Q&A: Why does my kombucha smell like sulfur and/or rotten eggs? Is it safe to drink?

Q: Why does my kombucha smell like sulfur and/or rotten eggs? Is it safe to drink?

A: A rotten egg smell comes from sulfur. The presence of sulfur may be:

• A product of nitrogen from the tea
• From the water source
• Another thread to read on kombucha and sulfur can be found here

Because kombucha and beer are both products of fermentation, the reasons for sulfur/rotten egg smells in beer may be the same for kombucha:

• According to beer brewing sites, sulfur smells in beer may be due to byproducts of certain yeasts, yeast autolysis (yeast cannibalism), or bacterial infection
• The sulfur smell goes away in beer over time according to this thread and FAQ 5.43.

Is the kombucha safe to drink?
According to the threads here and here, it appears that the kombucha is still safe to drink even if it smells like sulfur/rotten eggs. However, if you don't feel good after you drink it, stop!

What can you do?

• If you think the sulfur smells are due to your water source, consider using a water filter or upgrading your current water filter.
• Let your kombucha age for longer periods of time before you drink it to see if the sulfur smells decrease over time.
• If you think the sulfur smells are due to certain yeasts in your kombucha, try favoring the bacteria in your brew.
• Try cleaning all of your equipment and make sure you practice proper sanitation techniques.
• Try starting over with a new SCOBY.

If you have had any experiences with your kombucha smelling like sulfur and/or rotten eggs, have any other suggested solutions, or have any success stories, feel free to share!

Kombucha SCOBY Exchange on Facebook

There are many ways to obtain kombucha cultures, which I describe here.

I would like to present the Kombucha SCOBY Exchange on Facebook, which is sort of a Facebook version of the Worldwide Kombucha Exchange.

I previously suggested that individuals who were looking for SCOBYs or who had extra SCOBYs to share to write a post on Kombucha Fuel's Facebook wall. However, over time, I found that this was not very effective as the requests and offers got pushed down as people wrote new posts on the wall. I have thus created the "Kombucha SCOBY Exchange" as a note on Kombucha Fuel on Facebook. This way, all of the SCOBY requests and offers are together, making it easier for those who are looking for kombucha cultures to connect with individuals in their area who have extra SCOBYs available.

I hope that this will become a helpful resource, and if anyone has any comments, questions, or suggestions, I welcome them.

Below is a copy of the Kombucha SCOBY Exchange note that I have put on Facebook:


Welcome to the Kombucha SCOBY Exchange!

Looking for a kombucha mushroom?
If you are looking for a kombucha mother, write a comment saying that you are looking for a SCOBY and list your location with as much information as you feel comfortable. If someone with extra SCOBYs in your area sees the request, hopefully they will contact you so you can schedule a pick-up!

Have extra kombucha mushrooms to share?
If you have extra kombucha mothers that you would like to share, likewise leave a comment and list your location with as much information as you feel comfortable. This way if someone is looking for a kombucha mushroom in your area, they can contact you! Also, please don't be shy if someone is already offering kombucha mothers in your area. It can be helpful to have multiple people offering SCOBYs in the same area!

Tips:
-You can delete any of your own comment(s) at any time if your situation or location changes.
-If you find someone to connect with, consider contacting them directly. This will help to keep the Kombucha SCOBY Exchange more clutter free and easier to navigate.

Thank you for participating in the Kombucha SCOBY Exchange, and I hope you find this exchange useful!

Happy Brewing,
Annabelle

Kombucha Skillshare and Kombucha Fuel at the UHL Market Stand (Updated July 13, 2010)

*Update: My Kombucha Skillshare is scheduled for 10:45 am this Saturday. Hope to see you there!*
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Join Kombucha Fuel at the UHL Market Stand at the Union Square Farmers Market on July 17th!

What: Kombucha Skillshare (20-25 minutes) and Kombucha Fuel at the UHL Market Stand

When: Saturday, July 17th. Kombucha Fuel at the market stand from 9 am - 1 pm. Kombucha Skillshare at 10:45 am (20-25 minute demo).

Where: UHL Market Stand at the Union Square Farmers Market (1 Union Square, Somerville, MA, 02143)

Description:I will be at the UHL Market Stand from 9 am - 1 pm, to talk to visitors and answer questions about brewing, bottling, and anything kombucha! At 10:45 am, I will lead a Kombucha Skillshare, covering the basics of brewing and bottling the fermented tea kombucha in a 20-25 minute demo.

SCOBYs will be available for those interested in beginning to brew on their own from 9 am - 1 pm. For individuals interested in taking a SCOBY home, bringing a small, clean glass jar would help to facilitate distribution. In spirit of the swap table at the UHL Market Stand, bringing something to swap for the SCOBY would be fun, although it's not required. :)

This demo will be in conjunction with the UHL Market Stand of the Urban Homesteaders' League. They are an awesome group! Read about the Urban Homesteaders' League and check out their blog.

