Brew kombucha at home: SCOBY care and two-stage fermentation

Quick answer: Brewing kombucha at home involves fermenting sweetened tea with a SCOBY (Symbiotic Culture Of Bacteria and Yeast) in two stages: first for basic fermentation, then second for flavor and carbonation. Brewing at home costs a fraction of what store-bought kombucha does.

In the Pacific Northwest, where home food preservation is a common practice for many growers, brewing kombucha can offer a substantial cost saving. A gallon of homemade kombucha might cost you around $2 to $3 in ingredients, while store-bought options in cities like Portland or Seattle can easily run $4 to $5 for just sixteen ounces, a difference that adds up quickly over a year. This fermented tea, with its distinctive tangy flavor, is a rewarding project for those interested in food preservation, much like making sauerkraut or sourdough.

Brewing kombucha involves caring for the SCOBY (the symbiotic culture of bacteria and yeast), running a first fermentation of sweetened tea, and completing a second fermentation for flavor and carbonation.

Understanding the SCOBY and its environment

The SCOBY is a dense, rubbery disc that floats on top of the tea. This acronym stands for Symbiotic Culture Of Bacteria and Yeast, and it is responsible for transforming sweetened tea into the tangy, effervescent drink we know [1]. A healthy SCOBY is necessary for successful fermentation and thrives under specific conditions. For instance, maintaining a consistent temperature between 75°F and 85°F is ideal for optimal bacterial and yeast activity. Temperatures below 68°F can slow fermentation significantly, potentially leading to mold growth, while temperatures above 90°F can harm the SCOBY and produce off-flavors.

The SCOBY’s nutritional needs

Like any living culture, your SCOBY needs proper nutrition, primarily from sugar and tea. For a one-gallon batch, a common ratio is one cup of granulated sugar and four to six black tea bags, or about two tablespoons of loose-leaf tea [1]. The bacteria and yeast consume the sugar, converting it into various organic acids, ethanol, and carbon dioxide. The type of tea also matters; black tea is traditionally used, but green tea or a blend can also work, though they may alter the flavor profile and fermentation speed [4]. Using plain, unflavored tea is best, as oils from flavored teas can harm the SCOBY over time. The starting pH matters: get the sweet tea to 4.5 or below before you walk away from it, using enough starter tea to do so, and let it drop to 2.5–3.5 over the ferment. A batch that starts above 4.5 has no acid protection during the days when the culture is still getting going, which is exactly when mold takes hold.

• Maintain brewing temperature between 75°F and 85°F for optimal activity.
• Use one cup of granulated sugar per gallon of tea for proper SCOBY nutrition.
• Brew with four to six black tea bags or two tablespoons of loose-leaf tea per gallon.
• Ensure the initial pH is 4.5 or below to deter unwanted microbial growth.
• Avoid flavored teas, which can introduce oils detrimental to the SCOBY.

The first fermentation: getting started

The first fermentation transforms sweetened tea into raw kombucha. To begin, you will need a clean, one-gallon glass jar, a breathable cloth cover, and a rubber band. Cleaning your equipment thoroughly is important. Wash with hot water and a mild unscented soap and rinse well; you are not sterilizing as you would for canning, since residues from harsh cleaners will damage the culture. You can find detailed sterilization methods in resources like our guide on home canning 101. For a one-gallon batch, brew four to six bags of black tea in four cups of hot water for five to ten minutes. Remove the tea bags, then stir in one cup of granulated sugar until fully dissolved.

Combining ingredients and waiting

Once the sugar is dissolved, add cold, filtered water to bring the total volume to just under one gallon. It is critical that the tea mixture cools to room temperature, ideally below 90°F, before adding your SCOBY and one to two cups of starter tea from a previous batch. This starter tea lowers the pH of the new brew, providing an acidic environment that protects the SCOBY from undesirable microbes. Cover the jar with the cloth and secure it with a rubber band, then place it in a warm spot, ideally between 75°F and 85°F. The fermentation typically takes seven to fourteen days, depending on the temperature and your desired level of tartness. After seven days, you can begin tasting the kombucha daily using a clean straw to check its flavor development.

• Clean all brewing equipment thoroughly with hot water and mild unscented soap to prevent contamination.
• Brew four to six tea bags in four cups of hot water, then dissolve one cup of sugar.
• Cool the sweetened tea to below 90°F before adding the SCOBY and starter tea.
• Add one to two cups of unflavored starter tea to lower initial pH.
• Ferment for seven to fourteen days at 75°F to 85°F, tasting regularly.

