How To Brew Kombucha In (Very) High Temperatures
It Gets Very Hot Where I Live – What Can I Do?
If you live in an area where it is very hot all year round, or where temperatures in the summer can get very hot, then you might be experiencing some problems with you kombucha brewing. It is not impossible to produce good ferments in warm temperatures, however there are some things you should know in order for you to care for your SCOBY culture, keep it in good condition, and get good fermentations.
Fermentation Temperature Ranges
Kombucha tea can be brewed within the temperature range of between 64o Fahrenheit (18o Celsius) and 86o Fahrenheit (30o Celsius).
Below 64 degrees, fermentation will slow to a halt because the yeasts and bacteria will start to go to sleep, or go into a state or dormancy. Above 95 degree, the bacteria will start to die off.
The Ideal Temperatures For Fermentation
The optimum range of temperatures, in which really good brews are easy to achieve and where one experiences the least problems, is between 69o Fahrenheit (22o Celsius) and 84o Fahrenheit (29o Celsius).
If you are brewing in the 69-71o Fahrenheit (21-22o Celsius) and 82-84o Fahrenheit (28-29o Celsius) range, then any problems you might be experiencing with your SCOBY culture or kombucha brews could be due to another cause (i.e. NOT the temperature).
If this is the case, then it might be a good idea to check out some of our other guides and posts about troubleshooting your SCOBY.
What Might Happen If You Brew in Warm Temperatures (Over 82o Fahrenheit / 28o Celsius)
If your fermentation is sitting above 82-84o Fahrenheit (28-29o Celsius), then you most probably will be experiencing some of the problems associated with warm weather brewing.
Here are the problems you may experience if the temperature is too warm:
1. You May Get Super Fast Ferments
In very warm temperatures, the fermentation process will usually speed up, and your brew of kombucha will start to take on a sour tang in under 7 days. Depending on the temperature,
fermentation will take between 7 and 30 days. If one leaves the brew for longer than 30 days, the SCOBY will start to run out of nutrients and begin to starve. If you are getting a vinegary smell and sour taste in under 7 days, and the temperatures are above 82-84o Fahrenheit (28-29o Celsius), then you need to try and cool down your brew.
The Effects of Fast Fermentation on Taste
Generally, fast fermentation time gives undesirable flavors. Slower fermentation times allows the flavor to develop gradually in stages, giving softer more subtle tastes. Faster ferments tend to give a stronger Kombucha flavor that’s more tart. It may also give a yeasty flavor, which most brewers find is undesirable.
Read our article about How Temperature Affects Kombucha Flavor for more information about it.
2. You May Get a SCOBY Imbalance
If fermentation temperatures get too high, the yeast component of the SCOBY can outnumber the bacteria population. This is because the yeasts can handle higher temperatures than the bacteria, and therefore will be on the rise, as the bacteria start to decline with the higher heat levels. A proliferation of the yeasts is actually the cause of the above scenario – super fast ferments. Because the bacteria are being out competed by the yeasts, this means that the yeasts sour the brew prematurely, before the bacteria can do their part.
Active yeasts in and of themselves are not a bad thing, as they support the bacteria. They do this by converting the sugar present into ethanol, which the bacteria use as food and as fuel. They in turn produce the organic acids which gives kombucha its wide range of health benefits. Now if the yeasts outnumber the bacteria and are more active, then this will result in them producing more ethanol than the bacteria can process. The higher ethanol gives that tart flavor in the Kombucha. The higher the ethanol, the more sour the Kombucha.
Thus too much ethanol means you’ll get a sour vinegary Kombucha.
Why Fast Ferments and SCOBY Imbalances Are Not Good
You might be thinking, well what the heck is ‘SCOBY balance’ and why wouldn’t I want my kombucha to ferment quickly? The quicker it ferments the sooner I can drink it! Well that is true, but fast ferments are not really ideal.
The longer kombucha is left to ferment, the more time the bacteria have to produce the organic acids. When the yeasts are on overdrive in high temperatures, and are prematurely souring the brew, the bacteria have not had a chance to do their bit, and the finished ferment will not be nearly as complex and beneficial in its makeup.
The more your ferment can be slowed down, the better the final flavour will be. An overly fast fermentation can also take on a yeasty taste.
