Soybeans became widely popular in the last few decades. Low in fat, high in protein, a good substitute for meat, and sometimes fermented. This unassuming little bean has plenty of creative uses. Unfermented types of soy products include tofu, soymilk and in its purest, unprocessed form, edamame. Microbes transform soybeans into products as different as soy sauce, tempeh, natto, and miso.
When I first bought tempeh several years ago, I thought there was something wrong with it. A mysterious white substance glued soybeans together into a solid, congealed slab. It felt slimy and was full of grey spots. Little did I know at the time that microbes help make this tasty treat.
Tempeh, originating from Indonesia, is made from the fermentation of soybeans and grains. It has a firm, slightly chewy texture and a nutty flavor. To make tempeh, soybeans are soaked, hulled, and partly cooked. Then the fermentation starter and vinegar are mixed in. The starter contains a mixture of spores from the fungus Rhizopus oligosporus and Rhizopus oryzae. To create an environment that favors Rhizopus growth over other microorganisms, vinegar is added to lower the pH. The beans are spread out and fermentation continues for 24 to 36 hours around 30ºC. During this time, the fungal mycelium grows knitting the beans and grains together.
While the grey spots and congealed nature of tempeh don’t faze me anymore, natto is another beast. Natto is a traditional Japanese food and is said to be an acquired taste because of its slime, stink, and pungent flavor. Like tempeh, soybeans are soaked and cooked. Instead of mixing with fungus, the soybeans are mixed with a strain of the bacterium Bacillus subtilis (the strain was formerly called Bacillus natto). After 24 hours at 40ºC, the beans are refrigerated for one week for the Bacillus subtilis biofilm to develop creating even more stringiness.
Fermented soy products are said to be more beneficial than their unfermented counterparts. Soy naturally contains high amounts of the antinutrient phytic acid. Phytic acid binds minerals such as zinc, calcium and iron preventing your body from absorbing these nutrients. Due to B. subtilis fermentation, natto contained less phytic acid than unfermented soybeans. But will I be brave enough to try natto? Perhaps one day.
