Warm Weather SCOBY Care: Brewing Kombucha in Hot Weather
A kombucha SCOBY (Symbiotic Colony Of Bacteria and Yeast) likes a bit of heat. The microorganisms in the culture reproduce quickly and thrive at a steady temperature of between 75F and 80F, which is warmer than room temperature. However, even at room temperature (65F-75F) the SCOBY will still be happy, so you don’t have to worry about turning up the heat in your house just to brew your kombucha. However, if the temperature drops below 65F, you need to find a way to keep your kombucha culture warm.
In the summer, many people have the opposite problem. While the SCOBY will do well at temperatures up to 85F, you’ll end up having problems with the long-term health of the culture if the heat stays higher than that for too long. Higher temperatures also mean quicker fermentation, which will change the quality and flavor of the finished kombucha tea.
NOTE: In this article, “temperature” means that actual temperature of the kombucha liquid and the SCOBY, not the ambient air temperature.
High Temperatures Affect Yeast/Bacteria Balance
A healthy SCOBY contains a balanced mix of yeast microorganisms and bacteria. The yeasts process the sugar into ethanol (alcohol) and CO2, and the bacteria take the alcohol molecules and convert them into the organic acids that contribute to the health benefits of kombucha.
When the weather gets warmer, the yeast become more active, and the bacteria may not be able to keep up with them. The bacteria will begin to die off when the temperature gets much above 100F. The yeasts in the SCOBY can survive at temperatures up to about 115F, but if you have all yeast and no bacteria, you won’t end up with healthy kombucha tea.
When there is more ethanol in the kombucha tea, the flavor will change and the fermentation will speed up. Some people deliberately increase the temperature of their brew in order to make kombucha wine but if this isn’t your goal, you’ll need to keep the temperature lower than 85F.
You can still brew Kombucha at 90F or even 95, but the ferment will happen much more rapidly and the flavor won’t be as subtle or as mellow as a lower-temperature fermented Kombucha.
We recommend you check out our article about How Temperature Affects Kombucha Flavor.
How to Slow Down the Yeast Activity in Warm Weather
One way to counter fast fermentation in warm weather (due to the yeast becoming more active) is to adjust the yeast levels in the brew.
Use Stronger Starter
You can slow down the growth of the yeast by adding more acid to your starter liquid. Instead of using kombucha tea from your previous batch as a starter, use distilled white vinegar instead. Be sure to use the correct ratio of kombucha ingredients when making the substitution.
Use Whiter SCOBYS
Another thing that will help maintain the balance is to use a SCOBY that already has the correct proportion of yeast to bacteria. A healthy SCOBY comes in a range of shapes, textures, and colors, but in general the darker the SCOBY the more yeasts there are. When you look at a SCOBY and see clumps or strings of brown material clinging to the bottom, those are yeast colonies. You can start your batch with LESS yeast by simply using a SCOBY that contains less yeast.
Choose the firmest, whitest, cleanest SCOBY in your SCOBY hotel to avoid overpopulating your brew with more yeast.
Use Green Tea
Another way to possible slow down fermentation activity is to use a different tea or tea blend. If you have been using Black Tea, try Green Tea or White Tea. The change of tea types may reduce the fermentation activity slightly.
Even if you are using a white SCOBY and an acidic starter, your yeast may still be more active due to the heat. More active yeast also means more active bacteria, as long as there are enough of the bacteria to keep up with the byproducts that the yeasts are producing. If you notice that the kombucha brew is only taking three to four days to become completely sour, then the fermentation process is probably going too quickly.
Faster Fermentation Means Fewer Nutrients
The beneficial acids and probiotic nutrients in kombucha tea are created by the action of the yeasts and bacteria working together. The longer they have to process the sweetened tea mixture, the more of these compounds are created. If your kombucha tea gets sour too quickly, you’ll have to stop the fermentation cycle before all of the nutrients in the tea are available.
How to Increase Nutrients in Faster Ferments
One way to increase the nutrients in the finished tea is to provide the yeast with enough food to start with, or changing up the type of ingredients which may slow down the yeast or increase the bacterial activity.
1. Add More Sugar
In warmer weather, the yeast is more active and will go through sugar more quickly. If you’re doing everything you can to keep the temperature low, and you’re still getting fast fermentation, add more sugar to the sweetened tea mixture.
2. Use Different Tea Types
You can also adjust the type of tea you’re using. This may have an effect on the yeast and the bacteria activity. Typically, Kombucha likes Black Tea the best and will ferment the fastest in Black Tea. Experiment with brewing green tea instead of black tea, or using a mixture of green and black teas, which may slow down the fermentation — something you want if it’s warm weather.
Warm-Weather Insects Can Be A Problem
In many parts of the country, summertime means ants in the kitchen. Ants like sweet things, and the sweet tea mixture your SCOBY is sitting on is going to be a target unless you protect your brewing jar.
First, make sure that your brewing container is covered with a tightly-woven cloth that is securely tied around the container opening. Don’t leave any wrinkles or openings where ants and other bugs can get in. Second, keep your brewing container away from places where ants are commonly found, like on the floor or on countertops where there are frequently crumbs or spills.
You can protect the brewing container and keep it cooler at the same time by putting it in a pantry or cupboard, or by putting it in a cold-water bath (see below).
Fruit flies are another problem in the kitchen, but they will not be able to get into your brewing container if it is tightly closed with a cloth and a rubber band or twine. Don’t use store-bought cheesecloth for the covering, because the mesh weave is much too wide. You can use muslin cheesecloth designed for use in dairies or by professional chefs, which is of a much finer weave. Or you can make a Kombucha Fruit Fly Trap.
