Why My Kombucha Smell Like Sulfur (or Rotten Eggs)

My Kombucha Batch Smells Like Rotten Eggs – Is This the End?

No. It is not uncommon for kombucha batches to sometimes start giving off a sulfurous smell, similar to rotten eggs. It is normal in that brewers do encounter it from time to time, and it does not mean that the whole thing is toxic and needs to be chucked.

It might indicate a problem with the kombucha SCOBY culture you are brewing with, in which case you will probably need a new culture, but this is not always the case.

What Causes a Sulfurous Smelling Kombucha

A sulfurous smelling brew can be caused by a couple of things. Sometimes certain foreign (or wild) airborne yeasts can integrate themselves and become part of the SCOBY culture.

This is actually desirable, and some brewers recommend that one leaves the sweet tea batch open to the air for a few hours once cooled, to allow airborne yeasts a chance to incorporate themselves. This is because having a culture which contains microbial diversity in the form of a good amount of different yeasts and bacteria, makes for a strong culture.

Yeast Bi-product

However there are some species of these yeasts which can produce sulfur as a bi-product. The sulfur is not poisonous, and is not dangerous to drink.

However, as sulfur can smell very similar to rotten eggs, you might not be able to drink it! Even if you have been tweaking your ferments to get some really unusual tasting finished kombucha, I am sure sulfur was not a flavor you were aiming for.

What To Do

Unfortunately once a species of yeast has incorporated itself into the colony, one cannot selectively remove it. If you think that the yeasts are over active, then you can take measures to subdue them and encourage the bacteria.

This however does not guarantee that your brew will return to normal. If it does there is also always the possibility that if the yeasts become stronger again, then the sulfurous smell will reoccur.

If your sulfurous smelling brew is caused by yeast species within the colony producing sulfur, then the best option is to just dump the lot. If you have any stored SCOBYs, you will then have to decide whether you want to try a new batch with one of them, or just get hold of a new SCOBY completely.

However, before such drastic action is required, there are two other factors that might be causing a sulfurous odor within your brew of kombucha, and which you can remedy.

Water Source

Another possible cause of a sulfur smell can be the presence of hydrogen sulfide in the water that you are using to brew with. If this is the cause of your sulfurous smelling kombucha, it will be quite easy to spot, as the water itself will smell faintly of sulfur. Besides being easy to pinpoint, this is also that complicated to remedy.

What To Do

To avoid this source of hydrogen sulfide which is causing the unpleasant smell in your brew, you can either change to a different kind of water, such store bought purified water, or purify your own water yourself. This is not as complicated as one might think, as different water filters are widely available.

For more info on the best water to use for kombucha brewing, have at a look at What is the Best Water For Kombucha, and for guidelines on filters and ways to purify tap water check out How to Brew Kombucha from Tap Water.

Nitrogen in Tea Leaves

The last factor which could be causing a sulfurous smell in your brewing kombucha is a high amount of nitrogen present in the tea which you are using. This is not necessarily a bad thing, and is merely a factor which can vary between brands and batches.

What to Do

You can try different brands of tea, and see if the ‘sulfery’ smell disappears. However you might find that a different box of the same brand will do the same.

How To Troubleshoot Your Sulfur Issue

If the water which you are using for your kombucha brewing is the source of the sulfur, you will easily be able to tell, as the water will smell of it. Check this first. If it is the water source, change or purify it.

• Smell you water. If the sulfur is not coming from the water, then it is either a high amount of nitrogen present in the tea you are using, or you have yeasts in your SCOBY culture which are producing sulfur.
• Try a different tea. Experimenting with different tea will allow you to gauge whether it is high levels of nitrogen within the tea you are using, or if it is in fact a sulfur producing species of yeast within the SCOBY culture that is causing problems.
• If it’s in the SCOBY. If changing tea does not help at all, then the problem is most probably within the SCOBY. It is then probably best to chuck out your brewing SCOBY, and start over with a fresh culture. If you have any in storage, then you can decide whether you want to try one these – however depending on what point in time the yeast species became part of the culture, there is a possibility that they will have the same problem. Therefore, if you are anxious to get your ready-to-drink kombucha (that doesn’t smell like rotten eggs), and do not want to risk chancing another sulfurous batch, then you might want to purchase a brand new culture. Of course, if you can beg one from a friend, even better!

Can I Drink The Sulfurous Kombucha?

Kombucha which smells like sulfur or rotten eggs, is not unsafe to drink. It might however be difficult to! Sometimes what can happen is that the odor lessens or totally disappears if the kombucha tea is left to stand for some time.

You can try doing a second ferment, and see if it dissipates out. For the low down on second ferments, check out How To Make Second Ferment Kombucha (And Why You Absolutely Should)