Natto – Japanese Fermented Soy Beans
Last week it was nata, this week it’s natto. Though both are delicious (and maybe a little challenging by some standards) they are not otherwise easy to confuse. Nata is candy made from a kombucha, jun or vinegar SCOBY. Natto is an alkaline, Japanese, soy ferment that has had me smitten ever since I first read about its health benefits in (say it with me) The Art of Fermentation by Sandor Katz.
I had never tried natto before reading The Art of Fermentation, and after reading about it both there and elsewhere, I was intimidated. Descriptors given both in my reading and conversation with Japan-dwelling friends: slimy, mucilaginous, disgusting, okay when you eat it with a ton of mustard, not for non-Japanese, bizarre, gross, funky, stinky and unpleasant. That’s the short list. With those ringing recommendations, it somehow kept getting pushed down in the rankings on the to-do list of my experiments. When I finally tried some in a restaurant and, later, others from the freezer section of my local Japanese market, I felt something between disappointment and confusion. I was a little disappointed that natto wasn’t a bit more challenging and I was confused that everyone and their mother had described this food as slimy.
I hate slimy. A lifetime battle with mushroom hatred and an inability to swallow certain items from certain regional foods has taught me that sliminess is my food dislike. Natto is not slimy. If anything, it’s the opposite. Its changing web of strings and strands are on the sticky side. And I love them. My first through fifteenth bites of natto reminded me of a very toned down version of that time in the Peruvian rainforest when we snagged a few fruits from the latex tree. As you might imagine, fruit from the latex tree has some interesting qualities, the main one being that your lips stick together for hours after you eat it, with no relief available from soap or water scrubs (the ambrosial flavor makes it worth eating anyway). This is a way more exaggerated effect than the bit of cling you get from eating natto, but it was certainly a closer reference for me than anything mucilaginous that may have crossed my plate in the past.
The flavor is a little bit roasty, a little bit funky (think blue cheese) and a lot soy. For me, this is a wonderful thing. Like many others, I gave up unfermented soy under duress. I hit a pretty rough hormonal period (sorry, gents) and after an elimination diet, I learned that soy was the culprit for me. As a long-time tofu lover, I was pretty distressed. But a crying-for-no-reason-fit in the middle of the street, and a few horrible bouts of cramps convinced me that the sacrifice was worth it. Two years later, I’m my (arguably) sweet self all month long. But I do periodically get the strong desire to whip up a batch of super firm tofu and while natto doesn’t have a whole lot in common with tofu, the leguminous flavor does tame my soy-seeking beast.
Natto Health Benefits
Natto is special for another reason: those health benefits I mentioned above. While most fermented foods become alkaline during the fermentation process due to increased mineral bioavailability, natto is actually just an alkaline food due to its key fermenting bacteria Bacillus Subtilis Natto. (More information on that in The Art of Fermentation by Sandor Katz, pg. 329). Better yet, an enzyme is produced during fermentation that is both clinically proven to do amazing tricks and suspected of having a few others up its sleeve. Most importantly, this enzyme, nattokinase, has been shown to do in plaques in the arteries and is suspected of having a similar effect on plaques in the brain (aka those bastards who cause all kinds of neurological disorders like the plague of alzheimer’s). It is also used to tread tons of conditions, from heart disease and hemorrhoids to varicose veins and infertility. The many healthy properties are what had me sold, initially. With a strong desire to avoid all aforementioned plaques, this miracle food sounded pretty good to me. Now that I eat it regularly, I dig it for the flavor.
Why Make Natto?
I make natto for the same reasons I make most things: it can be hard to find organic natto and I’m not a fan of GMO soy. And, of course, homemade just tastes better. Homemade natto is simultaneously funkier than commercial and definitely more intensely umami (think red meat or blue cheese). We’ve been using it all kinds of places that break with tradition, including seasoning with barbecue sauce and making “natto pâté.” The soybeans I use tend to be larger than the soybeans I’ve had in commercial and restaurant nattos, so if you were/are a regular consumer of commercially produced natto, do be prepared for that difference.
Although there is some equipment needed for this process, if you can make yogurt, you can make natto. There are a couple things to consider, though: the amount of spore needed is TINY, so the quantity of beans you need to make is enormous (1 kilo of dried beans!). You need to be able to maintain a warmer temperature (~103F) for 24 hours. I do this with a heating pad with no off switch inside my oven. My experiments with culturing in jars did not go well, so I don’t think your typical yogurt maker is a good option here.
I bought my natto spores from Cultures for Health. The instructions included with the spores were good, but very focused on sterilizing everything in sight. I use my normal standards for fermenting when making natto, which for me means a very clean kitchen, clean implements, vessels and pots and no sterilizing.
- shallow dishes sufficient to hold 1 kg of soybeans after they’re hydrated and cooked (I used my pyrex 4.8 quart baking dish, my 8-inch square pyrex dish and my
- plastic wrap or aluminum foil (sadly, I’ve found that plastic wrap works best for natto in my home)
- a large pot
- a heating pad with no off switch or another device or process for maintaining a 104 degree temperature for 24 hours straight*
- kitchen thermometer
- a very large bowl, such as one you might use for sauerkraut production
- a kitchen scale (optional)
- 1 kilogram (2.2 lbs) dried, organic soy beans (seriously, buy organic, or you’re definitely getting GMO soy)
- 0.1 grams natto starting spore (bacillus subtilis natto)
- Rinse soy beans and remove stones and unwanted beans
- Place beans in a large container and add at least twice as much water as there are beans
- Soak for 12 hours. Once the soaking period is over, drain the beans and place them in a very large pot. Cover with water and bring to a low boil. Allow to boil for 5-6 hours or until beans break apart easily but are not yet mush.
- Strain the beans. Allow them to cool slightly, for about 30 minutes. While the beans are cooling, bring a 1/2 cup of water to a boil and allow it boil vigorously for 5 minutes. Remove from heat and let it sit to cool for 10 minutes.
- Add your tiny, tiny spoonful of natto-moto spores to the water and stir vigorously until the spore powder is dissolved.
- Pour spore liquid over your cooked beans and stir very thoroughly to distribute the spores as evenly as possible. I spend a good chunk of time stirring.
- Transfer inoculated beans to their culturing containers. I use my pyrex baking dishes (think lasagna, not loaf). You don’t want the sides very high and you don’t want the beans to be layered too deeply. 1-2 inches deep should do it. Cover containers with plastic wrap and place them on the heating pad in the oven, or use whatever contraption you use for incubation.*
- Wait 24 hours. Remove plastic wrap and stir beans. You should see the characteristic natto strings. The beans on the surface may look a tad cooked or wrinkled. It’s nothing to worry about. Stir the beans to integrate the guys who were on the top. You can eat your natto after a couple hours in the fridge or store them in the fridge for a week. I put half in the freezer as soon as it’s cooled. These quantities are not consumable by my family of two, and the freezer maintains their fun strands.
*There are many ways that one can do this. If you do it my way, use a kitchen thermometer to measure the temperature of the various heat settings on your heating pad before you start this process. Keeping it between 100F and 110F has worked best for me.