Second fermentation: flavor and fizz

After the first fermentation, your raw kombucha is ready for its second stage, often called F2. This is where you add flavors and create carbonation. Once your kombucha has reached your preferred tartness (usually after seven to fourteen days), remove the SCOBY and set aside one to two cups of the finished kombucha to use as starter tea for your next batch. The remaining kombucha is now ready for bottling. For flavoring, you can use fruit, fruit juice, herbs, or spices. For example, in a sixteen-ounce bottle, you might add one-quarter cup of fresh fruit, such as berries from a summer harvest, or two tablespoons of fruit juice.

Bottling and carbonation

Pour the flavored kombucha into airtight bottles, leaving about one to two inches of headspace at the top of each bottle. This headspace is necessary for carbonation to build safely. Swing-top bottles are a popular choice for their ability to hold pressure effectively. Seal the bottles tightly and let them sit at room temperature, ideally around 70°F, for one to five days. During this time, residual yeast in the kombucha will consume the sugars from your added flavorings, producing carbon dioxide and creating fizz. You can learn more about preserving fruits for this purpose in our dehydrating food guide. After one day, you can “burp” a bottle by opening it briefly to release excess pressure and check for carbonation. Once the desired fizziness is achieved, transfer the bottles to the refrigerator to slow down fermentation and carbonation, helping prevent over-carbonation. Refrigerated kombucha will keep well for several weeks, often up to one month.

• Separate the SCOBY and reserve one to two cups of starter tea from the first ferment.
• Add one-quarter cup of fresh fruit or two tablespoons of juice per sixteen-ounce bottle for flavor.
• Fill airtight bottles, leaving one to two inches of headspace for carbonation.
• Ferment bottled kombucha at room temperature for one to five days.
• Refrigerate finished kombucha to slow fermentation and hold carbonation for up to one month; cold slows the yeast but does not stop it, so keep an eye on sealed bottles even in the fridge.

Troubleshooting and ongoing SCOBY care

Even experienced brewers encounter issues, but most common problems have straightforward solutions. One of the most concerning issues is mold, which appears as dry, fuzzy, raised spots (usually green, black or blue) sitting proud of the surface within the first few days. Do not confuse it with a new SCOBY: a healthy new pellicle forms as a flat, wet, cream-colored film spreading across the whole surface, and the brown stringy strands hanging beneath it are yeast. Mold is fuzzy and dry and grows in discrete patches; a new pellicle is smooth and wet and covers everything. If you see mold, it is best to discard the entire batch, including the SCOBY, and start fresh with new ingredients and a new SCOBY. This often happens if the starter tea amount was insufficient, leading to a high initial pH, or if the brewing temperature was too low, below 68°F.

Maintaining a healthy SCOBY hotel

To ensure you always have a healthy SCOBY available, consider maintaining a “SCOBY hotel.” This is a jar where you store extra SCOBYs in a solution of finished kombucha — about one cup of kombucha per SCOBY — replenished with a small amount of fresh sweetened tea every few weeks. A well-maintained SCOBY hotel can keep your cultures viable for up to six months, providing a backup in case a batch goes bad. When cleaning your brewing vessel, avoid harsh soaps; a solution of one part distilled white vinegar to four parts water works effectively for sanitization without leaving residues that could harm your SCOBY. Regular cleaning, perhaps every three to four batches, helps prevent the buildup of yeast and bacteria on the jar walls.

• Identify mold as fuzzy, dry, or discolored spots, typically green or black.
• Discard moldy batches and SCOBYs immediately to prevent health risks.
• Maintain a SCOBY hotel with extra SCOBYs and starter tea, refreshed every few weeks.
• Store SCOBYs in a hotel for up to six months as a backup.
• Clean brewing vessels with a one-to-four vinegar-water solution every three to four batches.

Choosing your tea and sugar for optimal flavor

The foundation of great kombucha lies in the quality and type of tea and sugar you use. While black tea, particularly varieties like English Breakfast or Ceylon, is the traditional choice due to its full flavor and high nitrogen content that feeds the SCOBY, other teas can produce distinct results [4]. Green tea, for instance, yields a lighter, grassier kombucha, often with a shorter fermentation time of five to ten days compared to black tea’s seven to fourteen days. Oolong tea offers a middle ground, providing a floral and fruity profile. However, avoid teas with added oils, such as Earl Grey, as these can negatively impact the SCOBY’s health over time. Plain granulated cane sugar is the most common and reliable choice, providing readily available food for the culture.

Alternatives and considerations

Some brewers experiment with alternatives like brown sugar or maple syrup, but these can introduce different mineral profiles and microbial communities that may alter the SCOBY’s behavior and the final flavor [5]. For beginners, sticking to white granulated sugar is recommended for consistent results. A typical ratio is one cup of sugar per gallon of brewed tea to provide adequate fuel for fermentation. Using less sugar can lead to a slower fermentation and a more acidic end product, while too much sugar can overwhelm the SCOBY. Always ensure your tea is free from artificial flavors or sweeteners, as these can inhibit the SCOBY’s activity.

