History of Natto and Its Relatives (1405-2012 - SoyInfo Center

eturning to the Hamamatsu area in central Japan, he donated
land to makers of hamanatto to encourage their craft.
Later, when Tokugawa Ieyasu took over Hamamatsu
castle, he used hamanatto as soldiers’ provisions. Each year
the local monks gave hamanatto as a gift to the shogun, who
in turn used it as a New Year’s offering. Still later, produced
by temple cooks and craftsmen, it was given as a New Year’s
gift to parishioners; it also had a symbolic meaning since the
word for soybeans (mamé) has also come to mean healthy
and robust. In 1968 Yamaya, a producer of tamari shoyu
(soy sauce) under the direction of Suzuki Yasuke, attempted
to make an improved version of the product previously
prepared at Daifukuji temple and fi rst affi xed the name
‘hamanatto.’ Thus the name of the product developed in the
following order: shiokara-natto (‘salty natto). kara-natto
(T’ang dynasty natto), hamana-natto, and hama-natto. To
this day, Daifukuji has maintained its own special method of
production, but this too has been commercialized.
Methods of production: Today hamanatto is prepared
by two methods: the traditional method handed down from
generation to generation since ancient times, and the modern
industrialized method which made improvements on the
traditional method without harming the special fl avor and
aroma. Yamaya company and Horinji temple use closely
related methods; the former is industrialized while the latter
is a handmade process using koji starter. Daifukuji uses a
different traditional process without koji starter since the
ancient incubation room, wooden trays, and rice-straw
covering mats are each permeated with starter mold spores.
The soybean koji (molded soybeans) is combined with brine
and put into vats for the second fermentation in September.
Since the room temperature during the koji making (fi rst
fermentation) is 20º to 25ºC (68-77ºF) no special incubation
heat source is needed. Yet since the molds propagate
naturally, without special inoculation, the koji making takes a
long time, up to ten days.
There are numerous points of difference from regular
miso production; when making salty natto [fermented black
soybeans] the soybeans are not crushed; the koji is incubated
with brine in a keg or vat with a heavy pressing lid; and
the fi nal product is sun-dried. At the factory, the soybeans
are only partially reconstituted [by soaking in water] until
they reach 1.5 to 1.6 times their dry weight; this takes 2
hours in winter and 1½ hours in summer. They are then
drained and allowed to stand for 4-5 hours so the absorbed
water penetrates deeper. If they are drained for too long, the
beans become hard. They are then steamed for 4-5 hours
[at atmospheric pressure] and allowed to stand overnight in
the steamer. At Daifukuji, the unsoaked beans are dropped
into boiling water, parboiled for 7-8 minutes, steamed for
7-8 hours in a 2 meter deep steamer, then allowed to stand
in the steamer until the next morning. Care is taken that
the beans are not crushed or dehulled. Nowadays, since it
is known that the process of leaving the beans overnight in
© Copyright Soyinfo Center 2012
HISTORY OF NATTO AND ITS RELATIVES 229
the steamer lowers their net protein utilization and makes
them more diffi cult for the enzymes to digest, this step is
generally omitted. Traditionally it was always used to darken
the beans; there were apparently no problems with bacterial
contamination, perhaps because the reaction of sugars and
amino acids under heat produces substances which reduce
the proliferation of bacteria and yeasts. In fact, the overnight
period in the steamer may have been done expressly to
encourage this effect. Continued.
671. Ito, Hiroshi. 1976. Hamanattô [Hamanatto (Continued–
Document Part II)]. Nippon Jozo Kyokai Zasshi (J. of the
Society of Brewing, Japan) 71(3):173-76. March. [Jap; eng+]
• Summary: Continued. The steamed beans are then spread
on a thick rice straw mat (mushiro), drained well, sun dried,
sprinkled with roasted barley fl our, and mixed until each
bean is well coated. The straw mat helps to absorb excess
water. In factories, the roasted fl our is premixed with koji
starter (Aspergillus oryzae mold spores), they dried the straw
mat and used it year after year. Molds such as A. oryzae, A.
soyae, and Rhizopus species inoculated the beans during
mixing with the fl our. The mixture is covered for one night
with rice straw mats, then the next day transferred to wooden
koji trays, which are arranged in the koji incubation room
to make koji. Care must be taken that excess heat does not
develop during fermentation, lest alien bacteria proliferate
and the product’s fl avor and aroma decline. To prevent this,
the koji mycelium is broken up three times by hand in the
trays during the incubation.
At factories, the fi nished koji is sun-dried for 4 to
5 hours in winter (Hamamatsu is famous for its dry fall
winds) or for 2 hours in summer so that the moisture content
is reduced to below 30 to 35 percent. IF this drying is
insuffi cient, after the beans have been put into the vats they
easily get crushed. The vat used is a 19-gallon wooden vat or
a small wooden tub. The koji is divided among several vats,
brine made by combining salt with boiled water is added, a
pressing lid equal to twice the weight of the vat contents is
set in place, and the mixture is allowed to ferment for 80 to
90 days in summer or 150 days in winter. (In some places
(Daifukuji), unpasteurized shoyu is used in place of brine).
The use of a heavy pressing lid is preferable since it
causes the fermentation to proceed slowly; a light one helps
it to go faster, but the soybeans more easily lose their form.
At temples they sliver the middle skin of sansho seeds and
place these at the bottom of the vat, then add the fi nished
koji and fi nally the brine. In factories they add a more
concentrated brine and ferment the mixture for at least 2
months. The fermentation room (kura) should have good
air circulation and ventilation, otherwise the product may
develop and unpleasant moldy or musty odor.
After draining off the brine scooping the beans out of
the vats, they are spread on rice straw mats (traditionally
mushiro from the Ryukyu islands; today tatami matting),