How to Brew Kombucha
Brewing kombucha is similar in many ways to brewing beer (a sugar source is fermented) with the main difference being the microbes used to ferment. With beer, fermentation is completed by brewer’s yeast, whereas with kombucha, fermentation is completed by a symbiotic culture of bacteria and yeast (SCOBY).
View the How to Brew Kombucha video here.
These instructions were made brewing in the Small BREWHA Kombucha Brewing System, but these steps we use can be copied with the larger systems as well. The recipe is on the recipe page of our website. While these are delicious recipes in their own right, variations on ingredients can certainly be made.
Heat Water
The first step is to bring the water to boil. The BREWHA system includes a high quality stainless steel immersion heater, temperature sensor, and with all but the 120V Small system, a power controller to heat the water with. Boiling the water kills any microbes and also sanitizes the inside of the fermenter so that when fermentation starts, it is just the microbes you add that ferment (not any wild yeasts or bacteria or molds that might spoil).
The lid can be installed when heating, just ensure that a port is removed so air/steam can vent (and always have the pressure/vacuum relief installed and test it regularly to ensure it is working as designed). The hop basket is placed inside the fermenter so that it is sanitized at the same time.
Any good tasting, quality water can be used. Don’t use distilled water as some minerals like calcium are beneficial to fermentation so should be in the water. If RO or distilled water is used, brewing salts can be added back in; there is an introductory article on water chemistry on our website which discusses more.
Turn the controller on and start heating the water. Once the water is hot and will readily dissolve sugar, pause the heater and add the sugar in. Sugar shouldn’t just be dumped in because it will drop to the bottom undissolved. It can be added to the hop basket where it can be stirred and dissolved, or some hot water can be removed to a pot with the sugar, dissolved there, and then added back to the fermenter. If stirring inside the fermenter itself, just be careful not to hit the heating element or senser. Remove a little water out the bottom port to see if any solid sugar is there, and return that into the hop basket. Turning the heaters off during this addition minimizes the risk of sugar sticking to the heater and scorching. Once sugar is dissolved, replace the lid, turn the power back on and continue to heat it up.
Boiling
Once up to boil, the power can be turned down a little and the sugar water boiled for 15 minutes. The boiling water sanitizes the tank, and the steam produced here will sanitize the lid. Flush a bit of boiling water through the side and bottom ports to ensure cold water is not trapped there and the ports are sanitized, and rinse the outside ports off after with a StarSan solution so microbes don’t start to grow on any sugar residuals. The pressure gauge can be held part way over the venting steam for a minute so it is sanitized, and/or spray it with a sanitizer like StarSan. (Keep the water jacket empty during heat-up and boil.)
Cool Water
At the end of the boil, turn the heater off and add tea. Adding to the just-boiled water will sanitize the ingredients. The spoon or mixer used to stir the additions should be kept on a sanitized surface as we will use it later to stir the cooled water.
After a short period, remove the hop basket, return the lid (as mentioned, keep a port open and always leave the pressure/vacuum relief installed) and attach a cold water source (tap water) to the jacket. Use a water pressure regulator on the inlet port of the jacket to ensure pressure does not build up and damage the tank. It will take about 20-30 minutes for cold tap water to cool the water down to room temperature. Cooling time is dependent on the temperature and flow rate of cold water and the volume of water being chilled (relative to surface area). So for this small tank, cool down is about 20-30 minutes. For our larger tanks it will be longer so for faster cooling, one of our plate chillers (either with tap water if its cold, or pre-chilled water from our Cold Liquor tank) can be used; there is a video on our website called ‘Installation and use of the plate chiller with the BREWHA fermenter’ that discusses how to do this.
Add (or ‘pitch’) the SCOBY
Once the water is down to room temperature (20C/70F) stir it with the sanitized spoon (or mixer. This serves to equalize the temperature as well as introducing a bit of oxygen. In the larger tanks, after removing any sediment that settled to the bottom port, oxygen can be bubbled up into the wort to equilibrate the temperature. When using an aeration stone, it can be put it in boiling water for a few minutes to ensure it is sanitary.
