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kombucha: the second fermentation is necessary

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· 4 years ago

Obviously you already know the countless benefits that can be obtained from driking kombucha regularly, but perhaps you don't know that the second fermentation kombucha has even healthier nutrients. The yeasts and bacteria that make up the SCOBY (Symbiotic Colony Of Bacteria and Yeast) are still present in Kombucha tea even after you have removed the scoby itself and filtered the ready drink. In fact, most of the colony is true that it remains in the SCOBY (the "mother" you used to start the fermentation of the tea and the "baby" that produced it) but there are millions of other yeasts and bacteria floating in the liquid tea. That's why very often you can find a small, unexpected SCOBY in a bottle of unpasteurized kombucha, since the yeasts and bacteria contained in the bottle have reunited again forming the same colony.

During primary fermentation, SCOBY yeasts use the nutrients from the sweetened tea blend to grow and multiply. During this process, they produce by-products like ethanol. The bacteria take ethanol and use it to feed on it, breaking it down into organic acids. The longer you allow bacteria to work, the more these organic acids will be produced by transforming your kombucha from sweet to sour.

Obviously the result will be the formation of several important acids that have many health benefits:

Gluconic acid helps fight yeast infections like candidiasis.
Lactic acid helps regulate digestion.
Malic acid is a natural detoxifier.

However the main acid produced is acetic acid , which is another name for vinegar. The longer the bacteria work, the more kombucha tea becomes acidic and acetic, especially during primary fermentation. An advantage therefore of secondary fermentation is that it slows down the production of acetic acid, which means that the nutritional value of kombucha will continue to increase without it becoming too quickly acidic.
With longer fermentation periods, antimicrobial compounds also build up, making second fermentation kombucha a more effective antioxidant. At the same time, sugar will continue to decline, making kombucha a healthier drink, especially for people who are concerned about their diabetes.

More carbonation (production of bubbles)

Yeasts also produce carbon dioxide, giving the fresh kombucha tea a light sparkling note. But since this first production is done in an aerobic environment, much of the CO2 escapes. It is important, in fact, to cover the fermentation container with a piece of thinly woven cloth to protect the SCOBY from molds and contaminants that circulate in the air and allow enough oxygen to enter so that the SCOBY yeasts can breathe while "eating" the tea and reproduce. Obviously, the same material allows the carbon dioxide produced by the yeast to escape at the same time, therefore air enters your sheet and carbon dioxide escapes.
During the second fermentation, when the SCOBY has now been removed and the fermentation container (this time usually a bottle) is well sealed, yeasts and bacteria go to the anaerobic phase, which does not require oxygen (the little left over is immediately consumed). At this stage all carbon dioxide remains "captured" in the kombucha - at least as long as the container remains sealed! That's why you have to make sure you have good robust bottles with a firm closure when you make the second fermentation.

More quantities of alcohol

Freshly prepared kombucha has very little alcohol. Bacteria convert most of the ethanol produced by the yeast into organic acids, so Kombucha tea is generally safe to drink for anyone, even children. We will find an average of 0.5% ABV (alcohol by volume or alcoholic strength if expressed by the "% vol" symbol; the expression has replaced the one commonly used in alcohol content).

A kombucha after the first fermentation will be even less alcoholic than the beer called "lite". However, as kombucha continues to ferment even after being bottled, the longer it is in the bottle the more alcohol will tend to accumulate - although it will rarely exceed 2-3% ABV - and for this, the Food and Drug Administration in the States passed a law in 2010 governing the sale and labeling of bottled kombucha. This is another reason, for commercial productions, which put kombucha in bottles that are soon pasteurized; pasteurization in fact killing the yeasts and in fact also interrupts the transformation of sugars into ethanol.

This is one of the reasons why a new mother cannot be obtained from a bottle of pasteurized kombucha, to do this you will need raw kombucha that has its entire share of live yeasts and bacteria.

When you make the second fermentation of kombucha in well corked bottles, as we said, keeping them at room temperature for a few days, you will increase the alcohol content by a little. However, if you add more "yeast food" with which they can continue to work (I speak of other sugar, fresh fruit, dried fruit, etc.) in your bottles, you will end up having a Kombucha tea that could even reach 2- 5% ABV, depending on how many and which ingredients you have added.

NOTE: Kombucha alcohol can be created by adding wine yeast or champagne yeast along with extra sugar and other ingredients, but in general this is not something that is done directly in the bottles and requires some specialized components and equipment.

