other flavor pastes in a wide array of dishes to add flavor and umami.
You can also make what we call Seasoned Moromi, which is when you add other flavors to Moromi and use it right away or continue to ferment to create a double fermented sauce. At Suis Generis, we recently did a chili Moromi sauce with buffalo milk burrata and clove bruleed peach. So tasty!
An important consideration in making Seasoned Moromis for a second ferment is your salt content. For example, if you started with a soy sauce with 10% salt, your Moromi should also have 10% salt. So if you add equal weight of another flavoring agent to make Seasoned Moromi, such as chili flakes or seaweed, the resulting salt concentration would be 5%, which should still be fine for a secondary ferment, especially considering the presence of koji in the mixture. As with all ferments, you should always track your original salt and koji content in case you later want to transition into a secondary ferment to make sure you maintain safe levels of salt and koji to ward off bad bacteria.
Here are some Seasoned Moromis we recently put together from our soy sauce mash:
Safety is always a key factor in any ferment you do – and if you follow a plan for how to make your fermented goodies, the odds of something going wrong are significantly decreased. Our suggestion is to always weight your ingredients, track your percentages of salt and koji, and keep oxygen off the surface by using a raft (often saran wrap) and by checking and stirring the ferment occasionally. Then, trust your nose, because if something goes wrong, it will let you know.
[1] To our knowledge, this technique was fist devised by Noma, which refers to it as “Ice Clarification.” See, https://www.instagram.com/p/C7Eg2NAoFbz/?hl=en&img_index=1.