How to Lower Bacteria Populations in Kombucha
Is your Kombucha SCOBY bacteria dominated and low on yeasts? If so look no further, because in this post we go through what you can do to tone down the bacteria and encourage to yeasts so that your SCOBY can come back into balance.
Kombucha is fermented by a combination of yeasts and bacteria. They make up the SCOBY which stands for ‘symbiotic colony of yeasts and bacteria’. While the two populations are in symbiosis – and work together – they are at the same time mildly in competition.
If conditions are such as what the bacteria like, they can become dominant and the yeasts can fall into decline. The SCOBY is then out of balance and some brewing hassles can ensue. Usually it is the yeasts which get out of hand, particulary in warmer climates. However there are instances where the yeast populations decline, and the bacteria have the upper hand.
If this is the situation with your ferment, then there are some steps you can take to bring your kombucha culture back into balance.
But before we get into that lets just take a quick look at why having a balanced culture is so important.
Why Having a Balanced SCOBY Culture is Important
Because the yeasts and bacteria in the SCOBY are involved in a symbiotic relationship they need each other in order for successful fermentation to take place.
How the Yeasts and the Bacteria Work Together
The yeasts work to convert the sugar in your sweet tea. From the sugar they produce alcohol and carbon dioxide. The alcohol in turn serves as the food source for the bacteria. They eat up the alcohol, and produce natural acids. These acids are very healthy to drink, and are what gives kombucha its signature tartness. The yeasts convert away sugar, feed the bacteria and also make the kombucha fizzy with the carbon dioxide they produce.
What Happens When There Are too Many Bacteria and Not Enough Yeasts
When cultures are dominated by bacteria and have very low levels of yeasts present – the following can occur:
- Very low levels of carbonation
- Very slow ferments
- Ferments which stall
- Batches which do not want to ferment at all
None of these are things you want to have happen to your brewing kombucha! They can result in endless brewing hiccups and frustrations. So! Let’s take a look at what you can do to bring your kombucha SCOBY back into balance by decreasing the bacteria and encouraging the yeasts.
5 Ways to Decrease Bacteria Populations in Kombucha
The key to bringing your SCOBY back into balance is to create the right conditions. These have to be such so that the bacteria and the yeasts are both happy and neither outcompete the other. This is pretty simple once you get the hang of it.
# 1 Increasing the Brewing Temperature
This is the most important thing to look at when balancing your kombucha culture. Kombucha can be easily brewed within a temperature range of 68 to 84 degrees Fahrenheit (21 to 29 degrees Celsius). However, the yeasts and the bacteria prefer different parts of this temperature range.
The yeasts like the warmer half of this range, and the bacteria prefer the cooler half. A common cause of SCOBY imbalances is brewing temperature. In the case of overactive bacteria this is very likely due to a brewing temperature which is too low. If you live in a cool climate – and your kombucha brewing is at or below 69 F for extended periods, then you may have just discovered the cause of your problem.
Ways to Increase Brewing Temperature in Your Kombucha
Brewing in the Warmest Room
If you are brewing kombucha in low temperatures and wish to increase the brewing temperature of your batches the first thing to do is to look for the warmest location in your house. This can be tricky, as kombucha shouldn’t be placed in direct sunlight as it can be harmful to the SCOBY. So sunny window sills are out. You can however choose a spot in a sun filled room which is out of direct rays. Here the brew can still benefit from the warmth of the room, but won’t be harmed.
Warming Your Brew Artificially
If however you find that merely selecting a warm room as a brewing spot is not enough, you might have to turn to artificial means.
There are two concerns when it comes to artificially heating your kombucha. The first is to not overheat it. If you radically overheat your kombucha – you will cook it. If you mildly overheat it, then you will experience the brewing problems associated with overly high brewing temps.
The other consideration when artificially heating kombucha is not to apply heat unevenly. The temperature of the brewing kombucha should remain relatively constant, and be applied as evenly over the brewing vessel as possible.
Ways to Artificially Warm Your Brewing Kombucha
You can use the following items to warm up your kombucha:
An Electric Blanket
Electric blankets can work well for warming up kombucha. You can wrap up your brewing vessels in them, and apply the heat evenly. The only concern is not to set the heat too high, in case you damage your brew. If you find that the kombucha is getting too warm, you can move the blanket away from the jars, to form a sort of tent with an open top. This will warm the air around the jars.
Some people have reported success using hot plates to warm up their kombucha. The hot plate needs to be set at an extremely low setting. If your plate does not have very low settings, then avoid this method. Also, a hot plate only heats the kombucha from the bottom up, which can result in uneven heat distribution within the brew.
Make a Bath For Your Kombucha
An option which can work quite well is to create an even temperature ‘bath’ for your kombucha. You will need some large containers to hold water , and a heating element such as what you find in an electric kettle, and a temperature regulator. If you have the expertise to combine the element and the regulator together, then you will have yourself a highly effective and hands off kombucha warmer. By keeping the water at the right temperature for the kombucha to brew at, you can heat it evenly from all sides, and maintain the same temperature throughout the day and night with no adjusting needed on your part.