In the second fermentation you have more possibilities to add flavors

You can use the second fermentation to add flavor to your kombucha, without jeopardizing your SCOBY. In fact, some ingredients, such as raw honey, fresh fruit and whole spices, have the ability to introduce mold and / or other contaminants that would damage the native yeasts and bacteria that populate your SCOBY. During the second fermentation, the SCOBY will have been removed and any possible contaminant on the added ingredients will have difficulty growing in the oxygen-free environment and high acidity like that of a mature kombucha.

NOTE: there is still a risk of contamination during the second fermentation, so make sure to respect the usual conditions of hygiene of the designated places and the containers that will be used.

It is enough to bottle the Kombucha tea, now ripe and separate from the scoby, to make it last long. Second fermentation kombucha can be stored and / or aged for several months. However, it is necessary to use the right types of containers, both for the second fermentation and for the bottling of the kombucha (even if the second fermentation is often done directly in the bottle).

But let's take a look:

Glass jars are popular choices of many lovers who produce their kombucha especially if they also love to make homemade jams and jellies, or some of the many fermented vegetables so rich in probiotics. The jars for this purpose have lids that seal quite tightly, although a certain amount of CO2 will escape from the sides of the screw lid. Plastic lids are much better and more suitable than normal metal lids, due to the acidity of Kombucha tea.
Normal plastic bottles from mineral water or soda work very well for the second fermentation and some people prefer them because it is easy to see how much pressure has accumulated by simply squeezing the sides of the bottle. Make sure they are completely clean before using them and discard them after a few uses because the acid will begin to degrade the plastic. Their use is interesting for the second fermentation as long as it is short term.
The glass bottles that you can get or buy those with the screw cap are ideal for the second fermentation, also because they often contained mineral water. Again make sure they are perfectly clean and dry before using them.
The flip-top bottles with ceramic or plastic caps blocked by a metal lock are probably the best choice for the second fermentation. These Grolsch-style bottles require a small investment (they are not as cheap as recycled plastic water bottles) but if you take care of them, you can use them for years - and they will surely make you look like a professional when you serve kombucha to your friends.
Containers with air intakes allow excess carbon dioxide to escape without releasing too much carbonation into the liquid. You can buy plastic or glass containers for the fermentation of food in any shop specializing in the production of beer and you can also buy the lids with the valve, the airloch or other vent systems. These will be the best choice for long-term fermentation that requires kombucha alcohol production.

Before using any bottle, jar or other container, always make sure that they do not have cracks or chippings and that the cap or lid fits perfectly and is firm.

Learn to plan the second fermentation already when you prepare your Kombucha tea

The reason why you have to think about the second fermentation also during the primary fermentation process is that you have to check the pH and acidity of the kombucha tea so that it gives you the best results when you then use it for the second fermentation. I summarize the reasons:

The flavors that develop during the preparation of the tea will be transferred to the final product. If you have experimented with the use of herbal teas in the preparation of your kombucha, or modified the quantity of sugar or the type of sugar used, keep in mind that you will transfer these flavors to all the bottles of the second fermentation.
The sugar / acid balance must be weighted towards "sweet" rather than "acid". There are two reasons for this. First, if you have a very sour Kombucha tea, it will be difficult to adjust the flavor during the second fermentation, even if you add more sugar. Secondly, those sugars are needed if you want the extra carbonation produced by the action of the yeasts. If there is no sugar to work with, the yeasts will become dormant or die and, of course, you will not get an increase in CO2. Even if you like to drink kombucha tea when it is slightly acidic, you must stop the primary fermentation while the kombucha is still sweet tasting. Check that the pH is around 2.9-3.1. When, with a little experience, you will learn (approaching the day of bottling) to taste your production daily, you will be able to evaluate how the sweet / slightly acidic balancing point should be.
SCOBY needs the right mix of nutrients. Sugar also plays a role in primary fermentation because that's what SCOBY is processing as food. To work more efficiently, SCOBY yeasts need sucrose and glucose (sucrose is a mixture of glucose and fructose). If you are trying to find a way to use other types of sweetener, primary fermentation may take longer, which will change the balance of yeasts, bacteria and nutrients in tea before even starting secondary fermentation. SCOBY also uses caffeine, polyphenols and other nutrients contained in tea leaves. In fact, in the absence of these nutrients, SCOBY will eventually die (literally of starvation). If you are trying different types of herbal teas to evaluate the results, make sure you have a good supply of reserve SCOBY that you will have kept in your Scoby Hotel.

Once you have finished making your sweet and delicious kombucha tea, the small scoby that will have formed together with the mother will both be used to start your next batch of Kombucha tea and you will separate it from the mother as soon as it has grown enough to be autonomous (a little often), usually it will take at least two / three fermentations. Remember to set aside some Kombucha tea to bring new and rich nourishment to your SCOBY hotel, or to use it as a starting culture for your next batch. Now, you can decide how much kombucha you will have to do to have the quantity necessary for the second fermentation.

