Health benefits of Japanese Koji

Saga University Kitagaki Laboratory

Koji is the Japanese traditional fermented food which has a history of more than 760 years.
This site introduces academic health information about Japanese koji.

What is koji?
Koji is steamed rice fermented with nonpathogenic fungus, Aspergillus oryzae or A. luchuensis.
By utilizing the property that these fungi secretes abundant starch-degrading enzymes, it has been used as the starch-degrading (saccharifying) reagent in the production process of fermented foods in Japan. Koji is contained in most of Japanese fermented foods as the saccharifier of starch contained in crop cereals.

Are koji and Aspergillus safe?
Since koji has been ingested by Japanese people for a long time, USA FDA admits koji as GRAS (Generally Regarded as Safe).
Recent genomic analysis shows that A. oryzae and A. luchuensis does not have functional genes to produce mycotoxins such as aflatoxin (Nature. 2005; 438(7071):1157-61.).

History of Koji
Food fermentation using fungus is described in Japan in 713 AD, and food fermentation technologies using koji are described in detail in 970 AD. Since a battle of the koji industry sponsored by the Kyoto Kitano Academic Shrine, one of the most influential shrines in Japan, and the fermentation industry occurred in 1246 AD, microbiological methodology has been established. Therefore, it is considered that before 1246 AD, A. oryzae had been isolated and utilized in the industry in Japan.

Japanese traditional foods which use koji
Koji drink Amazake (Rice drink saccharified with koji)
Sake (alcoholic drink) koji is used as the saccharifier of starch in rice
Osu (Rice vinegar) koji is used as the saccharifier of starch in rice
Kurosu (Black rice vinegar) koji is used as the saccharifier of starch in crops
Shochu (distilled alcoholic drink) koji is used as the saccharifier of starch in crops
Health benefits of koji
Koji contains abundant beta-glucan, which stimulates immunity through macrophages (The function of beta-glucan is described in Blood, 108:3168-3175, 2006).
Koji contains glycosylceramide, which has improving effects of skin and intestinal microbial flora (Published in SpringerPlus, 5, 1321, 2016).

Koji-containing fermented foods such as Amazake (koji drink) contain less milk-derived lipids, thus decreasing cardiovascular diseases.

Professor, National Saga University, Hiroshi Kitagaki, Ph. D.

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