What is koji
Koji, Aspergillus oryzae, in Japanese 麹, is a filamentous fungus, or a mould, which is used in several Asian cuisines, to allow saccharification of several cereals, tubers and soybean.
It is used in the production of soya sauce, miso, mirin and of course in the that of several alcoholic beverages, including, Sake, Honkaku Shochu and Awamori.
Koji was mentioned for the first time in the book of rituals of the Zhou dynasty of China, in the fourth century before Christ.
Koji is largely used for four main reasons: it grows rapidly in cereals such as rice and barley, it produces a strong amylase secretion which facilitate saccharification of starches that are abundant in cereals and tubers, has a pleasant perfume and does not change food colour.
There are three main varieties: white, yellow and black koji, which are used in different regions of Japan, depending on the local climate and the product one wants to obtain. Shochu is mainly produced with white koji, while black, or kuro-koji, is the only one allowed to make Awamori in Okinawa. However, black koji is also used in the southernmost regions of Kyushu.
Yellow koji is used indirectly when sake-kasu, which is the residual of rice fermented must after pressing, during sake production process, is distilled into Shochu.