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Black oncom starter culture


In stock

(3 customer reviews)

Oncom is a traditional fermented product from Java. It is made from soy grains that are left over after preparing soy milk and/or tofu. No waste tempeh!

In stock

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What is Oncom?

Oncom is a traditional fermented product from Java. It is made from soy grains that are left over after preparing soy milk and/or tofu. There are two varieties: black and red oncom. The first one looks like tempeh and is fermented with Rhizopus oligosporus. Red oncom is made with Neurospora intermedia var. oncomensis. The starter for sale is meant for Black oncom.

Other sources for oncom are the leftover bits of grinding tapioca meal or peanuts Here you can read more about oncom (English, Google books).


  • 20 grams, which is enough for about 4 to 5 kg black oncom
  • Ingredients: Black Oncom starter (Rhizopus oligosporus) and rice flour
  • Storage instructions: keep in the fridge for at least 6 months, more than a year in the freezer
  • Country of origin: Indonesia
  • Allergens: none

How to make Black Oncom


  • sieve
  • clean handkerchief
  • hand blender / blender
  • A ziplock bag, plastic disposable cup or plastic sausage casing 
  • A warm place where it is 25-35 ° C (e.g. oven,  multifunctional fermentation cabinet or the box that you also use for koji)
  • thermometer
  • fork or pin


  • 200 grams of dry soy beans
  • 1 gram of Black oncom starter
  • 15 ml of vinegar


  1. Allow the soy beans to soak overnight in water.
  2. Drain and add about one tot 1.4 liter of fresh water. Puree the soy beans with the water with a hand blender.
  3. Squeeze .
  4. Use the soy milk to drink, or to make tofu.
  5. Cook the soy meal (okara) gently with some added water for about 5-10 minutes.
  6. Squeeze and let it cool down.
  7. Sour cooked okara by mixing it with vinegar.
  8. Start the beans with about 1 gram of starter culture. Mix the mold with the beans.
  9. Pack the beans tightly in a plastic bag or container and puncture with a fork or needle every few centimeters. The fungus needs oxygen, but not too much.
  10. Leave it to ferment at any temperature between about 25 and 35 ° C . Expect it to take around 3-4 days at 25 ° C and 18-24 hours at the other end of the spectrum. The growth of the mycelium of the fungus creates a compact cake.
  11. The black oncom keeps well in the fridge for a few days.
  12. Fry with lots of oil until the outside is crunchy.

Online English spoken workshop ‘how to make your own miso’Fermentation workshops

During this online master class, Dutch foodwriter and fermentation expert ‘Meneer Wateetons’ will teach you how to make your own miso. Thanks to a special form of fermentation, two very modest and rather boring ingredients come together to form one of the most beautiful, complex substances on earth. Mister Wateetons tells you exactly how that fermentation works and what you need for it, how you can make miso at home from now on, how you can speed up the process of making miso, how you can vary endlessly on these two basic ingredients and what kind of cool things you can do with miso. Click here for more info.

3 reviews for Black oncom starter culture

  1. Roland N. (verified owner)