Soy fermentation

Besides tempeh, there are many soy products which are the result of fermentation, such as natto, miso, shoyu (soy sauce) and oncom.


Natto is a traditional Japanese food for more than thousand years. Natto are soybeans that are fermented by Bacillus subtilus natto bacteria. Natto possesses an odour of ammonia as a result of the break down of amino acids by Bacillus subtilis natto. During the natto fermentation viscous and sticky polymers (polyglutamic acid) are produces which makes the natto very slimy. Because of this odour and appearance, natto is not so popular anymore. During the natto fermentation Bacillus subtilus natto produces enzymes, vitamins, amino acids and other nutrients unique to natto. Some of the beneficial effects of natto include prevention of heart attacks, cancer, osteoporosis and intestinal infections. Natto bacteria have a strong enzyme, which can dissolve blood clots.


Miso is also a traditional Japanese fermented soy product. Miso is from koji mixed with rice, barley or soybeans. The miso is fermented and aged in wooden kegs. The lighter and sweeter types of miso are only fermented and aged during one to two months. The darker types of miso may be aged for up to 2 years and have a strong and salty taste. Japanese drink each morning a cup of miso soup, which is renowned to induce a health promoting effect for the consumer.

Shoyu (soy sauce)

Shoyu or soy sauce is a salty and brown liquid that is obtained by a lengthy fermentation of soybean and wheat mixture. First, the soybeans and wheat are blended with a starter culture (Aspergillus oryzae). The mixture is then allowed to ferment for a few days in large perforated vats. This culture, which is called Koji, is then tranfered to fermentation tanks, where salt and water is added. This mash, called moroni, undergoes a further fermentation of 6 months. After this period, the mash is pressed to extract the shoyu. During the soy sauce fermentation process, enzymes produced by the mold break down the soy proteins. As a result, most naturally fermented soy sauces contain no detectable levels of gluten (<5ppm) and can be considered as gluten-free. The taste and colour of shoyu depends on salt concentration, fermentation temperature and duration. Shoyu is very popular in Asian countries such as Japan and China. A major brand of naturally fermented shoyu is Kikkoman.


Besides tempeh, oncom is one of the traditional staple foods of West Javan cuisine. There are two kinds of oncom: black oncom and red oncom. Black oncom is actually tempeh but made from by-products, such as okara or peanut press cake, instead of whole soybeans. But red oncom is unique in that it is fermented with Neurospora. It is the only human food produced from Neurospora. In Europe the production and sale of red oncom is illegal because it is considered as a novel food. Novel food is defined as food that has not been consumed to a significant degree by humans in the EU prior to 1997, when the first Regulation on novel food came into force. So far no food product fermented with Neurospora has been approved.