Brewing Kombucha With Coffee: An Alternative Method

Quick answer

• You can use coffee as a base for kombucha, but it’s not a typical or recommended method.
• Coffee’s acidity and flavor profile differ significantly from tea, which is the standard kombucha base.
• The fermentation process might be unpredictable due to coffee’s unique compounds.
• SCOBYs (Symbiotic Culture Of Bacteria and Yeast) are accustomed to tea’s nutrients and may struggle or produce off-flavors with coffee.
• If you decide to try, start with a small batch and monitor it closely.
• Be prepared for a very different flavor profile compared to traditional kombucha.

While coffee can be used, it’s not the standard for kombucha. If you’re looking to start brewing kombucha, a dedicated kombucha brewing kit is highly recommended for a more predictable and successful first batch.

Who this is for

• Experienced homebrewers looking to experiment with unconventional kombucha bases.
• Adventurous individuals curious about alternative fermentation ingredients.
• Those who enjoy the challenge of pushing the boundaries of common brewing practices.

What to check first

Brewer type and filter type

While this section is usually critical for coffee brewing, for kombucha, it’s less about the brewer and more about the vessel. The “brewer” for kombucha is the fermentation vessel.

• Vessel Type: Ensure you’re using a food-grade glass jar or ceramic crock. Avoid metal or plastic containers, as they can react with the acidic kombucha.
• Filter Type: For kombucha, you typically don’t use a filter in the traditional coffee sense. Instead, you’ll cover the opening of your fermentation vessel with a breathable cloth (like cheesecloth or a clean tea towel) secured with a rubber band. This allows air exchange while keeping out fruit flies and contaminants.

Water quality and temperature

Water quality is important for both coffee and kombucha, but the temperature requirements differ significantly.

• Water Quality: For kombucha, filtered or spring water is best. Tap water can contain chlorine or other chemicals that may harm the SCOBY. If you must use tap water, let it sit out for 24 hours to allow chlorine to dissipate, or use a water filter.
• Water Temperature: For kombucha, you’ll be heating water to dissolve sugar and steep your “base” ingredient. The exact temperature isn’t as critical as it is for coffee extraction, but you’ll want it hot enough to dissolve the sugar fully. After brewing and cooling, the mixture must be brought to room temperature (68-78°F) before adding your SCOBY.

Grind size and coffee freshness

For kombucha, the concept of “grind size” and “coffee freshness” is adapted to how you prepare your coffee base.

• Coffee Preparation: Instead of grinding beans for a specific brew method, you’ll be brewing coffee. The strength and type of brew will impact the final kombucha. A strong, cold brew or a French press might be gentler on the SCOBY than a very hot, high-pressure espresso.
• Coffee Freshness: While fresh coffee is ideal for drinking, for fermentation, the primary concern is avoiding stale or rancid coffee. Stale coffee might introduce off-flavors that are difficult to ferment out.

Coffee-to-water ratio

This is a crucial adjustment when substituting coffee for tea in kombucha brewing.

• Ratio: Traditional kombucha uses about 1/4 cup of sugar per quart of liquid. For coffee, you’ll need to consider how much coffee to use per gallon of water. A typical coffee brew ratio might be around 1:15 to 1:18 (coffee grounds to water by weight). However, for kombucha, you’re not extracting flavor as intensely as for drinking. You might start with a weaker coffee concentration, perhaps closer to a 1:20 or 1:25 ratio, to avoid overwhelming the SCOBY. Experimentation is key here.

Cleanliness/descale status

Sanitation is paramount for successful kombucha brewing, just as it is for coffee makers.

• Cleanliness: Thoroughly clean your fermentation vessel, stirring utensils, and any equipment that will come into contact with the brew. Residue from previous brews or cleaning agents can negatively impact fermentation and introduce unwanted bacteria or mold.
• Descale Status: While coffee makers need descaling to remove mineral buildup, kombucha vessels don’t accumulate minerals in the same way. However, ensuring there’s no lingering residue from cleaning solutions is critical. Rinse thoroughly after washing.