• Use black tea for a full flavor and consistent fermentation, typically 7-14 days.
• Experiment with green tea for a lighter, grassier kombucha, fermenting in 5-10 days.
• Avoid teas with added oils or artificial flavors, as they can harm the SCOBY.
• Stick to one cup of granulated cane sugar per gallon of tea for balanced fermentation.
• Consider organic tea if you want to avoid pesticide residues in the brew.

Essential equipment and sanitation practices

Successful kombucha brewing relies heavily on having the right equipment and maintaining rigorous sanitation. Your primary fermentation vessel should be made of glass, like a one-gallon pickle jar or a two-gallon dispenser, as plastic can leach chemicals and metal can react with the acidic kombucha over time. For covering, a tightly woven cloth, such as a coffee filter or a piece of old T-shirt, secured with a rubber band, allows airflow while keeping out fruit flies and dust. For bottling the second ferment, use swing-top glass bottles or bottles rated for carbonated beverages; ordinary jars and repurposed screw-top bottles are not built for pressure and can shatter. No bottle is a substitute for managing the ferment — even a pressure-rated bottle will fail if the second ferment runs long or warm, so burp daily and move everything to the refrigerator as soon as the fizz is right.

Cleaning protocols for safety

Sanitation prevents mold and unwanted bacterial growth. Before each brew, all equipment that comes into contact with the kombucha (including the brewing vessel, stirring spoons, and bottling funnel) must be thoroughly cleaned. Avoid using antibacterial soaps, which can leave residues that harm your SCOBY. Instead, wash with hot water and a mild, unscented dish soap, then rinse thoroughly. For an extra layer of protection, especially if you’ve had issues with mold, you can sanitize your glass vessels by filling them with a solution of one part distilled white vinegar to four parts water and letting it sit for thirty minutes before rinsing. This is similar to the care taken when preparing equipment for fermenting and pickling vegetables, where cleanliness directly impacts safety and flavor. Always ensure your hands are clean when handling the SCOBY, as skin oils and bacteria can introduce contaminants.

• Use glass vessels, such as one-gallon jars, for primary fermentation to avoid chemical leaching.
• Securely cover your fermenting vessel with a breathable cloth to deter pests.
• Opt for swing-top glass bottles for second fermentation to safely contain carbonation.
• Clean all equipment with hot water and mild, unscented soap, avoiding antibacterial residues.
• Sanitize vessels with a one-to-four vinegar-water solution for thirty minutes before rinsing.

Creative flavor variations and additions

The second fermentation is where you can truly personalize your kombucha, infusing it with a wide array of flavors. Fresh fruits are a popular choice, offering natural sugars for carbonation and good flavor. For a sixteen-ounce bottle, one-quarter cup of mashed berries, sliced peaches, or diced apples can provide ample flavor and fizz. In regions like California’s Central Valley, where stone fruits are abundant in summer, using local produce can yield exceptional results. Juices are another simple option; two tablespoons of organic fruit juice, such as grape, cherry, or pineapple, per bottle works well. Herbs like ginger, mint, or lavender can add a sophisticated touch, often requiring just a few thin slices of ginger or a sprig of mint per bottle.

Combining flavors and spices

Don’t be afraid to combine ingredients for complex flavor profiles. A popular combination is ginger and lemon, using one teaspoon of grated ginger and one tablespoon of lemon juice per sixteen-ounce bottle. Spices such as cinnamon sticks, cloves, or star anise can also be incorporated, though in smaller quantities (such as a half-inch cinnamon stick or two whole cloves per bottle) to avoid overpowering the kombucha flavor. For a sweeter, more dessert-like kombucha, you might consider adding a small amount of maple syrup, perhaps one teaspoon per bottle. Remember to always use clean, fresh ingredients to avoid introducing unwanted bacteria. Keeping a log of ingredient combinations helps replicate successful batches.

• Add one-quarter cup of mashed berries or sliced fruit per sixteen-ounce bottle for flavor.
• Use two tablespoons of organic fruit juice per bottle for a simpler flavoring method.
• Infuse with herbs like ginger, mint, or lavender, using small amounts such as one sprig of mint.
• Combine flavors, such as one teaspoon grated ginger and one tablespoon lemon juice per bottle.
• Experiment with spices like a half-inch cinnamon stick or two whole cloves for complex notes.

