Originally found in Southeast and East Asian regions, Tane koji is described as spores of Aspergillus oryzae. Traditional Japanese fermentation industries use Aspergillus oryzae to produce soy sauce, sake, bean curd seasoning, and vinegar (among the many). A variety of enzymes are secreted by filamentous fungi. Since the 13-15th century (Heian and Muromachi period), filamentous fungi inoculations have been commercially available as ‘koji’. This suggests that it was cultivated without knowledge that it is a microorganism. Therefore, the word ‘koji’ refers to both the material fermented by Aspergillus oryzae in the form of Solid State Cultivation (SSC) and the Aspergillus oryzae microorganism itself.
Aspergillus oryzae, the koji mould
Traditional Japanese fermentation uses Aspergillus oryzae (rice grain, soybeans, and wheat bran). A similar style of fermentation may have originated in China 3000–2000 years ago. In Japan, they started to use this technology during the Yayoi period (B.C. 10th–A.D. 3rd).
Nowadays, If you want to produce koji, you will need to sprinkle Aspergillus oryzae over a base of rice, barley or soybeans base. Using rice, barley, and soybean as energy sources, the microorganism will obtain sugars and proteins from carbohydrates (starch) and proteins. Therefore, whether you use rice or barley or soybean as a base, each final product will have different characteristics.
In Japan, people still use koji to prepare traditional fermented foods, including soy sauce, miso, sweet rice wine, vinegar etc. Recently, koji has attracted quite a lot of food industry interest thanks to its functional properties related to flavour formation. Consequently, this could be a strategy to reduce sodium in the formulation of products like plant-based meat.
In a situation where consumers are more and more demanding plant-based products that mimick conventional meat and seafood, koji can help from the point of view of flavour. Some companies are already starting to use it in their food formulations and an example is US company Prime Roots which is selling koji-based bacon. The product has gained much popularity right from the very first launch day thus highlighting greater consumer acceptance of the product.
Some brands, like Japanese company SOI, are also using asp or as a tool for upcycling food industry by-products. SOI uses koji to ferment coffee grounds, turning them into functional coffee bars formulated with 0, 10 and 40% sugar. Another US startup, Shared Cultures, ferments local produce such as mushrooms with koji, which it says reduces food waste thanks to the natural preservation properties of fermentation.
Masayuki Machida, Osamu Yamada, Katsuya Gomi, Genomics of Aspergillus oryzae: Learning from the History of Koji Mold and Exploration of Its Future, DNA Research, Volume 15, Issue 4, August 2008, Pages 173–183, https://doi.org/10.1093/dnares/dsn020
How do you create meaty flavors in plant-based meat: https://www.foodnavigator-usa.com/Article/2019/08/22/In-conversation-with-Givaudan-How-do-you-create-meaty-flavors-in-plant-based-meat