Koji, is the heart and soul of the distillery. You can learn a lot about a culture through what it chooses to ferment, and what it uses to do the fermenting. In Japan, the answer to that second question is Koji, and it explains a remarkable amount about why the food and drink of those places tastes the way it does.
Koji is scientifically known as Aspergillus oryzae, a mould that has been cultivated in East Asia for at least a thousand years, probably longer. It grows on steamed grain (rice or barley, usually) in warm, humid conditions - our koji room usually runs between 30-32c and 70-80% humidity, depending on the phase of the koji growth.. As it grows it produces enzymes: amylases that convert starch into fermentable sugars, proteases that break proteins into amino acids. It's doing the same fundamental job as malted barley in whisky or beer — creating the fermentable sugars that yeast needs — but the flavours it generates are completely different. Richer, more complex, with that quality people call umami that's difficult to describe but immediately recognisable when you taste it.
Koji is the reason miso is miso. It's why soy sauce is soy sauce. It's the foundation of saké, shochu, doenjang, rice vinegar and hundreds and thousands of different fermented foods across the region. Right now it's also one of the more exciting things happening in food culture globally - chefs have been working with it for years in places you might not expect, because the enzymatic activity it produces turns out to be genuinely useful for all kinds of things beyond traditional fermentation. Its use is growing in popularity immensely, and we'd be surprised if you haven't seen some kind of menu item incorporating it during your dining experiences.
At Tano we work with three different strains, each producing a distinct character. Black Koji (Aspergillus awamori) is our primary go-to for Shochu and its what makes Awamori what it is - its bold, robust, with high citric acid production that acts as a natural protection against contamination, which is part of why it developed in Okinawa's warmer climate. White Koji (Aspergillus kawachii) - clean, slightly citric, producing bright and lifted fermentations. Yellow Koji (Aspergillus oryzae) is the most delicate of the three, producing the highest enzyme activity and the most floral, layered character - we don't use this much, but you'll see it making an appearance in our green tea shochu and some other places.
Growing Koji isn't something you can set up and walk away from. The grain is inoculated at a specific temperature and moisture level, then checked and hand-turned at regular intervals through the growth period. The mould generates its own heat as it develops left alone it will overheat and stress or die, left unchecked and it can get over 45c and destroy the batch.
Our Koji room also runs a full suite of IoT sensors for temperature and humidity control that feed live data through the distillery systems (and we can check everything right from our phones or our dashboards throughout the distillery), which in turn also managed automated vents in the room. The vents to help the room stay stable and allow for some air exchange (growing koji produces a lot of CO2) but the actual decisions, is this ready, does it need turning, oh god, the turning and mixing and cooling it down at 2am), what does it smell like and how that scent changes and what it means - those stay human, and they always will.