What To Do If My Kombucha Tastes Sour
My SCOBY Tastes Very Sour – Why?
Kombucha tea can taste anywhere between quite sweet and very sour or tart. The longer you leave your brew to continue its fermentation process, the more sour and tart it will get, until the taste is almost like vinegar! A very sour taste is not necessarily an indication of anything wrong with your SCOBY or brew.
If you have left the fermentation to continue for longer than usual, then it is quite natural for the taste to be on the sour side. Brewing times vary according to the temperature which the ferment is in, and the age and condition of your SCOBY culture.
One of the best ways to gauge how far your kombucha tea is along its fermentation process is to taste it with a straw. If it is very sweet, then it can be left longer, if it is starting to take on a bit of a tang, and you are happy with the taste, then you can stop the fermentation. For detailed guidelines on how long to ferment your kombucha, read How To Estimate The Perfect Kombucha Brew Time.
The longer you leave your kombucha, the stronger the acidic sour taste will become, and the more potent it will be as well. However, if you like it less tart and acidic, there is no harm in stopping things at the taste that you prefer. Considering that you are busy making good amounts of kombucha tea on a regular basis, strong or not, you will be reaping the health benefits. Rather have your tea at a taste which you enjoy, and drink more of it, than sip down small glasses that make you grimace!
When Things Turn Sour Fast
While kombucha tea naturally gets sourer and sourer the longer it is left to ferment, sometimes it can prematurely sour. This does not mean that it has gone off, and is not safe to drink. However it is an indication that there is a problem with the SCOBY culture. Fermentations which go sour abnormally quickly, and become overly tart before you know it, are an indication that the SCOBY has gone out of balance.
The SCOBY Balance Explained
Kombucha SCOBY cultures are made up of bacteria and yeasts who work together to ferment the sweat tea base which the SCOBY is placed in. They live happily together in their cellulose home, and support each other. However, what can happen is that one proliferates and dominates the culture to the detriment of the other and the kombucha brew. This is caused by conditions in which the culture is living, such as temperature, tea strength etc.
The usual pattern is that upon purchasing, receiving or the bringing out of storage of a new SCOBY, the culture has more bacteria activity, and the yeasts are in a subdued state. This leads to slow fermentations with little carbonation.
Then after one has been brewing for awhile, the yeasts start to become more active and multiply, which negatively affects the bacteria. This can be exacerbated by warm temperatures. Over activity of the yeasts is the more common of the two imbalances, especially after successive brews have taken place.
If you are experiencing overly fast fermentations and premature souring, the most likely the cause is that you have an over enthusiastic yeast population who are smothering their bacteria comrades.
Keeping The SCOBY Balance Makes For Hassle Free Brewing
Continuous successful kombucha brewing and SCOBY care relies largely on tweaking things to keep the SCOBY culture’s yeasts and bacteria populations in balance. Having an understanding of what stimulates which sector of the SCOBY microbes will make ongoing hassle-free kombucha making much more simple and effortless.
While SCOBYs are tough cultures, being able to pick up what is going on with them, and knowing which quick measures to take to rectify any imbalances will help you to make every brew taste exactly the way you want it to, and ensure that you always have a supply of fresh kombucha tea to consume.
Reducing the Yeast Ratio
If you have verified that your ferments are happening way too quickly, and are getting sour super fast, then you’ve got to subdue those yeasts a little. If you are brewing in a warm climate or season, then this is quite normal. The yeasts thrive in warm temperatures, while the bacteria prefer a cooler environment.
1. Control Temperature
Kombucha can be successfully brewed in temperatures between 95o Fahrenheit (35o Celsius) and 49o Fahrenheit (18o Celsius). Below 49o Fahrenheit (18o Celsius) and the culture will start to go to sleep, yeasts first. Above 95o Fahrenheit (35o Celsius) and the bacteria will start to die off rapidly. The closer one gets to the uppermost band, the more prolific the yeasts will become, and the more strain the bacteria will take. Keeping one’s brew at a temperature within the bottom range will discourage the yeasts, encourage the bacteria, and create a situation where the yeasts are back to supporting the bacteria and their processes, rather than rampaging through your fermentation.
If you are experiencing high temperatures where you live, try to find the coolest place in your house. However, if the coolest place is also dark, it might not be ideal, as absence of light can put the SCOBY culture ‘to sleep’, which will result in slow, half measure fermentations, also not what you want!
2. Take Starter Liquid from the Top Area
If you are using starter from your previous kombucha batch, or from your SCOBY Hotel, then try to ensure that you are taking liquid from the top of the container in which it is stored. Liquid from the bottom will contain a higher amount of free floating yeasts. If you can see brown coloured silt or strands, either floating, deposited on the bottom of the brewing vessel, or hanging off of the SCOBY itself, these are some of the yeasts.
3. Wash the SCOBY
Another strategy to reduce the yeasts is to wash the SCOBY in a diluted solution of spirit vinegar. The acidic ph of the vinegar is not harmful to the SCOBY culture, as the culture does best in acidic ph tea solutions, and turns the sweet tea base more and more acidic the longer fermentation continues. However, some brewers advise against washing the SCOBY, as it is possible to wash off too many of the yeasts.
What results you get will depend on the severity of the yeast imbalance present and the thoroughness of the wash you give it. If you want to get rid of the strands of yeast suspended from the bottom of your SCOBY, you can also pull off, or trim off the top layers. For detailed guidelines on how to do this take a look at these articles How To Cut A SCOBY In Half, How To Remove the Baby SCOBY From The Mother and How To Divide A SCOBY (Remove Baby from Mother).
4. Add Glucose & Reducing Tea Strength
A good method to implement when wanting to get the yeasts under control and encourage the bacteria population is to replace a portion of the sugar you are using with glucose. At the same time, reduce the strength of the tea as well. Either let the bags or leaves steep two thirds of the time, or reduce the quantity which you are using by approximately one third. Good glucose sources are karo and corn syrup, corn syrup being the better of the two.
Be sure to use these two strategies in conjunction with each other, as each have an effect on the time at which the yeasts transition from respiration mode into fermentation and how much food is made available to the bacteria. In fermentation mode, the yeasts are supporting the bacteria, and providing them with fuel to work and reproduce quickly. These two tricks often only work effectively if used together, as one compliments the other.
Its’ All About Balance
Its’ all about balance, and by that I mean SCOBY balance! Most brewing problems are directly related to the balance between the yeasts and the bacteria within the SCOBY culture, and the best way to ensure that you are always coming out with optimum brews after fermentation is to keep tabs as best you can on the relationship between the bacteria and yeast populations.
This is not so tricky once you know the sign:
Lots of yeasts = lots of carbonation and very fast ferments, accompanied by a yeasty scented kombucha.
Lots of bacteria = very slow fermentation and low levels of carbonation.
If you live in a warm area it is likely that the yeasts are on the rise (read ourHow to Brew Kombucha in Warm Weather SCOBY Care article) If you live in a cold climate, then they will most probably not be thriving as prolifically, and it might be the bacteria which have the upper hand.
Newly obtained SCOBYs could quite possibly have sleepy yeast populations which you can stimulate a bit. Mature SCOBYs which have gone through quite a few brew cycles might very well be at a point where the yeasts are slightly out of hand, and it is time to curb them, and give the bacteria a chance to come back into balance.
If you want to read more about the bacteria to yeast balance within the SCOBY, check out these two posts dealing with the opposite extreme of carbonation problems What to Do If There is No Carbonation (Fizz) in My Kombucha and What to Do If There is Too Much Fizz in My Kombucha.