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Soy sauce is one of the most popular condiments in the world, and it’s been used to flavor food for over 2000 years. [1] Making your own soy sauce is a long (and smelly) process, but the final result is a delicious, complex flavor you’ll be proud to serve to your family and friends!

Ingredients

To make 1 gallon (3.8 L) soy sauce

  • 4 cups (950 mL) soybeans
  • 4 cups (950 mL) wheat flour
  • Koji starter
  • 1 gallon (3.8 L) water
  • 3 1 2 cups (830 mL) salt
Part 1
Part 1 of 2:

Making the Soy Sauce Base

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  1. You can get soybeans (or edamame) from some grocery stores, although you may need to visit a store specializing in Asian produce.
    • Make sure you remove the soybeans from their pods before you soak them.
    • If your market makes a distinction between soybeans (mature beans) and edamame (young, softer beans), use the soybeans.
    • To wash the soybeans, place them in a colander and rinse them under cold water. Pick out any beans which seem shriveled or discolored.
  2. Place the soybeans in a large pot, then fill the pot with water until the soybeans are completely covered. This should take about 5 quarts (4.7 L) of water. Drain the soybeans and add fresh water to the pot.
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  3. When they're finished cooking, you should be able to mash the soybeans easily with your fingers.
    • You can also use a pressure cooker to cook the soybeans more quickly if you like. Place the beans in the pressure cooker, add about 1 cup (240 mL) of water and close the lid. Place the pressure cooker over high heat, then reduce the heat when the pressure cooker begins to whistle. Cook the soybeans for about 20 minutes.
  4. Use a food processor, the back of a spoon, or a potato masher to mash the soybeans until they are a smooth consistency.
  5. This should create a dough-like substance. Knead the mixture together until it’s thoroughly blended.
  6. Soy sauce gets its flavor from the microbes Aspergillus oryzae and A. flavus. Traditionally, the fermenting mold was developed by allowing the soybean mixture to sit for a week. However, you can purchase the mold spores, known as koji starter, online or from some specialty health food stores. [2]
    • Read the packaging to determine the amount of koji starter you should add, as it may vary by brand.
    • If your soybeans were still warm when you mixed them with the flour, cool the mixture to about body temperature before you add the starter.
  7. You will leave the koji in the tray while it ferments. Spread the mixture out so it's no more than 2 inches (5.1 cm) deep.
  8. Press down to make long rows through the koji mixture. The furrows should be about 2 inches (5.1 cm) deep and 2–3 inches (5.1–7.6 cm) apart. They should resemble furrows for planting seeds in a garden. [3]
  9. This will allow the cultures to develop. You should see the Aspergillus bacteria growing on the soybean and flour mixture. It should appear light to dark green.
    • After the 2 days have passed, move on to fermenting in a brine mixture.
    • Choose a spot where the koji won't be disturbed as it ferments. The kitchen is ideal if you can handle the smell — try placing the tray in a kitchen cabinet or on top of the refrigerator.
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Part 2
Part 2 of 2:

Fermenting and Pasteurizing the Sauce

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  1. Pour the salt into the water and stir until it's completely mixed together. This salt water brine will help keep unwanted bacteria from growing as you ferment your koji. [4]
    William Shurtleff, Fermented Food Expert

    Traditional soy sauce brewing relies on a delicate fungal culture called koji and Lactobacillus bacteria. Equal parts soybeans and roasted wheat are inoculated and fermented in brine for months, resulting in a complex, salty sauce with savory umami flavor.

  2. Place the koji into a large jar with a tight lid. The jar should hold about 2 gallons (7.6 L) of liquid so you'll have room to stir your mixture. Pour your brine over the top of the koji and stir it with a long-handled spoon. The thick koji paste will not dissolve into the brine, but the soy and Aspergillus will begin to seep into the water. [5]
  3. Keep the moromi in a place with a warm, stable temperature and stir it daily with your long-handled spoon.
    • As the koji ferments, it will probably produce a strong odor, so keep it covered tightly when you’re not stirring it.
  4. The fermenting process is what really allows the flavors to develop. You’ll need to give your soy sauce at least 6 months to ferment, although for a deeper flavor, you might want to wait up to a year. [6]
  5. Once you feel your flavors have developed enough, you should strain your moromi mixture. Place the solids in a press or a piece of cheesecloth to ensure you get all of the liquid out.
    • Discard the solids from this process.
    EXPERT TIP

    Vanna Tran

    Experienced Cook
    Vanna Tran is a home cook who started cooking with her mother at a very young age. She has catered events and hosted pop-up dinners in the San Francisco Bay Area for over 5 years.
    Vanna Tran
    Experienced Cook

    Did You Know? Fermentation results can vary based on the temperature outside of or inside your home. Natural fermentation happens best between 55 and 75 degrees Fahrenheit (13 to 24 degrees Celsius). If the weather is cold and your house is a little cooler than usual, fermentation might take a little longer; if it's hot outside, then your mixture might ferment faster.

  6. Heat your soy sauce over medium-high heat, then use a thermometer to ensure the mixture stays at this temperature for 20 minutes. Once you have finished pressing the mixture, transfer the liquid to a heat-safe pot and use a candy thermometer to monitor the temperature. Proper pasteurization will ensure there is no harmful bacteria in your soy sauce.
  7. Pour your pasteurized soy sauce into a container with a tightly-closed lid and refrigerate it. You may prefer to pour some of your soy sauce into a smaller container to make it easier to serve.
    • The finished soy sauce should last for up to 3 years if it's sealed and 1-2 years in an opened container. [7]
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Community Q&A

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  • Question
    Why do I have to use mold?
    Community Answer
    The molds make enzymes to help the fermentation process along, some turn starches into sugars usable by the lactobacillus and yeasts that do the fermentation process.
  • Question
    Where do I buy soy beans?
    Community Answer
    You can buy frozen edamame (not matured soya beans) in Asian supermarkets and also online.
  • Question
    Can I use soy bean powder instead of the bean pods?
    Community Answer
    No, boiling the beans is the best way. It just won't hold up if you don't use beans.
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      Tips

      • Soy sauce is an important ingredient in many dishes, such as hot and sour soup and various stir-fries. Be cautious about adding it in the right quantity, though, so the dish does not turn out to be too salty.
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      Video

      Things You’ll Need

      • Colander
      • Bowl for soaking soybeans
      • Long-handled spoon for stirring
      • Large pot
      • Press or cheesecloth
      • 3 in (7.6 cm) deep tray
      • 2 US gal (7.6 L) jar with tight-fitting lid
      • Candy thermometer
      • Bottle


      About This Article

      Article Summary X

      To make soy sauce, soak the soy beans in water overnight, then boil and mash them into a paste. Add wheat flour and koji starter to the paste and let the mixture rest for 2 days in a warm, humid place. Next, stir moromi into your base once a week for the next 6-12 months to ferment the mixture. Then, strain the mixture and heat the sauce to 175 °F to pasteurize it. Pour your sauce into an air-tight container and refrigerate it for up to 3 years! For more tips on fermenting and pasteurizing your sauce, read on!

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        Apr 14, 2017

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