I want to thank Stephan at Biohacks.net for sending me an email about natto. I was well aware of how healthy the Japanese ferment was, especially its very high vitamin K2 levels. What I didn’t know until I researched it further was the fermentation time was just 24 hours. For some reason, I had always assumed it was much longer.
Fellow Weston A. Price fans that read his book Nutrition and Physical Degeneration will recall the author theorized there existed a vitamin like activator. That “Activator X” turned out to be Vitamin K2. Chris Masterjohn wrote On the Trail of the Elusive X-Factor: A Sixty-Two-Year-Old Mystery Finally Solved for the WAPF site.
You May Not Like the Taste
Natto is fermented soybeans. They are slimy and have a weird texture. Most people I talk to have either never heard of the food or dislike it. Natto was one of the few non-animal parts foods to make it into the book Yuck! The Things People Eat. Here is how that book describes natto:
Sticky, smelly, slimy and with an unpleasant aftertaste.
Although I agree the texture is odd, it has always tasted fine to me, especially over rice with some mustard or soy sauce.
Why Make Your Own?
Before we proceed, I though I’d mention my two motivations for making my own natto. The primary reason is the pre-packaged nattos sold at the Asian grocery store are loaded with crap we don’t want to eat. Seattle’s Uwajimaya is a nice grocery store and they sell probably 20 different brands of natto. However, they all have some nutritional defect. Soybean oil, MSG, wheat, or things listed I can’t even spell. For my natto, I picked the cleanest one. I wanted it for culture. Once I was up and running, I wouldn’t need to return to Uwajimaya for more natto.
The second reason I decided to make my own is because I love to ferment. It is a cool hobby. Check out my Fermentation page for other ideas.
Enough with the background, let us make some natto.
- organic soybeans – I got mine in the bulk section of a local grocery store
- a single packet of natto for the culture
- an incubator that you can use to hold a temperature of ~104 F for 24 hours
- stock pot and steamer
- container to hold ferment – I used a small glass Pyrex pan
I live in a city with a Japanese grocery store, so acquiring some pre-made natto was not a problem. Look for it in the refrigerated section. If you can’t acquire natto where you live, there are places online that sell cultures, including eBay.
I used a little over 6 ounces of soybeans. This is a small amount, but I wanted to error on the low side for my first ferment, in case I messed something up. Spoiler alert: I didn’t mess anything up. 🙂
Build the Incubator
According to Natto King, the fermentation needs a stable temperature between 100-113 F. My oven is too warm as is my slow cooker. Although some slow cookers with a Warm setting might work with a water bath. See Making Natto in North America on Umami Mart for info on that method.
I decided to use a directed light inside a styrofoam cooler. I got the idea from chicken farmers that build their own egg incubators. Mine would be a simple version of theirs.
About 15 minutes after I turned on my lightbox lamp light, the inside of cooler jumped to 107 F. Perfect
Soak the Soybeans
After rinsing the soybeans, I covered them in filtered water and let them soak overnight. They will triple in size.
Steam or Boil the Soybeans
I steamed the soybeans in my stock pot for 1 hour. You could also boil them or use a pressure cooker.
Mix Natto Culture into Cooked Soybeans
Before I forget, while the soybeans were steaming, I put my Pyrex pan in the oven at 250 degrees to sterilize it. Got that idea from Umami Mart. Mix the cooked soybeans with the package of natto. I added a little bit of hot water to the packaged natto to loosen it up for stirring.
Cover and Ferment
I covered the Pyrex with foil, poked a few hole so it could breath and set it into my incubator. I monitored the temperature and let it ferment for 24 hours.
Here is the natto after 12 hours.
Natto at 24 hours
Refrigerate and Wait
I had a small sample at the end of the ferment that I was pleased with. However, most of the online resources say that the flavor of natto continues to develop for a few days to two weeks. That it did. More gooey fun!
During the fermentation, I didn’t smell anything. That could be because I used a small amount covered or maybe its odorous reputation is unwarranted. I’ve never considered it a stinky food. Slimy yes, stinky no.
Next week I will make my second batch of natto using a culture from the natto I made. I will also attempt the WARM setting on my backup slow cooker, although I am concerned it will get too warm. I’ll be certain to update this post with that information.