The element of the over enthusiastic yeast population within the SCOBY (which is actually the underlying factor behind fast fermentations), is also not ideal. The overall health of the SCOBY culture is out of whack, and besides fermentation problems, you will also experience malformed SCOBYs. Overly fast ferments and over active yeasts are common if not inevitable in warm climates. However there are measures one can implement to keep one’s SCOBY in balance.
Why A Higher Yeast to Bacteria Ratio is Not Always Bad
Now, you may want a higher yeast population in a few certain situations:
a) You want to bump up the natural level of Alcohol present
Typically, raw Kombucha can half a range of alcohol percentage between .8 to 2 percent. Usually it’s about .8. But if you tinker with the yeast ratio so it’s higher, you can bump it up to 1 percent or more. If you do a second ferment and you have higher yeast levels, you may be able to get it up to 2 percent.
b) You want to make Kombucha Alcohol
If you are attempting to make kombucha wine, or a more alcoholic kombucha, then this is just what you want, as ethanol is alcohol. For step by step guides on how to do this, have a look at How To Increase Alcohol Content Of Kombucha Tea and How To Make Kombucha Alcohol.
c) You want a specific flavor that fast fermentation brings out
It could be you want a stronger Kombucha flavor. If this is the case, by all means go for a fast ferment!
d) You want to make Kombucha Vinegar or Tea Wine
If you want to make vinegar, well you can certainly achieve this by getting a sour brew. Keep in mind though, you can still achieve Kombucha vinegar by doing a slow ferment — you just have to let your kombucha ferment for a long period of time (3-4 weeks). A slow fermented Kombucha vinegar will have more beneficial organic acids than a fast fermented Kombucha vinegar.
However, if a fast ferment is not your objective, then you will want to try and manipulate things so that your fermentation process can continue, and so that the bacteria can make use of all of the ethanol which the yeasts are producing and in their turn generate the organic acids and vitamins.
What Happens if You Brew Kombucha in Super Hot Temperatures (95 degrees+)
It’s very difficult to make good Kombucha in high temperatures. The problem is that above 82 degrees (28 degrees centigrade), you start to get an imbalance with the yeast becoming far more active than the bacteria. This has the effect of a) the brew starts turn acidic before the bacteria has had enough time to create the beneficial organic acids and b) fermentation time is shortened, at the cost of being less nutritionally charged and c) the brew may take on a different, more yeasty flavor.
At above 95 degrees, the bacteria in Kombucha starts to die, leaving only the yeast. Thus, if you brew in weather too warm, you are more likely to brew ‘tea wine’ then kombucha.
If your brewing temperature is above 82 degrees, you should follow the guides below. If your brewing temperature is close to 95 degrees (or god forbid, 100+ degrees), then you absolutely should follow the advice below.
What To Do to Counter High Temperatures
If you are residing in a place where it is very warm all year round or the summers are very hot, it is a little more difficult to get the temperature of your kombucha down, than if you have the opposite problem and want to get it up. However there are a couple things you can do to counter high temperatures and lower the brewing temperature.
There are also some things which you can do to encourage the bacteria population within your SCOBY culture, and quieten down the yeasts a little. This should slow down the fermentation to a normal rate, resulting in better quality brews, and a more balanced culture, even if the brewing temperature remains high.
1. Find a Lower Temperature Location
If your fermentation is sitting above 82-84o Fahrenheit (28-29o Celsius), the first thing which you should do is hunt around your house for the coolest place possible. Remember this place should be clean and free of rampant bug life. Try and think of cool places, such in a room at the back of the house where the sun does not shine in, or in low cupboards where the vessel/s can perhaps stand on a stone floor. Granite counter tops retain coolness, so if your kitchen has these as counter surfaces, this might indeed be the coolest place.
Darkness will slow down fermentation, and if the temperature is not very warm, cause your culture to go to sleep. However if the temperatures are very high, a location with less light should not be a problem. In fact it might help to slow your ferment a bit!
2. Create a Lower Temperature
If you just cannot get a spot within your house which will be cool enough for your kombucha brew, then you will have to implement a system to cool it down. People do various things depending on what they have on hand, but here are a couple simple ideas.