Health considerations and safe brewing practices

While kombucha is widely enjoyed for its tangy taste, two things belong at the front of any home-brewing guide. First, kombucha contains alcohol: fermentation produces ethanol alongside the acids, and a home brew regularly finishes above the 0.5 percent by volume that separates a soft drink from an alcoholic one, with a long or warm second ferment pushing it higher still. It is not a non-alcoholic drink, and it is not appropriate for children, for anyone pregnant or breastfeeding, or for anyone avoiding alcohol. Second, a home brew is an uncontrolled live culture with no batch testing behind it, so public health guidance is that people who are immunocompromised, pregnant, or living with liver or kidney disease should avoid home-brewed kombucha altogether. The acidic environment of kombucha, with a pH typically between 2.5 and 3.5, naturally inhibits the growth of most harmful bacteria [1]. However, improper sanitation or insufficient starter tea can lead to contamination. Mold is the most common visual indicator of a spoiled batch, appearing as fuzzy, dry patches, often green, black, or white, usually within the first three days of fermentation. If mold is present, the entire batch, including the SCOBY, must be discarded to prevent potential health risks.

Avoiding contamination and maintaining quality

Always ensure your brewing environment is clean and free from pests, especially fruit flies, which are attracted to the sweet tea and can introduce unwanted microorganisms. Using a tightly woven cloth cover, secured with a rubber band, is essential to keep them out while allowing the necessary airflow. Another safety concern is over-carbonation during the second fermentation, which can lead to bursting bottles. To prevent this, leave one to two inches of headspace in each bottle and “burp” them daily by briefly opening the cap to release excess pressure, especially if fermenting for more than three days at room temperature. Refrigerating your finished kombucha after it reaches desired carbonation will slow down fermentation significantly, making it safe to store for up to one month. Adhering to these practices keeps home brewing safe and productive.

• Maintain a pH between 2.5 and 3.5 to inhibit harmful bacterial growth [1].
• Discard any batch showing fuzzy, discolored mold, typically appearing within three days.
• Use a tightly woven cloth cover to prevent fruit flies and other pests from contaminating the brew.
• Leave one to two inches of headspace in bottles during second fermentation to prevent bursting.
• “Burp” bottles daily during F2, especially if fermenting for more than three days, to release pressure.

Comparing kombucha tea bases

Optimal pH: Finished kombucha typically lands between pH 2.5 and 3.5, acidic enough to inhibit the growth of unwanted microorganisms.

Sugar Conversion: The SCOBY consumes most of the sugar over the ferment, but how much is left varies widely between batches and cannot be measured at home.

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Frequently asked questions

How much sugar is left in finished kombucha?

Most of the initial sugar is consumed over a seven to fourteen day ferment, and a more tart batch has less left in it than a sweet one. How much remains varies widely between batches, and there is no reliable way to measure residual sugar in a home brew without lab testing — so do not treat your kombucha as a low-sugar drink on the strength of a general figure.

Can I use honey instead of sugar?

While honey can be used, it contains different microbial profiles that can alter the SCOBY’s balance and may lead to a different fermentation outcome. It’s generally recommended to stick to granulated sugar for consistent results with traditional SCOBYs, though specific honey-based cultures exist [5].

What if my SCOBY sinks?

It is common for a new SCOBY to sink to the bottom of the brewing vessel. This is normal and does not indicate a problem; a new SCOBY layer will typically form on the surface within three to five days as fermentation progresses.

How do I know if my kombucha is ready?

Your kombucha is ready when it reaches your preferred balance of sweetness and tartness, usually between seven and fourteen days. A pH strip reading between 2.5 and 3.5 is a good indicator of readiness for bottling, and you can taste it daily after day seven.

Can I use decaffeinated tea?

Using decaffeinated tea is possible, but the caffeine content in regular tea provides a nitrogen source that supports faster fermentation. Without it, fermentation might be slower, potentially extending the first ferment by several days.

How long can I store starter tea?

Starter tea keeps best at room temperature in a SCOBY hotel, topped up with fresh sweet tea every few weeks. Refrigeration slows the culture and weakens it over time, so use refrigerated starter within a few weeks and expect a sluggish first ferment from it. It’s best to use at least one cup of this acidic liquid per gallon of new sweet tea to ensure proper pH and a strong start for your next batch.

References

1. Kombucha Tea Fermentation: A Review (2020). Kombucha Tea Fermentation: A Review.
2. home-brewing, n. (2026). home-brewing, n..
3. A Review of Coffee Kombucha Brewing and Health Effects as a Fermented Beverage (2025). A Review of Coffee Kombucha Brewing and Health Effects as a Fermented Beverage.
4. Processing Condition Effects on Sensory Profiles of Kombucha through Sensory Descriptive Analysis (2022). Processing Condition Effects on Sensory Profiles of Kombucha through Sensory Descriptive Analysis.
5. “Brewing Biopotency”: HRAMS and FTIR deconvolution of Butea monosperma-derived Kombucha (2026). “Brewing Biopotency”: HRAMS and FTIR deconvolution of Butea monosperma-derived Kombucha.