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Homemade natto - no stringiness :-(

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I've tried to make homemade natto several times now. The fermentation results in white frosted soybeans but there's no stringiness.

What should I do to make natto stringy?

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  1. My first guess is that it has not fermented long enough or at a warm enough temperature, but perhaps you could take us through your process and that might help us troubleshoot your issue a little better.

    5 Replies
    1. re: BigSal

      Here's my procedure:

      Soak beans 24 hours
      Steam beans 60 minutes in a pressure cooker

      Boil 1/2 cup of steam water with 2 tsp of sugar.
      When solution is cool add 0.1 g Nattomoto Powder

      Place the beans in two sterile oven trays
      Pour Natto Spore solution over beans, mix well and spread beans in a thin layer.
      Put an oven tray upside down on top and place in oven at 104F (40C)
      Ferment 24 hours.

      How soft should soybeans be in order to ferment well?
      How hot should liquid be in order to activate Bacillus Subtilis spores?
      Does an upside down tray on top make it too humid?
      Does salt play an important part of the fermentation process?

      1. re: zony

        I haven't used natto motto (I use natto as the starter), but I looked up how Natural Imports suggests using it and they do not heat the water that the powder is added to. http://www.naturalimport.com/natto_sp... Also, are you adding the spores to warm beans? Lastly, how are you covering the beans in the oven? It should not be airtight -tin foil with little holes to allow some air to get in. Also, does it smell like natto? Another thought- after fermenting, do you let it age for a day or so to further develop the stringiness?

        1. re: BigSal

          It's so convenient to use another oven tray as a lid but I suspect my set up is too air tight, making it too humid. Is frosted beans a sign of too high humidity?
          The beans are warm, not hot, and natto spore solution is 104F.
          It smells like natto and I let it age in the fridge but it does not improve stringiness.
          Perhaps the beans are not soft enough.

          1. re: zony

            Your beans should look a little frosted (grayish white film). It sounds like the oven tray may be preventing enough air to get into the natto to really ferment properly. Good luck. Gambatte kudasai! All this talk of natto is making me want some now. :)

            1. re: BigSal

              This instruction makes me puzzled:

              'Put sterilized cloth on the container and put on a lid .'

              Isn't the lid going to make it pretty airtight. When I use an upside down tray as a lid it's not airtight. I make sure air can pass through. At the end of fermentation the beans closest to lid openings are almost dry and have less frosting.

    2. Here is a great video that helped me make stringy natto: