How to know when your 1st ferment is done + ready to bottle
What is 2nd fermentation (a.k.a. F2)?
2nd fermentation is the process through which you flavor your brew and put it into a sealed container, which will trap the carbonation into the liquid as it continues to ferment.
It’s essentially bottle conditioning (similar to how in beer and champagne-making, you add a little bit of priming sugar, then seal it up to let yeasts eat up the sugar and convert it into carbon dioxide). That’s what makes it fizzy. In the case of kombucha, that added sugar typically comes from fruit.
So how do you know when your kombucha is “done” or ready to bottle for F2?
The basic answer is that it’s ready when it tastes done to you.
But what does that mean?
It should have an acidic/vinegar-like but not overpowering smell.
When you taste it, it should still have a bit of sweetness to it and a pleasant amount of acidity. If you want it to be more acidic, then keep fermenting it longer. If it tastes sour enough, then you’re ready to bottle.
I tend to like bottling when it's just a little too sweet for my liking (knowing that sugar will continue to get eaten away during F2 in the bottle).
Just remember that you’ll also be adding some sugar from the fruit or other flavorings during F2 in the bottle. Again, some of that sugar will get eaten up and converted into carbon dioxide, but it’s just a matter of finding a happy timing and flavoring balance that works for your taste preference.
Another quick note on “doneness” — after around 5 days in the vessel, the brew is ready to drink as-is. It’ll already be inoculated with that great, live bacteria. Some people like to drink kombucha right after F1, and that’s totally fine. You do not need to flavor and bottle your kombucha before you drink it.
However, if you want to flavor your kombucha and create more carbonation to make it flavored, fizzy beverage, you have to go through a second fermentation process in an airtight bottle.
How and when should I taste it?
Some say you can taste it throughout the F1 process to check for sweet and sour levels. You certainly can, but I don’t recommend messing with the vessel for the first few days. That way, the SCOBY can form uninterrupted. During the first 4-5 days, it’ll likely be too sweet anyway, so it’s not worth bothering your vessel just to sneak a taste.
For first time brewers, I recommend that you start tasting around day 5 or so. But you may not need to taste as often (or at all) once you get more familiar with your average brew cycle. I usually don’t taste until day 7 or 8.
I use a wine thief, but you can use a clean straw or a ladle to pull out some liquid to taste. Don’t worry about agitating the SCOBY once it’s mostly formed or once the 5-day mark has passed.
Can pH tell me when my kombucha is done?
A common misconception is that you can measure the pH to see when it’s done. pH is not an indicator of doneness, and it’s not an indicator of sweetness. The best way to tell if it’s done is to taste it. But if you’re curious about kombucha and pH, you can read my post about it here.
So whenever your brew tastes right to you, you’re ready to move on to the next step: bottling a.k.a. 2nd fermentation.