Ready for bottling?

If you do not want to add other ingredients, you can remove the scoby, filter the drink or not and put it in the bottle, well capped and keep it cool, the flavor will remain substantially the same. When filling a bottle of kombucha without leaving room for oxygen (or at least leaving only a small space at the top of the neck of the bottle) the bacteria will stop working as soon as there is no more oxygen in the liquid. Yeast is able to continue working in this anaerobic environment, but even this will stop working as soon as there is no sugar left to feed on.

Since it's the bacteria that make the acids, your kombucha won't become much more acidic without that extra oxygen. Since you have stopped primary fermentation in the "still sweet" phase, this simple kombucha may be too sweet for you right now. If you want it harsher, all you have to do is fill the bottle less! In other words, leave a few inches of space between the liquid and the stopper in the bottle and the bacteria will use it to continue creating their organic acids. After a few days, you will have the sour taste as you prefer it.

The most recommended bottles to use for Kombucha?

If you want to shop and a very professional product, I highly recommend buying the bottles with the EZ Cap closure for your second fermentation. The reason is that: 1) with these you get a deeper ferment with more foam because the caps seal the bottle completely and particularly well 2) the space between the top and the Kombucha liquid is very small and this allows you to significantly increase the effervescence (much more than if you used a large jar), 3) they are small in size, easy to handle with one hand , which means you will have the joy of drinking your Kombucha as if it were a fizzy drink! You can find them equipped with this cap of different capacities and then choose if only for your personal and daily consumption or for sharing.

Addition of flavors for the second fermentation

Now that the SCOBY has been filtered and secured, you can go wild and get creative! If you are not sure where to start, think of the bottled kombucha that you liked the most and try to replicate its flavor, or you can chase the taste of your favorite ice cream, or your favorite drink, your favorite biscuit, even the old ones Your mom's cookbooks are all sources of inspiration when it comes to developing delicious flavors recipes for kombucha.
Here are some ideas you can try:

fresh grated ginger, blueberry juice, fresh mint leaves
sliced banana, unsweetened coconut sweetened, rum extract
frozen strawberries, canned pineapple in syrup, fresh basil leaves
dark chocolate, frozen cherries, vanilla extract, honey
tangerine juice, peaches in syrup, lemon zest, maple syrup
whole cinnamon stick, whole cloves, apple juice, vanilla extract, brown sugar

When it comes to adding extra ingredients to flavor, however, there are a few things to keep in mind.

Is there enough sugar? Yeast needs sugar to keep working, so we recommend adding something like fruit juice or extra sweetener to give it the nutrients it needs. Some juices have already added sugar, such as cranberry juice. Other juices, such as apple and grapes, are usually sweet enough to be used on their own.

How much should you use it? The amount of added flavorings depends on what you are using to impart that flavor. This will be different depending on whether you are using fresh fruit or dried fruit, whole spices or ground spices, sweetened syrup or unsweetened fruit juice. Here are some guidelines:

For every four liters of kombucha tea, use at least one of the following:

1 or 2 cups of fresh or frozen fruit
1/2 or 1 cup of fruit puree
1/2 or 1 cup of dried fruit
1 or 2 cups of fruit juice
1/2 or 1 cup of additional sweetener
1/2 or 1 cup of fresh herbs or spices
2 or 3 bags of herbal tea
2 or 3 teaspoons of whole dried spices
1 or 3 tablespoons of dried ground spices

A good way to get started is to use smaller quantities to see if you like the result. Some flavors will come very strong, such as mint and ginger, while other ingredients (such as maple syrup) will bring a more subtle flavor.

NOTE: If you use ground spices, it is best to keep them in a small muslin bag to keep them so that they do not cloud the liquid and can be easily removed before the flavor becomes too strong.

How long should I leave the extra ingredients in the container? Again you need to check to see how the flavor develops. If you are using fresh fruit or vegetables (it is possible to prepare excellent vegan kombucha), they may start to become soft after a few days and make your kombucha cloudy, also you will have to be very careful that mold does not also develop, especially in the parts where fruit or vegetables will remain out of the liquid.

Do I then have to remove the ingredients? It depends on you. If you plan on keeping your kombucha for more than a week, it is certainly best to filter all solids before filling the containers or bottles with kombucha. Anything like whole spices and dried fruit that could also cause a choking hazard should still be removed either when you bottle the kombucha or just before drinking it. If you prepared strawberry and kiwi kombucha instead that you are thinking of mixing them with your morning smoothie every day for the next week, you can leave the fruit in the containers and pour everything into the blender.