Fruit flies and ants are attracted to spoiled or overripe fruits and vegetables, so keep your kitchen free of these items. They are also attracted to garbage, especially when it starts to ferment in the heat. Keeping a clean kitchen will help you maintain the quality of your kombucha and the health of your SCOBY – and it’s good for your health, too.
If you do have fruit flies in your kitchen, you can make a simple trap by pouring a little sweetened kombucha into a saucer and adding a squeeze of dishwashing liquid. The fruit flies will be attracted to the sweet tea and killed by the soap when they land on the surface of the liquid.
NOTE: If you do get ants or fruit flies inside your brewing jar, it’s a good idea to dump it out and start over with a new batch. You can rinse the SCOBY off with distilled vinegar if it hasn’t been damaged, but if you suspect that the fruit flies may have laid eggs in the SCOBY, throw that away too.
Ways to Keep Your Kombucha Cool
We’ve looked at ways to modify the ingredients and the ratio of yeast to bacteria to reduce fermentation activity, which can help in warm temperatures by slowing down the fermentation time.
However, you’ll also want to look at specific ways to REDUCE the room temperature where you brew. Here are some tips on how to do this. Ideally, you’ll want to use BOTH strategies to get the best Kombucha, especially if you are forced to deal with 90+ degree temperatures; one strategy may not be enough.
The Ideal Brewing Temperature
You will need to keep the liquid in the brewing container between 70F and 80F during the entire primary fermentation period, which generally takes at least 7 days. Because warmer temperatures speed up the fermentation process, you will probably not get the longer fermentation times you’re used to in the winter, when the lower temperature extends the primary fermentation up to 30 days or longer.
The temperature of the kombucha is what’s important, not the temperature of the air in the room. To get the best control over the brewing temperature, it’s worthwhile to invest in a digital thermometer with an immersible probe. You can measure the temperature of the kombucha without disturbing the SCOBY or moving the jar, by leaving the probe in the liquid and reading the scale display on the body of the thermometer.
Keep the Container Dark
Even the small amount of heat put out by a light bulb is doing its part to raise the temperature in the room. If you can put the brewing container in a place without light, it will be cooler. You can put your kombucha in the pantry, in an unused spare room, or in the basement (if you have one). The basement will usually be significantly cooler than the upstairs rooms in the first place, but a pantry with good ventilation can also be a good place to keep the kombucha brewing container. In some older homes, the pantry was designed with a window for ventilation, because that was where things were stored in the days before refrigeration.
If you have a spare room or office space where the windows face north, you should be able to keep that room fairly cool by keeping the windows open, but covered with curtains or other material that blocks out the light.
If you have space in your garage and the garage stays cooler in the summer than the house, you can leave your kombucha brewing container in the garage as long as it is protected from ants and other insects as well as dust. Be sure to keep the brewing container away from things like paints, weedkiller, and other chemicals.
The kombucha needs a supply of oxygen, so don’t close the container up in a tightly-sealed space like an unused refrigerator, even if that area can be kept cool and dark.
Just Add Ice
You can’t add ice to the brewing container, but you can lower the temperature of the liquid in the container by using ice or frozen ice packs. Put ice cubes or frozen ice packs into zip-lock plastic bags and close them tightly, squeezing out the air. Wrap each bag in a clean towel or old t-shirt and use string to tie them around the sides of the brewing container. The towels will soak up any condensation and will also protect the jar from direct contact with the ice.
You can also use ice in combination with a picnic cooler or another large insulated container. If you can prop up the bags of ice against the side of the cooler so that they are not touching the brewing jar, then you don’t need to wrap them in towels. Set a disposable aluminum baking tin underneath the brewing jar and fill it halfway with cool water to help maintain the right temperature. Don’t completely close the cooler, so the SCOBY can continue to get the oxygen it needs.
Use Marble and Stone
A marble slab stays cool for a long time, which is why bakers often use them for rolling out butter-rich doughs. You can get a piece of marble at a tile store or specialty chef’s store (and if there’s a quarry in your area, see if you can get a cracked slab for free). Put the slab in the refrigerator or freezer overnight, and then in the morning place it under the brewing container. Since the outside temperature generally cools off by at least a few degrees at night, you should be able to put the slab back in the refrigerator at the end of the day, and take it out in the morning when the temperature starts rising again.
You can also use stoneware crocks for your brewing containers. These thick opaque containers don’t heat up as quickly, even in the summer, and because they don’t let any light in, the liquid inside stays cooler. This is a good choice if you are setting up a continuous brewing system but stoneware crocks and pickling jars work very well for single-batch kombucha as well.
Natural and Artificial Air Conditioning
If you already use an air conditioner in your house or apartment, you’ll have less of a problem keeping your kombucha cool. Remember that what’s refreshing to you isn’t always what the SCOBY likes, and avoid the temptation to turn the thermostat down below 65F.
Moving air through a room, even if it’s not artificially cooled, does lower the temperature. A rotating fan will help cool the space, as will cross-breezes from open windows, even if the outside temperature is high.
If you live in the country, and happen to have a spring going through your property, you can put your brewing container next to the spring, in the shade. The cooler air over the water will lower the temperature. You can get almost the same effect by putting the container next to a fountain, though you’ll still have to make sure that it’s in the shade, and that it’s not going to be splashed by the water.
If you want some more tips on brewing in warm weather, read our other article: brewing Kombucha in Very High Temperatures.