Guide to Homemade Kombucha -
Step 2: Second Fermentation
So you’ve already gone through your 1st fermentation cycle and are familiar with what to expect there. If you’ve already read my post on how to know when your 1st ferment is done, then you’re ready to bottle!
What is 2nd fermentation (a.k.a. F2)?
Second fermentation is the process through which you flavor your brew and put it into a sealed container, which traps carbonation into the liquid. It typically takes 2-4 days, but can take longer.
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.
1. Add 1/4 - 1/3 cup of pureed/juiced fruit into each 16 oz. bottle*. Most of my gallon batches yield approx. 7 bottles.
Read what types of bottles work best for F2
2. Remove your SCOBY and 2 cups of kombucha from your brewing vessel and set it aside.
Reserve this for your next batch of kombucha. This starter tea + SCOBY combo will be
what you use to make a future batch of kombucha!
You can keep it in a SCOBY hotel for future use. Or just put it temporarily in a
spare bowl if you plan to use it immediately to make your next batch of
3. This is super important: Stir the remaining kombucha in the brewing vessel.
The stirring will distribute the yeast and bacteria throughout the liquid. This’ll
help make your carbonation more consistent across all your bottles.
5. Dry the tops of the bottles and make sure the lids are dry
6. Seal tightly! If your bottles have screw-on lids, I like
to use rubber grippers to make sure they’re sealed as
tight as possible.
7. Let them ferment for another 2-3 days at room
temperature. I like to put them in a dark cupboard for this.
There’s a slight risk for over-carbonation and explosions if
the glass bottles are poor quality and/or your fruit purees
are really aggressive. Just to be safe, I like to keep them in a
closed cabinet to contain any mess.
Read my recommendations on choosing good-quality bottles
Note: Beer bottles are usually made of thin glass so if you opt to use them, I don't recommend leaving them at room temp. for longer than 1 day before moving to the fridge. This will minimize the risk for glass breakage. Or don't use beer bottles at all!
8. After a couple days at room temperature, move them to the fridge. Once they're chilled, open one to test it out. The cold will help keep the carbon dioxide in the liquid, so it’s less likely to fizz over and make a mess when you open it. The longer you F2 in the bottle at room temp, the more carbonation builds up, so be sure to move them to the fridge after a couple days to pause the fermentation process and prevent over-carbonation.
Should I burp my bottles?
I know a lot of home brewers recommend it, but I don't. I find it unnecessary and counter-productive to the fermentation process. You can read more details here. Instead, I recommend leaving them alone for 2-3 days, then moving them to the fridge. When they're totally chilled, that's when you should test one for carbonation levels.
What if it's not fizzy enough?
If you want more carbonation, you can bring the whole batch of bottles back out to room temperature and let them continue fermenting for another day or so. Then chill and test another bottle to see if the carbonation levels are better.
I’ve had some flavors get perfectly fizzy in 3 days, and I’ve had other flavors that needed a full week before they got to the carbonation level I wanted. It just depends! The temperature, flavorings, bottle, etc. all affect the timing here.
It takes some trial and error since your kombucha will be unique to you and your circumstances. But you can figure out what flavors you love and how fizzy you like it. And as you get the hang of it, you'll find a timeline that works best for you!
*On this page, you’ll find some affiliate links to sources where I’ve purchased my ingredients/materials that I use. I may get a small cut of Amazon's profit for finding + recommending them to you. It won't cost you any more than you’d normally pay for them. I went through a lot of trial and error to find low-cost, high-quality options to save us all money. But otherwise, feel free to purchase from wherever you like!