How to Decrease Yeast Population in Kombucha
Do your kombucha yeasts look like they are out of control? In this post we take a look at what characterizes a yeast overgrowth, and just what you need to do to get the yeasts back into balance.
Kombucha’s microbial populations are made up of yeasts and bacteria. Maintaining the balance between these two colonies is very important. A balanced batch of kombucha will brew without issues, and yield up great tasting kombucha which has a deep flavor profile and good levels of carbonation.
While it is possible for the bacteria to sometimes gain the upper hand, what is more common is that the yeasts start to dominate.
How to Know If Your Kombucha Has a High Yeast Population
Fortunately it is really easy to know if you have a lot of yeast in your brewing kombucha. Yeasts show up as long brown strings. These are easily seen, either lightly attached to the SCOBY, or floating freely. Silt and particulate is also usually made up of tiny bits of these yeast colonies, either broken off or busy forming.
So, a batch of kombucha which has a lot of yeast action going on will look like this: Lots of brown strings coming off of the SCOBY, or floating alone, and usually a lot of silt and particulate hanging out the at the bottom of the brewing vessel.
Sound familiar? If this is what you have in your brew, then it might be time for a yeast clean out.
If this sounds totally unfamiliar and you have never seen any of these strings or silt, then you might have critically low yeast levels instead. For info on how to bring yeast levels up, take a look at our post How to Increase Yeast Populations in Kombucha.
Characteristics of a Yeast Dominated Ferment
Besides being able to see the yeasts clearly in your brew, you might also notice the following brewing phenomenon/ problems:
- Overly fast ferments
- Too little carbonation
- A lot of carbonation
- Flat flavor profile
3 Ways to Decrease Yeast Population in Kombucha
If you have ascertained that you do indeed have a lot of yeast activity going on and they are dominating the ferment, then it is time to take some action. As you can see, yeast heavy ferments do not usually produce great kombucha. They also brew erratically. Thankfully there are a few sure fire measures which you can take to bring down the yeasts.
# 1 Lower the Brewing Temperature
The first thing to look at when planning on reducing the yeasts is the temperature at which it is brewing.
Kombucha can be brewed within a temperature range of 69-84 degrees. The yeasts like the upper range of these temperatures and the bacteria like the lower end. So, if your kombucha is brewing at a pretty warm temperature, this will cause the yeasts to proliferate over time and the bacteria to take a backseat.
If you want to balance the yeasts and the bacteria long term, lowering the brewing temperature will go a long towards maintaining this balance.
Here are a few quick ideas on how to reduce the brewing temperature of your fermenting kombucha.
For more info on cooling down kombucha, check out How To Brew Kombucha In (Very) High Temperatures and How to Counter Extreme Seasonal Temperatures for Perfect Kombucha Brewing.
How to Lower the Brewing Temperature of Your Kombucha
Finding a Cooler Place for Your Brewing Kombucha
If your kombucha is brewing in a fairly hot part/room of the house, then the first thing to try is moving it to the coolest place you can find in your home. This is usually at the back of the building, where the sun does not shine onto any walls. Rooms with stone or tile floors are usually pretty cool. Just make sure that the spot you choose is clean, well ventilated and free from dust and insects.
If you only need to lower the temperature slightly, then selecting a ‘cool spot’ for your fermentation vessel might do the trick completely.
Cooler Box + Ice Packs
However, if you are brewing in really hot temps and need to drop the brewing range by quite a few degrees, then you might need to take an emergency measure. At least for the hottest part of the year.
Here is a method which does not require any electricity, just some time spent every day or two to swop out the freezer packs.
- Freeze some cooler packs or plastic bottles of water.
- Place your kombucha into an icebox, along with the freezer packs/bottles. Make sure that these do not touch the brewing vessel.
- Place the lid on top, but leaving a crack for airflow.
You might want to have a double up the quantity of ice packs / water bottles. This way you can freeze half, while the others are cooling the box – and then switch out and repeat.
# 2 Strain Your Kombucha and Starter Liquid
Adjusting the brewing temperature is a measure which you can take to keep your SCOBY and kombucha in balance. Besides this you can also immediately do a bit of ‘manual’ balancing. Straining falls under this.
If you strain your kombucha and starter liquid, this means that all of the yeasty particulate will be filtered out. Which will reduce the overall amount of yeast present.
When to Strain Your Kombucha
You can strain your kombucha anytime. If you wish to reduce the yeasts this very red hot minute, you can strain your brew and put it back together to finish fermenting. If you do not feel like the hassle, you can wait until time to bottle or second ferment.
Drinking these extra yeasts is not unhealthy (in fact very healthy because they are also probiotics). However excessive amounts of yeasts can imbue finished kombucha with a bitter unpleasant tang.
The most important thing for making an impact with regards to reducing the yeasts in your SCOBY is to make sure that the starter liquid which you are going to set up your next batch with is strained /filtered.
How to Strain / Filter Your Kombucha
There are a couple ways you can filter your kombucha. Here are some ideas.
Coffee Filter and Pour Over Manual Coffee Maker
If you make small batches of kombucha and have a manual pour over coffee maker – then this method might be convenient for you.
Simply set up the coffee maker and a filter, over a container with a suitable mouth to hold the coffee maker. Pour your kombucha through. Discard the filter.
Sifter and Wide meshed Cloth
The is a very easy method, and suitable for big and small batches of kombucha.
Line a sieve with a piece of cloth, which has a wide mesh. Place this over a bowl or large jar, and pour the kombucha through. The cloth will catch most of the particulate. Once done you can then wash the cloth out.
Large Funnel and Wide meshed Cloth
Here you line a big funnel with a cloth and pour the kombucha though this. This is great for large batches, and for filtering directly into bottles or other narrow mouthed containers
For more info on filtering your kombucha you can also read these posts, How to Remove Particulate from Kombucha and How to Filter Your Kombucha to Remove Yeasty Stuff.
# 3 Remove Yeast Strings From Your SCOBY
Besides filtering your kombucha, you might also want to pull off any brown strings of yeasts which area attached to the SCOBY.
Simply take the SCOBY in your hand over the sink, and gently pull off whatever brown strings you can see. You can also wash your SCOBY if it is really covered in brown yeast matter. This however should only be a once off practice, as continual SCOBY washing can unbalance your SCOBY in the other direction and cause the yeast levels to drop too much.
Knowing how to reduce yeasts and keep them under control is a vital part of SCOBY balancing. Keeping your SCOBY balanced will mean hassle free brewing which gives really great tasting kombucha. In fact, the microbial balance between the yeasts and the bacteria within the kombucha is the core of keeping your culture happy and avoiding all the brewing problems which can crop up if the culture is out of balance.
So get those yeasts down!
Once you have controlled the yeast levels, keep an eye on your booch batches. Monitor the yeast levels and step in again if the yeasts start to overdevelop. If the opposite happens and they go into a decline (this can happen particularly if the weather changes and turns cold), then apply the yeast encouraging techniques outlined in How to Increase Yeast Populations in Kombucha.