Planning the needed time

A rule of thumb with refermentation is "one day at room temperature, one week in the cool". Generally it is the minimum time that you will spend making secondary fermentation, which starts at room temperature and continues in a cooler environment. After fermentation at room temperature, remove the added ingredients (or not) and transfer the kombucha to the bottles for storage (unless they are already in the bottle). The second fermentation of kombucha lasts a few days up to a few weeks. Some people like to age their kombucha for a month or more in cool environments such as a cellar.

If these instructions seem a little vague, it is because there are many variables in kombucha production. The temperature in your fermentation room (many of us use the kitchen), the time of year, the size of the container you are using, the strength of the brewed tea and the type of tea you have used, the added ingredients you have chosen and the health of the SCOBY that you used to make tea will all affect how the second fermentation evolves. It is a good idea to have a notebook on hand to write exactly what you do, what you add (and how much), what the temperature is, how long the kombucha is left to ferment and what the results are. Once you have tried a few lots, you will have a better idea of what you can expect from your SCOBY, from your kombucha tea and from putting the ingredients together.

Fermentation in batches compared to fermentation in the bottle

You can make your second fermentation in a large container, or directly in individual bottles. Which method to choose will depend on how you want to flavor your kombucha and how much space you have for storage and refrigeration. Regardless of the size of the container you choose, it is necessary that it is equipped with a lid capable of closing tightly, but that it is easy to open when you want to let out the excess carbonation. If a larger container is used, it is often more convenient to use a container also equipped with a vent valve.

The advantage of using a large container for the second fermentation is that you don't have to worry about taking care of multiple bottles during the fermentation period. If you are using a container equipped with a vent valve, you will not have to pay attention to the pressure that will build up at all. Since the first part of the fermentation is at room temperature, you may even leave the container unattended as you leave for the weekend, and you won't have to worry about going home to witness the explosion of half a dozen bottles on your countertop .

Another advantage of a large container is that it will be easier to add ingredients. Instead of trying to divide a cup of blueberries between several bottles, you can simply rinse the berries and pour them into the container. It will also be easier to filter the ingredients from one container instead of several (keep in mind that whole fruit will absorb the liquid and tend to increase in volume) if you decide to do it.

When adding fruit and spices, the second fermentation takes place directly in the bottles, the need for re-bottling is eliminated, which can make life easier by saving time and cleaning. However, you will need to pay attention to which aromatic ingredients you use, and choose only those that will not cause problems by remaining in the bottle.

Second fermentation at room temperature

Prepare your ingredients:

Cut one or more fresh fruits such as bananas, apples, peaches and watermelons.
Mash the fresh berries to release the maximum flavor.
Do not thaw frozen berries; add them as they are.
Wrap the spices, fresh herbs and ground spices in a muslin bag to make removal easier.
If you use natural hard sugar such as jaggery or panela, turn them previously into a powder so that they easily dissolve in kombucha tea.

Add all your ingredients to the fermentation container (s) and then pour the Kombucha tea over the ingredients. Mix well to dissolve the extra sugar you have added and to mix the flavors. Close the container (s) tightly with their lids.

Place the container (s) in a dark place at room temperature of 25 ° C if possible. Cooler temperatures will make the fermentation longer, on the contrary, warmer will accelerate it and with this also carbonation.

Let the infusion ferment for 1 or 3 days, paying attention to the excess carbonation.

Second fermentation at low temperature

During this phase, the flavors of kombucha have the opportunity to mix and sweeten. A small amount of carbonation will continue as long as there are sugars to be transformed for the yeasts and until the temperature is really too low because in this condition the yeasts "fall asleep". If you put your kombucha in the refrigerator, the action of the yeast will stop almost completely.

The filtered kombucha that made the second fermentation can last several months, provided that the seal on the bottle is tight. If you are thinking of starting a small-scale kombucha production operation, you could have a capper for bottles (like beer) with crown caps. These create a very tight seal that will allow you to keep your kombucha even longer, simply being able to have a fairly cool place out of sunlight.

Some final suggestions

Even if you have kept your kombucha bottles in the refrigerator, especially the first few times and especially if you have left aromatic ingredients inside; in particular the ginger will certainly continue carbonation. When you are about to open a bottle of kombucha, it will be a good idea to do it on the sink holding the bottle firmly in your hands and maybe even wrapped in a tea towel around the top of the bottle, in case you start spraying. Open the cap very slowly to give the stored CO2 the possibility to escape, instead of going out in a large jet that will also carry a large part of the liquid.

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