There will also be three other urban homesteading skillshares at the UHL Market Stand on July 17th, see the schedule here.

Bottling and Headroom (Updated July 12, 2010)

***For the update please scroll down to the bottom of this post***

After several readers inquired about leaving headroom when bottling, I felt obligated to experiment.

I had always learned to fill the kombucha all the way to the top when bottling for a secondary fermentation. This stops the activity of the bacteria because of the exclusion of oxygen, while the yeast can continue to ferment the sugars to create CO2 and an effervescent drink, because yeasts can function with or without oxygen (1).

After being prompted to do some experimenting on my own, I left around an inch of headroom in several kombucha bottles for a secondary fermentation. I left the bottles out for a few days, and then I refrigerated them. I didn't open the bottles right away because I already had some kombucha bottles open, but I pulled one out from the refrigerator a week or so later and found that the kombucha bottled with around an inch of headroom was more fizzy than a good number of my previous batches!

Bottling with Headroom
Photo courtesy of Haven Sarah Ripley Daniels

Although Happy Herbalist mentions to fill the kombucha to the top of the bottles in their Brewing Guide (look under "Bottling"), on their Bottling Tips page there is a section "Choosing to leave an airspace." According to their Bottling Tips page, if you leave oxygen and airspace in the bottle and if the temperatures are between 70-85 degrees F, the bacteria will continue to remain active and the kombucha will continue to sour, which makes sense because the bacteria require oxygen.

Meanwhile, the yeasts can function with or without oxygen. However, according to Happy Herbalist, yeasts only form carbon dioxide and fizz when oxygen is present (2). "Carbon dioxide suffocates/diminishes the bacteria, but produce[s] the fizz and sparkling brew. Without oxygen the yeast produce more alcohol...The yeast may be active in temperatures as low as 40F (5C) with or without oxygen" (2). In other words, if you leave headspace when bottling, the yeasts can create more carbon dioxide and fizz because of the oxygen present in the airspace. But if there is no airspace, the ability of the yeasts to produce an effervescent drink is limited because of the limited availability of oxygen.

Unfortunately, I was perfectly happy with this explanation until I returned to this formula from my previous post, Kombucha + Fizz, and could not find oxygen needed in the equation for the yeasts to form carbon dioxide:

The yeasts convert sugar to alcohol + carbon dioxide (3, p. 40)

C6H1206 -> 2C2H5OH + 2CO2
sugar -> alcohol + carbon dioxide

Thus, I am somewhat still confused about the exact relationship between the yeasts, oxygen, carbon dioxide, and kombucha fizz. Perhaps the presence of oxygen helps to encourage the yeasts to form more carbon dioxide and fizz, but its presence is not necessary?

Something to note is that kombucha that is bottled all the way to the top will taste different than kombucha that is bottled with airspace, such as in the amount of fizz produced and in others ways as well, such as the acidity of the drink.

I have not found much information on the recomended amount of airspace if you decide to bottle kombucha this way. However, beer brewers tend to leave 1-2 inches of headspace in their bottles according to this thread. Again, experimentation is key, and do whatever you prefer according to personal preference and taste!

As always, I am continuing to learn more about kombucha day by day, and I hope to share that information. If you have any more information or tips on the bottling process and kombucha fizz, please send the information my way or leave a comment!

All my posts related to bottling can be found here.

References
1. http://www.happyherbalist.com/brewing_kombucha.htm
2. http://www.happyherbalist.com/bottlingtips.aspx
3. Frank, Gunther W. Kombucha - Healthy beverage and natural remedy from the Far East. 4th ed. Austria: Wilhelm Ennsthaler, 1994.

***Update July 12, 2010***

I was able to get to talk to a brewer who brews beer and kombucha. Here is what I learned:

• Confirmation that headroom helps prevent the bottle from exploding from the buildup of carbon dioxide.
• You can still increase the fizz in your brew whether or not you leave headroom in your bottle.
• You won't lose fizz by leaving headspace in the bottle.
• You lose more fizz the more you transfer the kombucha from container to container. You can actually decarbonate your brew by transferring your kombucha from container to container.

In this article from Happy Herbalist, it states that aerobic and anaerobic yeasts in kombucha help to produce carbonation, and that the production of more carbonation than alcohol by both types of yeast is favored when oxygen is present, which is in line with the other Happy Herbalist information (that I am conflicted about) that I provided above.

Part of the reason why there doesn't seem to be a clear answer to the question about whether it is better or not to leave headroom to create more fizz, is because kombucha ferments and SCOBYs contain different strains of bacteria and yeasts and in different proportions. Wild and airborne bacteria and yeasts, which differ according to the location and environment, add even more variation to the mix. Here is one Analysis of a Kombucha Ferment by Happy Herbalist as an example for what may be in your brew.

I personally prefer to bottle with headroom at the moment. But it is up to you, and based on your experiences, to decide whether or not you want to leave headroom in your bottles. I recommend experimenting with both. If anyone wants to share their experiences with bottling, please do so!