Kuchikamizake, which gained worldwide fame due to its presence in Makoto Shinkai’s Your Name movie, could originally have been a deadly poison according to twitter user Takeshi Ishitake (@_596_).

Kuchikamizake, also known as mouth chewed sake, is made by putting rice or other food in the mouth, chewing it, and then spitting it out to let the sake settle and ferment. In Japan, however, the sake making process involves one more ingredient, the rice koji mold.

The koji mold (scientific name Aspergillus oryzae) is a fungus which is used in sake making. The rice starch in the mix is converted into sugar, which is then converted into alcohol by the fungus.

However, Takeshi pointed out that the koji mold, which is unique to Japan, is a derivative of the Aspergillus Flavus strain of fungus. And this is where the problem starts.

Aspergillus flavus too does the same job as the koji mold, converting the starch to alcohol, however in doing so, it also produces a deadly side product called the aflatoxin.

The user then went on to list some incidents aiming to prove how deadly of a poison aflatoxin was.

• In 1960, over 100,000 turkeys died in the UK. The cause was discerned to be aflatoxin, which was produced by Aspergillus flavus.
• India and Kenya too have reported over 100 deaths because of this toxin
• Aflatoxin B1 is also said to be the most potent natural carcinogen.

Despite all of this surrounding Aspergillus flavus, Takeshi claims that the scientists never explained how the koji mold, which belongs to Aspergillus family, turned out to be non-toxic.

The National Library of Medicines says the following about how the fungus may have originated.

There are two scenarios to be considered for the origination of koji fermentation. In the first scenario, A. oryzae may have been isolated from nature independently in Japan. A literature describing naturally fermented alcoholic beverage was found in a historical document, Harima no Kuni Fudoki, edited in AD 715. Another historical document described that koji must be isolated from the mold growing on an ear of rice. This means that A. oryzae may have existed in nature before domestication and might be isolated from other dangerous species such as A. flavus through the method indicated in the historical literatures above. In the second scenario, A. oryzae may have been imported from China during the Yayoi period. 

In fact, the koji mold was even certified as Japan’s national fungus.

“As far as I know aspergillus flavus, if you continue to grow in a non-toxic environment it doesn’t produce poison. Did they take advantage of that?” Takeshi wrote in their tweet.

Initially kept secret, the rice koji mold genome was released by a consortium of Japanese biotechnology companies in late 2005. However, its uses can be traced back to late 1800s in Japan.

Koji mold has been used in the production of kuchikamizake, even in the late 1900s, as seen in a news clipping from Awamori news.

Source: Twitter