What is Koji?

The ingredients for our award-winning miso are simple –organic rice, organic soybean/chickpea, and sea salt. But where do the rich umami, sweetness, and aroma of miso come from? The secret is Koji – rice fermented with our microscopic friends – Koji culture (Aspergillus Oryzae)!

Koji is made by inoculating steamed rice grains (or other grains and legumes for that matter) with Koji culture and fermenting for 40-48 hours in a warm environment. Koji is used to ferment not only miso but also soy sauce, sake, rice vinegar, mirin, and shochu (distilled liquor) which are all absolutely essential in Japanese cuisine.

Koji culture was discovered and isolated from nature more than 1,000 years ago, long before microscopes were invented, and has been passed down over generations of koji manufacturers in Japan. Given its significance, it was declared Japan’s “National Fungus” in 2006!


What does Koji do?

Koji is an enzyme powerhouse, producing more than 100 enzymes, including those that break down starches (e.g. rice) and proteins (e.g. soybean) in the culture medium turning them into digestible glucose and amino acids which can then be used by yeast and lactobacillus for secondary fermentation. Furthermore, Koji produces vitamins (including B1, B2, B6, B12, K, and folic acid) and minerals adding nutritional value to your food.

Koji is great in fermentation but can also be used in everyday cooking to bring out the flavour of the ingredients, especially “umami”* and sweetness. Another benefit, especially when working with proteins such as meat, is that it can predigest, tenderize and speed up the aging process in just a few hours.

* Umami is the savoury flavour discovered by Japanese scientist Kikunae Ikeda in 1908 as the fifth taste sensation following sweetness, sourness, saltiness and bitterness. For more information please click here.


How can I use Koji?

Koji can be used as a fermenting agent in traditional Japanese fermentation such as Miso, Soy Sauce, Tamari, Sake (rice wine), and Mirin as well as in all sorts of other fermentation projects such as pickling, and breadmaking. The possibility is endless!

However, the most popular and easiest way of using Koji at home is to make Shio Koji (Salt Koji) and Amazake Jam (Sweet Koji) or use it in powder form – simply by sprinkling over your food to add umami and enzymes!


What is Shio Koji?

"Shio" means “salt” so Shio Koji means Salt Koji and is a liquid seasoning and can be used as a healthy alternative to salt. It is a traditional seasoning from the Tohoku region of Japan and can easily be made at home by mixing Koji, salt and water and fermenting on bench top for 7-10 days (depending on season).

It is full of amino acids and peptides which add “umami” to your ingredients. In addition, the enzymes in Shio Koji break down the proteins into amino acids, and starches into sugar, “predigesting” and bringing out the flavours of the ingredients. Koji contains more than 100 varieties of enzymes that can breakdown different proteins and can work as a meat tenderizer and tenderize various meat, fish, or even cheese and tofu.

Click here for how to make Shio Koji and recipe ideas


What is Amazake?

Amazake means sweet sake but does not contain alcohol (though it starts turning into alcohol when fermenting process continues). It can be made by adding Koji into rice porridge and maintaining the mixture at 60 degrees C for 8-12 hours. The enzymes in the Koji breaks down the starch in the porridge turning it into glucose and oligosaccharide, and the end result is a super sweet drink made 100% from rice!

Amazake contains Vitamin B1, B2, B6, folic acids, fibres, oligosaccharide, amino acids such as cysteine, arginine, glutamine and lots of glucose, which is similar to what is in intravenous drip, so it is also known as “the drinkable drip” in Japan. In the Edo era (1600-1800s), it was enjoyed as a summer energy drink. The oligosaccharide in Amazake is a great prebiotic that acts as food for "good" bacteria in the intestine.

You can dilute amazake with water to taste, or mix with milk, or soy milk and enjoy as latte, or use it as a natural sweetener in your sweets, smoothies or yogurt.

Click here for how to make Amazake