Koji is steamed barley or polished rice inoculated with the Aspergillus oryzae culture. It is responsible for the fermentation process of not only amazake, but also miso and a number of other fermented foods. Our specific cultures can be used for amazake, rice milk, barley miso and rice miso, sake, shio koji, and pickles.
The basic difference between the types of koji is the ratios of the enzymes they contain: amylase (breaks down carbohydrates), protease (breaks down protein), lipase (breaks down fats) are the most common. For example, Amazake koji has a higher ratio of amylase (breaking down carbohydrates), Long Term koji has a higher ratio of protease (breaking down proteins), and Short Term koji has a more balanced ratio enzymes making it more of an “all purpose” koji.
The reason we use the terms “short term” and “long term” is because in recipes that call for short term koji the ratio of koji to soybeans is higher, making it ferment in a shorter amount of time and long term koji is called for when the ratio of beans is lower, making it ferment in a longer amount of time.