Step-by-step (brew workflow)

1. Prepare Your Coffee Base: Brew a strong batch of coffee using your preferred method (e.g., French press, pour-over, or cold brew). Aim for a concentrated flavor without excessive bitterness. For a 1-gallon batch, you might start with about 8-10 cups of brewed coffee.

• What “good” looks like: A robust coffee aroma and flavor, but not so bitter that it’s unpleasant to taste a small amount.
• Common mistake: Brewing coffee too weak, which might not provide enough initial “food” for the SCOBY, or brewing it too bitter, which can hinder fermentation.
• How to avoid: Taste your brewed coffee. If it’s too mild, brew it stronger next time. If it’s overwhelmingly bitter, consider a different brewing method or using less coffee.

2. Add Sugar: While coffee itself contains some compounds, sugar is essential food for the SCOBY. Add the appropriate amount of sugar (typically 1 cup of granulated sugar per gallon of liquid) to your warm brewed coffee.

• What “good” looks like: The sugar is fully dissolved, and the liquid is clear.
• Common mistake: Not dissolving the sugar completely, leaving gritty sugar at the bottom.
• How to avoid: Stir the mixture thoroughly until all sugar crystals are gone.

3. Dilute with Water: Add filtered or spring water to reach your desired volume (e.g., 1 gallon).

• What “good” looks like: The liquid is well-mixed, and the coffee color is slightly diluted.
• Common mistake: Adding too much water, making the coffee base too weak for fermentation.
• How to avoid: Measure your brewed coffee and water accurately to achieve your target ratio.

4. Cool to Room Temperature: This is a critical step. The coffee-sugar mixture must cool down to between 68-78°F.

• What “good” looks like: The liquid is no longer warm to the touch.
• Common mistake: Adding the SCOBY to hot liquid, which will kill it.
• How to avoid: Use a thermometer to check the temperature, or wait several hours until it feels comfortably room temperature.

5. Add SCOBY and Starter Liquid: Gently place your SCOBY into the cooled coffee-sugar liquid. Add about 1-2 cups of starter liquid (previous batch of kombucha or store-bought unpasteurized kombucha) to help acidify the new brew.

• What “good” looks like: The SCOBY is floating or submerged, and the starter liquid is incorporated.
• Common mistake: Forcing the SCOBY into the liquid or using insufficient starter liquid.
• How to avoid: Handle the SCOBY gently. Ensure you have enough starter liquid to lower the pH.

6. Cover the Vessel: Secure a breathable cloth (like cheesecloth or a clean tea towel) over the opening of the fermentation jar with a rubber band.

• What “good” looks like: The cover is snug and secure, preventing contaminants while allowing airflow.
• Common mistake: Using a lid that seals tightly, suffocating the SCOBY and preventing proper fermentation.
• How to avoid: Ensure the cloth is breathable and the seal is not airtight.

7. Ferment (First Fermentation – F1): Place the jar in a dark, quiet place with a stable room temperature (68-78°F) for 7-21 days.

• What “good” looks like: You’ll start to see small bubbles forming, and a new layer of SCOBY may begin to grow on the surface. The liquid will gradually become less sweet and more tart.
• Common mistake: Moving the jar frequently or exposing it to direct sunlight, which can disrupt fermentation.
• How to avoid: Find a suitable spot and leave it undisturbed.

8. Taste Test: After about 7 days, begin tasting your brew daily using a clean straw or spoon.

• What “good” looks like: The flavor is developing from sweet to tart, with subtle coffee notes. It should be palatable to your taste.
• Common mistake: Waiting too long to taste, resulting in an overly vinegary brew.
• How to avoid: Start tasting early and often to find your preferred balance of sweet and tart.

9. Bottle (Second Fermentation – F2, Optional): Once the kombucha reaches your desired tartness, you can bottle it for carbonation and flavoring.

