Koji Starter Cultures for Soy Sauce

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Koji Cultures for Soy Sauce

Koji was first used in China (where it is known as qu) in 300 BC, and in Japan in 300 AD. As a fermenting agent, koji was a vital component in food preservation. Koji is a super star in fermentation and provides the main framework for major fermented soy foods:
  • Shio Koji - A condiment and marinade
  • Miso (fermented bean paste) and Tamari (wheat-free soy sauce substitute) 
  • Shoyu / Jiang You / soy sauce - The cornerstone of Asian Cooking
  • Rice vinegars
  • Sake (rice wine)
  • Amazake (sweet, non-alchoholic rice wine)

Why Ferment Your Own Soy Sauce?

Soy sauce is made either by fermentation which is slow or by acid hydrolysis which is a chemical process and rapid. 

Fermented Soy sauce: The taste is unbeatable. It is liquid gold. Each and every drop contains deep, complex and mellow umami flavours that elevate food to a higher level. Naturally brewed soy sauce has a reddish-brown color, and is well balanced in terms of flavor and aroma. This process takes 6 months to 2 years. Average cost in specialty stores: $36-60 for 1L.

Chemically produced soy sauce: The taste is brash and strong, and may have an astringent smell. Its dark color is created artificially using corn syrup, salt, caramel coloring and other additives. This process takes a few days to produce. Average cost in a regular grocery store: $4.5 for 1L

Can you see why we are fans of slow, fermented soy sauce? Due to the long time frame, it costs easily 10-15 times the price of cheap soy sauce, so we've started brewing our own... and now, so can you!

At Craft & Culture, get our soy sauce koji kin (麹) to start your soy sauce ferments! If you require more know-how, We also offer fermentation workshops as well! Please see here

Known scientifically as Aspergillus Sojae, this mould is first mixed with wheat flour and undergoes rapid mycelial growth on grains like soy, and secretes enzymes like amylases to digest carbohydrates into simple sugars when the koji is activated.

Upon addition to brine, a secondary fermentation process then happens, transforming in flavor and texture. It's how soybeans become miso, rice becomes sake, soybeans plus wheat become soy sauce. 

Famed chef David Chang of Momofuku describes it best: 
"Microbes produce enzymes, enzymes develop amino acids, glutamic acid + aspartic acid = umami, umami = delicious."

Here's a sample soy sauce recipe we use:

Soy Sauce Recipe: (makes 600-800 ml soy sauce)
  • 225g dry soy beans (~500g when cooked)
  • 2g soy sauce koji or half a teaspoon
  • 50g wheat flour (or rice flour)
  • 50-60g salt (10-12% by weight of cooked beans)
  • 500 ml water
  1. Soak the dried beans overnight and boil in water until they are soft and can be mashed with your fingers (usually 1-2 hours on high heat). Save some boiling liquid and set aside to cool.
  2. Roast the wheat flour over a low fire until the flour turns a pale brown colour. Set aside to cool completely.
  3. Mix the soy sauce koji and roasted wheat flour together. When the beans are at room temperature, toss them to coat with the koji-flour mixture
  4. But the beans into a pan, cover with plastic wrap and allow the mould to develop into a light green-yellow colour before transferring to your sanitized fermentation vessel. This process will take 2-3 days.
  5. Dissolve salt into hot water and allow to cool. When cooled, pour into vessel with beans and allow to develop and ferment, stirring weekly. Open the vessel to let in some air but take not to not leave the mixture exposed completely for extended periods of time.
    In one month, the sauce will be light, but the best flavours take up to 6 months and best if allowed to sit and darken for a year. 
  6. Filter out the beans and sediment through a cheesecloth and cover. Leave overnight. Heat the resultant liquid until simmering. Allow to cool and transfer into sauce bottles. That's it! The process is rather tedious but it's highly rewarding :)

Unit Weight: 20g (Makes 6 to 8 L of soy sauce) 

Each L of slow fermented soy sauce costs about $3-5 to make

Appearance: Olive green powder

Storage: Store in a cool and dry location, out of sunlight. 


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