Once the temperature is uniform, add the SCOBY according to supplier instructions. In our case, we will be adding about 10% by volume Kombucha from a previous batch. This will inoculate our tea with the SCOBY as well as dropping the pH a little (making it more acidic) to help minimize the risk of harmful microbes (like molds) getting established.
Fermentation
Once the SCOBY is added, we put a gas permeable covering over one of the openings. We want to keep flies and dust out (which might carry harmful microbes) but let air (oxygen) in. We are using a coffee filter, but tight woven cloth also works. Unlike beer production where oxygen is only needed early in fermentation, and harmful (for flavor) later in fermentation, oxygen is necessary throughout fermentation when making Kombucha.
With the 208-240V systems, temperature can be maintained through fermentation by setting the temperature setpoint and keeping the heaters on ‘auto’. If fermenting above room temperature, put the power output to less than 3% so that the heating is very gentle and there isn’t any risk of scorching.
Carbonation
To know if your beverage is ready for consumption, fermentation can be tracked by monitoring the amount of sugar (using a hydrometer or refractometer and comparing the amount of sugar to the amount at the beginning; as yeast consume sugar they produce CO2 and ethanol so less sugar means more CO2 and ethanol). And with SCOBY, fermentation progress can also be tracked by measuring the pH (using a pH meter is the most accurate), as bacteria consumes ethanol it produces acids which lowers the pH; acidity below 3.5 is the target, and below that, according to taste.
Once you have determined that the kombucha has completed fermentation, the pellicle can be removed (the floating cellulose ‘puck’ or ‘mother’), and the kombucha carbonated. Carbonation can occur by adding a bit more sugar (sanitize the sugar by dissolving in boiling water before adding it to the fermenter) and letting the Kombucha carbonate naturally as the yeast feed on the new sugar and produce CO2. Or a regulator and CO2 tank can be used and to add carbonation. In a commercial setting, there will CO2 tanks and commercial regulators to add CO2. For pilot systems or home brewing, there are mini regulators on the market that use mini gas tanks such as the blue CO2 bottles by Soda Stream and their competitors. There are carbonation gas charts on our website, but the level of carbonation depends on your tastes. For kombucha stored at 20C/70F, a low level carbonation typical for kombucha will need about 8psi of CO2 for 3-4 days. A higher level for higher carbonation.
(Tip: For faster carbonation with gas, purge the head space a few times to remove the air—Nitrogen/oxygen etc.—so that more CO2 is present, or bubble CO2 in through the racking arm. If putting gas in below the water level, be aware that the beverage doesn’t infiltrate back into your gas line which will contaminate it, so either use a check valve and/or run the gas line above the water level so if the beverage enters, it doesn’t reach the regulator, and clean out the line or replace it.
If adding a flavoring, if not added to the tea at the beginning they can be added now. Whatever you add, ensure it does not have synthetics or oils that might harm the microbes.
Storage and Serving
To help preserve the high quality state of your beverage, it should be stored at or around fridge temperature. Our water chillers can be used to run ice cold water through the jacket of the fermenter to lower the temperature. (Note that since more CO2 can dissolve in water at lower temperature, the gas pressure should be lower for a given carbonation volume—search for ‘how to carbonate in the BREWHA fermenter’ on our website for more information).
Once chilled and carbonated, it is ready for serving! Can it, keg it, or connect it to one of our dispensers for direct serving from the tank—and enjoy it! (For kombucha, remember to keep 10% for inoculating your next batch – this can be done by keeping the racking arm pointing up – the volume from the top of the racking arm to the bottom of the cone is approximately 10%. With the racking arm pointing up, when the kombucha ‘runs dry’ the remaining kombucha can be removed out the bottom port (sanitize the exterior first; I hold a pot of just-boiled water over the port for a minute, and then spray with Star San) and put in prepped second fermenter with tea, or held in a sanitized holding vessel until ready to pitch.