• What “good” looks like: The kombucha has a pleasant tartness.
• Common mistake: Bottling too early or too late, leading to flat or overly carbonated (explosive) results.
• How to avoid: Ensure the F1 is at your preferred taste before bottling.

10. Add Flavorings (Optional): If bottling, add fruits, herbs, or juices to the bottles before sealing.

• What “good” looks like: The flavorings are added in appropriate amounts.
• Common mistake: Adding too much sugar from fruit, which can lead to excessive carbonation.
• How to avoid: Be mindful of the sugar content in your flavorings.

11. Second Fermentation (F2): Seal the bottles and let them sit at room temperature for 1-5 days to carbonate.

• What “good” looks like: Bubbles form inside the bottle, indicating carbonation.
• Common mistake: Over-carbonating, which can cause bottles to explode.
• How to avoid: “Burp” the bottles daily by briefly opening the cap to release excess pressure.

12. Refrigerate: Once carbonated to your liking, refrigerate the bottles to stop fermentation and chill.

• What “good” looks like: The kombucha is cold and fizzy.
• Common mistake: Forgetting to refrigerate, allowing fermentation to continue and potentially build too much pressure.
• How to avoid: Place bottles in the refrigerator as soon as they reach the desired carbonation level.

Common mistakes (and what happens if you ignore them)

Mistake	What it causes	Fix
Using hot liquid to add SCOBY	Kills the SCOBY, preventing fermentation.	Always cool the brew to room temperature (68-78°F) before adding the SCOBY and starter liquid.
Using tap water with chlorine	Chlorine can harm or kill the beneficial bacteria and yeast in the SCOBY.	Use filtered, spring, or dechlorinated tap water.
Not dissolving sugar completely	Undissolved sugar can lead to uneven fermentation and can be mistaken for mold.	Stir thoroughly until all sugar is dissolved.
Using metallic or reactive containers	Metals can leach into the acidic kombucha, affecting taste and potentially creating unsafe compounds.	Always use food-grade glass or ceramic fermentation vessels.
Sealing the fermentation jar tightly	Prevents necessary airflow and can lead to an anaerobic environment unsuitable for kombucha fermentation.	Use a breathable cloth cover secured with a rubber band.
Using too much coffee	Can result in a brew that is too acidic or bitter, potentially inhibiting SCOBY activity.	Start with a milder coffee concentration and adjust in subsequent batches.
Not using enough starter liquid	Insufficient starter liquid means the brew won’t acidify quickly enough, making it susceptible to mold.	Use at least 1-2 cups of starter liquid per gallon of brew.
Ignoring the brew during fermentation	You miss signs of mold or other issues, or you let it ferment too long, making it too vinegary.	Taste your brew regularly after the first week and visually inspect for mold.
Bottling with too much headspace or too little	Too much headspace can lead to flat kombucha; too little can cause excessive pressure buildup and explosions.	Fill bottles to about 1-2 inches from the top for F2.
Not refrigerating bottled kombucha promptly	Fermentation continues, potentially leading to dangerous over-carbonation and explosions.	Refrigerate bottles as soon as they reach your desired carbonation level.
Using coffee with artificial sweeteners	Artificial sweeteners do not provide food for the SCOBY and can interfere with fermentation.	Stick to natural sugars like granulated cane sugar.
Brewing in a location with fluctuating temps	Temperature swings can stress the SCOBY and lead to inconsistent or stalled fermentation.	Find a stable location with consistent room temperature (68-78°F).