- Ice and Cooler Box
Freeze some ice packs, or if you don’t have ice packs merely fill some plastic bottles with water and freeze those. Take a medium to large cooler box (having enough room is important as the ice must not touch the brewing vessel) and place your brewing kombucha in it. Now place the frozen ice packs or water bottles around the sides, taking care not to let them touch the brewing vessel. Place the lid of the ice box on askew. Make sure that you do not seal it, as the kombucha and SCOBY need air flow.
- Cooled Stone Slab
Bakers use cooled stone slabs to roll out rich pastry. This trick can work quite well for getting the temperature of your kombucha down. Get your hands on a stone slab. Once obtained, leave it in the fridge overnight. Let your brew sit on top of this during the day time, then cool the slab down over night again. This should allow for an even temperature, as usually the air temperature will drop a couple degrees at night, even in coastal areas.
3. Slow Down The Yeasts
By slowing down the yeasts, we mean using some strategies to reduce the yeast population at the start, or hindering their growth during the fermentation.
Slowing down the yeasts will ultimately slow down the fermentation process. In conjunction with a slightly lower temperature point above, you should then experience brews which ferment within the normal time frames and are mature and high in organic acids and vitamins.
By reducing the yeast population from the start, you allow the bacteria to get more of a foothold and create the organic acids. Note that by slowing down the yeasts, you may end up with ferments that take longer than normal (in some cases, up to twice as long).
1. Used Aged Starter Liquid or Vinegar
To inhibit the yeasts use extra sour starter liquid (i.e. aged starter) or distilled vinegar. The reason is that most of the yeast will have died off in aged starter. In distilled vinegar, there is no yeast at all.
You are essentially starting the brew with ‘less’ yeast in the sweet tea mix than you normally would have.
A good place to get really mature starter liquid would be from your SCOBY hotel (for directions on how to start and care for a SCOBY hotel check out How to Create a Kombucha SCOBY Hotel). Be sure to take liquid from the top of the storage vessel, as this will contain fewer free floating yeasts.
2. Make Kombucha with the Whitest SCOBY You Can Find
White SCOBYS have less yeast than yellow/brown ones. Brewing your Buch with a white SCOBY means you start off the brewing process with LESS yeast than you would with a darker SCOBY. Less yeast means the bacterial populations will gain more time and release more organic acids before the brew starts to ‘ferment’ and turn acidic.
Basically, you are slowing down the fermentation time and giving the bacteria more time.
How to Get a White SCOBY:
- Young SCOBYS are less likely to have higher ratios of yeast. So use a young (the youngest) scoby you can find.
- SCOBYs brewed in Green Tea tend to be whiter.
3. Use a Brewing Vessel with a Larger Surface Area
You can also change to a brewing vessel with a larger surface area. This will enable larger bacteria populations to develop quickly, and by doing so help to maintain the culture’s balance.
4. Brew With Weaker Tea
Another trick you can do is to brew with weaker tea. The stronger the tea, the more sterols the yeast will have (sterols are what yeasts consume to reproduce). If you don’t provide the yeast enough sterols, they will create their own. This takes more time for the yeast which slows down their reproduction allowing the bacteria to reproduce faster.
You can brew with weaker tea by:
- Steeping for less time. Steep black tea for under 10 minutes and Green tea no longer than five minutes. OR.
- Use less tea. Reduce the amount of tea you brew with. Reduce the tea amount slightly by about 20 or 30 percent.
5. Mix in Glucose
Another method you can use is not to restrict the yeast grown, but increase the Bacterial growth right from the start. The way you can do this is to replace some of the sugar with pure glucose, which the bacteria can more easily feed on. Add in 1/7 of a cup of glucose (Karo brand works) with the other 6/7 of a cup regular sugar per gallon of tea.
According to studies, regardless of what the temperature is, the majority of the acids, which are really beneficial for us are not produced in good amounts until a week has passed. So besides ensuring better SCOBY health and a balanced culture, cooling and slowing down the culture will ensure that you are getting optimum benefits from your batches of kombucha. If you want to read more about brewing kombucha in hot weather, you can also read Warm Weather SCOBY Care: Brewing Kombucha in Hot Weather.