A Kombucha Heater
The best option is of course a kombucha heater! They are specially designed to keep kombucha at an optimum temperature, while giving it access to air and light. Kombucha heaters are an outlay, so they are most suitable if you experience a lot of cold weather for extended periods of time.
If you want some more tips and info on raising the brewing temperature of your kombucha, you can also check out Cool Weather SCOBY Care: Brewing Kombucha in Cold Weather and How to Brew Kombucha in Cold Weather.
Get a Thermometer
If you do not have one already, then purchase a thermometer which you can use to measure the temperature of your brewing kombucha. This is very important for getting everything set up to the point where the kombucha is brewing at an ideal temperature. A 75 to 85 degrees Fahrenheit (24 to 30 degrees Celsius) range is considered to be what the yeasts thrive in and what inhibits the bacteria.
# 2 Brew Strong Tea
Strong tea is advantageous to the yeasts. This is because it contains higher amounts of sterols. Sterols can be used by the yeasts for their reproduction process. The quicker the yeasts can multiply, the sooner your SCOBY culture will come back into balance.
How to Brew Strong Tea For Kombucha
Most black tea is usually brewed for between 3 – 5 minutes. Green tea is brewed for less. To make a strong batch of black tea, allow your bags or leaves to steep for up to 7 minutes. However, at this point remove them from the hot water, otherwise you may find that the excess of tannins spoils the flavor of your final kombucha.
(If you have been struggling with bitter kombucha, the take a look at What to Do if My Kombucha is Bitter)
# 3 Brew Black Tea
If you have been using green tea, or a mix of green and black tea – then switch back to all black for a few brews. The yeasts like the black tea, and thrive on its high level of tannins.
# 4 Take Starter Liquid From the Bottom
When setting up each new batch of kombucha, try to get the starter liquid from the very bottom of whichever container it is in. This is because free floating yeast strings and particles can often accumulate here. If you use this cloudy sediment filled starter liquid, you will be giving your kombucha an injection of additional yeasts right from the get go. Combined with tweaking any other conditions neccesary (such as temperature, tea and sugar) this can over a few brews bring your culture back into balance.
How to Take Starter Liquid from the Bottom
This is all well and good, but how do I get to the starter liquid aa the bottom? Well there are two main options.
If you have a syphon, or even a length of hose, you can use this to suck up starter liquid from the bottom of the container in which it is in. Syphons are of course the easiest, but a length of hose can also work fine.
The other option is to simply take a cup, and gently insert your hand and arm into the container in which the starter liquid is. Trying to disturb as little as possible, scoop up some of the bottom liquid with as much sediment as you can get.
# 5 Do Not Use Too Much Sugar
It is easy to suppose that to encourage the yeasts you can give them a little extra sugar, seeing as this is their food source. However, this can actually slow the yeasts down! If presented with too much sugar all at once, the yeasts can become sluggish and underactive. Much like we feel after an overly large meal. In the brewing world this is known as the ‘Crab Tree Effect’.
How Much Sugar to Use
Stick to the golden ratio of:
1 cup of sugar to 1 gallon of tea
If you feel that you want to feed the yeasts additional sugar, then rather do so in the middle of the brewing cycle. At this point they will have eaten up some of the sugar already present, and might be able to process a little more.
To make sure that the yeasts never slow down because of overeating, you can even reduce the amount of sugar you make the sweet tea with in the beginning, and feed this to them at the midway point.
Although it is unusual for the bacteria to dominate kombucha ferments – this can happen, especially in conditions where temperatures are low. For hassle free brewing it is always important to make sure that the yeasts and the bacteria within your SCOBY are in balance and are supporting each other.
A balanced SCOBY is most likely to yield consistently good kombucha, which matures at relatively the same rate, and has reliable levels of carbonation and natural acids.
By tweaking temperature, tea strength and type, sugar quantities and starter liquid, you should be able to get your culture into balance in no time at all.
Once the problem is fixed, it is still a good practice to whenever working with your kombucha gauge what proportion of yeasts there are to bacteria. Bacteria manifest themselves by making thick and fast growing, fat, SCOBY houses. Yeasts show up as long brown strings and particulate. For a balanced SCOBY you want to have good SCOBY growth, as well as a medium quantity of brown yeast strings. However you do not want the yeast strings to starting choking out the brew either, as that will cause its own set of problems.
When balancing the SCOBY it is important to do so in moderation. Do not make such drastic changes to temperature and ingredients that the SCOBY swings in the opposite direction and becomes yeast dominated.
If this does happen though, there is no need to worry. Simply get to work once more and apply the principles for reducing the yeasts and find the sweet spot between bacteria and yeasts.