Decision rules (simple if/then)

• If you see fuzzy, colored growth on the surface of your kombucha, then discard the entire batch because it is mold.
• If your kombucha tastes overly vinegary after 7 days, then you have likely fermented it too long for your preference, and you should bottle it sooner next time or use it as starter liquid.
• If your kombucha tastes too sweet after 21 days, then the SCOBY may be weak, the temperature too low, or there’s an imbalance of nutrients, and you should check your SCOBY health and fermentation environment.
• If you are new to kombucha brewing, then start with traditional tea before experimenting with coffee because tea provides a more predictable fermentation environment.
• If you notice a strong, unpleasant smell (like rotten eggs or sewage), then it’s likely a sign of bad bacteria, and you should discard the batch and sanitize everything thoroughly.
• If your SCOBY sinks to the bottom, then don’t worry, as it is normal; it doesn’t affect the fermentation process.
• If you are aiming for a fizzy kombucha, then a second fermentation (F2) in sealed bottles is necessary because this is where carbonation develops.
• If you are using a very dark roast coffee, then expect a bolder, potentially more bitter flavor profile in your kombucha, which may require adjustments in sugar or fermentation time.
• If you want to avoid a strong coffee flavor, then consider using a lighter roast or diluting your coffee base more significantly with water.
• If you are experiencing slow fermentation, then ensure your room temperature is within the ideal range (68-78°F) and that you have enough active starter liquid.
• If your new SCOBY is thin and wispy, then it’s still developing and may need more time to mature and become a robust culture.
• If you are unsure about the safety of your brew, then err on the side of caution and discard it; a healthy kombucha should smell pleasant and slightly acidic.

FAQ

Can I use instant coffee to make kombucha?

While technically possible, it’s generally not recommended. Instant coffee often contains additives and may not provide the complex nutrients that a SCOBY thrives on, potentially leading to a weak or off-tasting brew.

Will my SCOBY die if I use coffee?

It’s possible, especially if the coffee is too acidic, bitter, or if there are other compounds that are toxic to the SCOBY. Always start with a healthy SCOBY and starter liquid, and monitor the brew closely.

What kind of coffee is best for brewing kombucha?

If you decide to experiment, a medium roast, well-brewed coffee without added flavorings or artificial sweeteners is likely your best bet. Avoid very dark, bitter roasts or coffees with oils that might interfere with the SCOBY.

How long should I ferment coffee kombucha?

The fermentation time can vary significantly. It might ferment faster or slower than tea kombucha. Start tasting around day 7 and continue daily until it reaches your desired balance of sweet and tart, which could be anywhere from 7 to 21 days or even longer.

Will coffee kombucha taste like coffee?

Yes, it will likely have a noticeable coffee flavor, but it will also be tart and slightly vinegary, characteristic of kombucha. The intensity of the coffee flavor will depend on how strongly you brewed your coffee base.

Can I get mold when brewing with coffee?

Mold is a risk with any kombucha brew if conditions aren’t right. Factors like insufficient starter liquid, improper temperature, or contamination can lead to mold, regardless of the base ingredient.

Is coffee kombucha safe to drink?

If brewed correctly with proper sanitation and a healthy SCOBY, coffee kombucha can be safe. However, because it’s an unconventional method, it’s crucial to be extra vigilant about signs of spoilage or mold.

What if my coffee kombucha smells bad?

A healthy kombucha should have a pleasant, slightly vinegary, and sometimes fruity aroma. If it smells foul, like rotten eggs, sewage, or strong nail polish remover, it’s a sign of contamination or an unhealthy fermentation, and you should discard it.

What this page does NOT cover (and where to go next)

• Detailed analysis of the specific chemical compounds in coffee that might affect fermentation. (Next: Research the science behind kombucha fermentation and the impact of different organic acids and compounds.)
• Specific brand recommendations for coffee beans or brewing equipment. (Next: Explore guides on choosing coffee beans and brewing methods for optimal flavor extraction in general coffee preparation.)
• Advanced techniques for cultivating and maintaining a robust SCOBY for unconventional bases. (Next: Look for resources on SCOBY health, troubleshooting, and advanced kombucha brewing techniques.)
• Nutritional breakdowns or health claims associated with coffee kombucha. (Next: Consult with a registered dietitian or nutritionist for information on the health aspects of fermented beverages.)
• Recipes for second fermentation (F2) specific to coffee kombucha. (Next: Experiment with complementary flavors like vanilla, chocolate, or spices that pair well with coffee.)