Conditioning Process of Nuruk
Just because you've made nuruk, it doesn't mean you can immediately start brewing alcohol with it. There's still work to be done. We call this process 'conditioning' or 'curing' the nuruk. This conditioning process refers to enhancing the medicinal and fermentative properties of the nuruk, and in traditional Korean practice, it often involves using water, fire, and sunlight. The effectiveness of the nuruk can vary significantly depending on how this conditioning process is performed. Since the process involves exposing the nuruk to outdoor air, it's important to ensure the surroundings are clean and dust-free to prevent contamination. In urban areas with high levels of fine dust, it might actually be better not to perform the process at all.
After fermentation, nuruk feels extremely hard to the touch and appears completely dry, but the inside often remains moist. To prevent spoilage, unpleasant odors, and improve shelf life, it's necessary to break the nuruk into coin-sized pieces and completely remove the moisture from inside.
During this conditioning process, the nuruk is dried in the sun during the day, which helps eliminate odors through exposure to wind. At night, it reabsorbs some moisture, which activates the microorganisms. By repeatedly going through this cycle of evaporation during the day and rehydration at night, the nuruk's saccharification and alcohol fermentation capabilities are enhanced, resulting in a more stable brewing process.
Order of Using Nuruk
To summarize the process of conditioning nuruk:
First, brush the surface of the nuruk using something like a brush. During fermentation, foreign substances and dust accumulate on the nuruk's surface, which can degrade the quality of your alcohol if not removed.
Second, break the nuruk into chestnut-sized pieces for conditioning. An important caution: don't grind it too finely. If the nuruk is too fine, it can easily be blown away by wind, and when making alcohol, fermentation may progress too quickly, potentially leading to spoilage.
Third, sun-drying is best for drying nuruk, and be careful not to let it get rained on.
Fourth, at night, the nuruk absorbs moisture and dew from the air, creating a favorable environment for the microorganisms inside. Since moisture can collect on the bottom surface, it's good to create an environment where air can circulate underneath as well.
Aging process
Ancient Korean texts record that "one-year-old nuruk is good, but two-year-old nuruk is not." Rather than using nuruk immediately after making it, it's better to let it age for at least three months. This aging process improves its fermentation power.
Once your nuruk is complete, you can place it in a breathable cloth (for those abroad, cheesecloth would work well) and hang it in a well-ventilated area to create nuruk with even better fermentation capabilities. However, there's one important caution: avoid this method if humidity is too high. The nuruk may reabsorb moisture and develop unpleasant odors. Therefore, it's best to avoid seasons or periods with high humidity.
The finished nuruk can be stored in a freezer. When you want to use it again, take it out and put it through the conditioning process for 1-2 days before use. This gives the microorganisms in the nuruk enough time to "wake up" again.
I've briefly summarized the use of nuruk. Nuruk is a fermentation agent created by wild yeasts. Unlike koji, its production process relies heavily on the natural environment. I don't believe that the fermentation agent alone determines all aspects of the alcohol. Good alcohol is born when the fermentation environment, the local water, and the fermentation agent all work in harmony.
However, it's a fact that the natural fermentation provided by nuruk produces results different from those of Japanese koji. I will continue to think about how to further commercialize and modernize nuruk for contemporary use.
