In Northern Thailand, fermented soybeans, the
so-called “thua nao”, have been produced and
consumed locally for several decades. Conventional
production of thua nao is as follows: soybeans are
washed, soaked overnight, cooked by boiling for
about 3 – 4 h, gently smashed and wrapped inside
banana leaves. The fermentation generally proceeds
for 2 – 3 days at ambient temperature.1,2 Alternatively,
the soybean products are allowed to ferment
outdoors exposed to sunlight, resulting in a dried
form of thua nao that can be kept for several months.
Its use is versatile, and fresh thua nao, for example
can be consumed by steaming or roasting while the
dried products are important ingredients in a variety
of local dishes.
Similar fermented soybean products have been
described in several countries, ie kinema in India,3-5
schuidouchi in China,6
and natto in Japan.7
Other
related products (ie ugba and iru) made with legume
seeds instead of soybeans have also been reported
in Western Africa.8,9 Among these, only a few
fermented soybean products have been studied
systematically and manufactured industrially. The
best-characterized fermented soybean product is
probably natto—the Japanese styled fermente