Nuruk (누룩) has been doing its work quietly for a very, very long time. It's Korea's ancient fermentation starter, and it's responsible for the character in Korean Sool that sets it apart from anything else in the world of fermented drinks. It also happens to be one of the most technically fascinating things we work with.
The simplest way to explain Nuruk is by contrasting it with Koji. Koji is a single, selected mould species - cultivated under controlled conditions, consistent from batch to batch, producing predictable (but delicious) clean fermentations. Nuruk is the wild child opposite of that. It's a compressed cake of grain flour (typically wheat, rice, or barley) that is exposed to the wild microorganisms present in the environment where it's made. Not inoculated with a selected culture. Not laboratory-controlled. Just grain flour, the right moisture level, and a little bit of starter mother, whatever is alive in the air, on the surfaces, even in the hands of the people making it. Over several weeks, a community of moulds, yeasts, and bacteria colonises the cake, and that complex ecosystem becomes your fermentation starter. It saccharifies and ferments simultaneously - doing in one step what requires two separate additions, and a whole complicated process of mashing in conventional brewing.
The difference Nuruk makes to the final drink is real and immediately perceptible. Koji fermentation tends to produce spirits that are clean and linear - the character of the base ingredient comes through clearly, the fermentation adds depth but not noise. Nuruk fermentation produces something wilder and way more layered. Earthier. Slightly sour. A complexity that's hard to pin down but completely distinct once you know what you're tasting. Traditional Korean distillers would tell you that Nuruk carries the "terroir" of the place where it was made and hat's literally true - the microbial community it contains is specific to the environment in which it developed.
Maybe this sounds a little "hmmmm" if you're hearing about it for the first time - letting all these things grow in what is essential damp wheat, but uruk has been made for over a thousand years and is scientifically proven to be perfectly safe. If you've eaten Korean food, you have already eaten nuruk, its in all the fermented pastes and many other dishes. The key here is correct temperature and humidity control, which our dedicated Nurukbang (or nuruk room) provides. Inside this room, in the same way as our Kojimuro, we have a precise control over every aspect of the climate, and are able to produce a delicious fermentation starter with our own natural biological agents.
Making Nuruk properly, and well, is slow and patient work. We grind our grain to a very course flour, and we then mix it with water to jussstt the right consistency. Its pressed into cakes, manually, and moved into the Nurukbang - our dedicated fermentation space where temperature and humidity are managed carefully through the growing period. The IoT monitoring we run across the distillery gives us all live data to work against, and data to improve future batches, but reading a Nuruk cake, understanding from smell and touch and appearance how it's developing, is something you just have to learn over time and batches and mistakes. Even then, as with the plethora of big and small brweries in korea that are using tradtional nuruk, its not guaranteed - it takes a month or more for a cake of nuruk to be ready, and until you break it apart you dont quite know how its gone, except for the trust in your senses. At this stage, we rigorously QA the cakes and triage out any that we don't think are up to a standard of quality for our brewing - its like opening a present, and hoping to get some cool ass Lego instead of a boring cardy.
All of our Nuruk is made right here in Melbourne. We have produced and tested over 50 different varieties, and have over the past year or two narrowed this down to four specific varieties that have different uses. We have a nuruk for soju, a nuruk for makgeolli, and nuruk for cheongju, an a general workhorse nuruk that covers all three .The wild yeasts and moulds that colonise our nuruk are from this city, from this particular little pocket of Northcote, right by the Merri Creek, and it is nuruk that cant be found anywhere else in the world.
And tbh, we think that is what really matters, not as some kind of hyped bs label claim, but as a genuine statement about what fermentation here at Tano actually is: a living process, inseparable from the place we call home.