According to A Primer on Brewing Makgeolli, a typical brew will finish fermenting in 7-10 days. Of course, there’s no exact science to predicting when a brew will be done, and it can be difficult—if not frustrating—trying to figure out if you should strain your brew. To that end, I wanted to write a post explaining the different tests you can make to decide if you’re ready to strain.
#1: LAYER TEST
While brewing in a transparent brewing vessel is not the most traditional of methods (I’ve been using a BPA-free bottle from Daiso), it does make it easy to see just how your brew is progressing. If you can see that your brew has separated into three distinct layers, it is probably ready to be strained. The bottom will be rice sediment, the middle will be an opaque, yellowish liquid layer, and the top will be a mushy rice cap.
The next three tests are if you are using a clay vessel like a hangari (or anything else where you can’t directly see what’s happening in the brew), you have to look for other signs. Here are the most common methods:
#2: MATCH TEST
Take off the lid of your brewing vessel and light a match. If the match goes out, it means fermentation is still active as it is producing C02. If the match stays lit, you are ready to strain.
#3: SURFACE TEST
When a brew is ready, there is often a clear layer of liquid floating on top of the rice cap. If you can take a spoon, push gently into the liquid or even the cap, and the spoon fills, your brew might be ready. Taste the brew and see what you think. This test is much less reliable than the Match Test but it’s worth keeping in mind.
#4: BUBBLE TEST
Look and listen to your brew. If the bubbling has stopped or is significantly reduced, there is a good chance your brew is done and it is time to strain. Without trying your hand at a number of brews, this one will be really difficult to use with any accuracy but at least it provides you with one more clue.
Note: Temperature will play a big factor in how fast your brew ferments. The brew will be done relatively quickly in hot temperatures and, conversely, it will take much longer in cold temperatures. The ideal ambient temperature should be between 18-26°C (64-79°F). Due to the warmth created by the fermentation itself, your brew will be about 5°C warmer inside the vessel.
*I’ll illustrate the Layer Test and Surface Test when I get some good pictures.