Basic Guide For Second Fermentation
The second fermentation (or F2 for short) adds flavour to your kombucha and is the step where you can get really creative. However there are a few things to consider, flavour wise but especially security wise (not joking). In this step you will bottle the kombucha together with flavour giving ingredients. This will give the brew flavour but also infuse carbonation into the drink. The amount and type of ingredients you use directly correlate with how much carbonation will be generated. If you let the filled bottles sit too long (the carbonation gets too strong) the bottle can explode! How much pressure a bottle can hold highly depends on the quality of the bottles you choose!
Bottles
Bottles are the key feature of the second fermentation. They have to be airtight so the carbonation gets forced into your brew as it cannot escape the bottle into the air. This on the other hand puts a lot of stress onto the bottle, as the carbonation will build up quite a lot of pressure. Good quality bottles are key to a good and save brewing experience and are not that expensive. Also you will be able to reuse them for years. Do not skip out on buying quality bottles.
Types
Personally I always used swing top bottles for brewing. As adding and removing fruits from a bottle can be a pain with normal ones, I bought myself bottles with a wider neck.
If you go and by bottles, do by round ones. They can hold the most pressure, while square ones will burst way earlier. Do not buy fancy bottles made for decoration. And do not buy the cheapest bottles that you can find. While in general there is nothing wrong with cheap bottles, they are usually not made for that purpose. A good example are IKEA bottles. They are cheap and good for everyday usage, though not for brewing.
A very cheap and save option would be swing top bottles used for brewing. Those usually have the downside that they are colored so you cannot see what goes on inside of it. However they are a great option for first time brewers who want to try out this fermentation before investing a lot of money into equipment.
Sizes
The size of the bottles in general is up to you as long as they can hold the pressure of course. So a 3l bottle will most likely be no option. Personally I like 0.5l bottles the most however I do have some other sizes as well:
- 0.25l bottles: for experimenting with new recipes and ingredients
- 0.5l bottles: for everyday brews and more explosive recipes
- 1l bottles: for all time favourite recipes
Note that the carbonation will get less after you opened a bottle (as with coke or any other carbonated drink). Drinking from a 1l bottle over 5 days will leave you with a stale brew. Using two 0.5l bottles might be the better option in that case.
Preparations
Clean Bottles
This should be obvious, but I’ll state it anyways. Before starting a second fermentation, clean your bottles. You do not have to use products during this process, but use a bottle washer to get rid of any rest content of the last brew, especially the yeast on the bottom of the bottles. If you use products, make sure that you wash it out with water afterwards.
If your bottles have a remove able seal, make sure that there are no residues under it.
Reserve New Starter Liquid
As described in the First Fermentation Guide you have to reserve some F1 kombucha for your next batch. If you reuse the same vessel, put 1/5 of its content aside. If you forget this step, you can use some starter liquid of a Scoby hotel if your have one, or ask another friend to five you some once his next batch is done. Do not use vinegar instead of starter liquid, or your kombucha Scoby might turn into a vinegar Scoby.
Get Ingredients
TODO frozen stuff ok. If you have too much of something, freeze it for later! (smoothies work great!) -> possible to prepare ingredients in advance!
Bottling Or Second Fermentation
In the second fermentation you bottle your F1 kombucha and add other ingredients, such as herbs, spices and fruits, to your brew. The bottles will rest at room temperature for 3-4 days within the airtight bottles to trap the produced carbonation inside the kombucha to result in a fizzy drink.
Ingredients And Recipes
The possible combination of ingredients is basically endless. However some of them have to be used with care.
Some ingredients can only be used in very small doses. Dried lavender flowers for example have a very intense flavour, even when only using 0.1g in half a litre bottle. Some ingredients, especially exotic fruits, might reveal a lot of unwanted taste due to chemicals used during transport. As an example I had a very intense sulfur taste when using a mango for my brew. I stopped buying whole fruits and started getting frozen ones.
Other ingredients on the other hand are quite explosive. Keep your hands of anything that contains oils and fats at the beginning (coca, coconut, nuts,..) and test them in very small quantities before adding more. Hop and ginger are also examples for very a potent carbonation.
It does make sense to write down notes about the tested ingredients, flavour wise as well as carbonation wise but most of all it is necessary to be able to reproduce your brews. I just hate to figure out a recipe that I really really like, just to find out a month later that I did not write it down and just cannot remember it. It’s the main reason why I started to write down general recipes and started this blog. Note: all recipes are for 0.5l bottles.
Sugar
If you are using fruits with a lot of sugar content, you do not need sugar at all. Otherwise I usually add 1 tsp of sugar (3.5g) into a 0.5l bottle. This will add some sweetness but also help the carbonation a lot. If you do not want to add more sugar, you don’t have too, however I encourage you to compare the sugar content of any other drink you buy to this one. Fruit juices usually have between 10 and 14 percent sugar content, at least most better quality organic ones here in Austria. Compared to that 3.5g additional suggar for 0.5l of kombucha is pretty much nothing.
Burping
When burping, you release some pressure from the bottle by opening it a short amount of time. Depending on the temperature and especially the type and amount of ingredients you choosed you should burp the bottles up to once a day. If you have to burp it more often, you should definitive change your recipe (doubled ginger-hop recipe, Im looking at you!).
At the beginning I would suggest to burp once a day until you get more comfortable with the process, your bottles and your recipes. If you do not know how to burp properly, check youtube! If you still are not sure, try it in the shower. If done wrong this can make a hell of a mess.
I usually do not burp the last 24 hours before cooling the brew down, except Im dealing with an explosive recipe.
Cooling
This is one of the most essential steps and especially hard for beginners. Cool down your brews before opening them up fully! The cooler the kombucha, the less carbonation can escape from the bottle. While during burping a lot of carbonation escapes from the fluid (the white cloud raising up the bottle), cooling down the brew prevents that from happening and you will end up with a very carbonated fizzy drink. Opening an un-burped un-cooled bottle will look pretty similar to putting mentos in coke.