LA SEGUNDA FERMENTACIÓN DE LA KOMBUCHA

The second fermentation of kombucha

If you have come this far it is because you already know that kombucha is a fermented drink. In fact, it is fermented by a colony of yeast and bacteria (SCOBY) that are capable of transforming sugar into organic acids that are responsible for the healthy properties of kombucha. An important detail of this first fermentation is that it is carried out in the presence of oxygen ( aerobic fermentation ). And this is very important because the bacteria present in kombucha need oxygen to ferment. Yeasts… too!, but with nuances. Yeasts can function both with the presence and absence of oxygen. If they have oxygen, they "breathe"; If they do not have to "ferment", and this means that they make alcohol and CO2.

En esta primera etapa lo que queremos es que las levaduras se encarguen de romper las moléculas de sucrosa en glucosa y fructosa (esto lo hacen a partir de segregar una enzima que se llama invertasa), ya que las bacterias no pueden metabolizar la sucrosa, pero sí en cambio la glucosa y la fructosa.

Pues bien, cuando hemos tenido nuestra kombucha fermentando en un depósito tapado con un paño, justamente para que disponga de oxígeno, pero no se pueda contaminar por insectos o polvo, y está en un punto de sabor y acidez que nos gusta, ha llegado el momento de embotellarla. Ahora le podemos añadir zumos de frutas para darle ese sabor que nos gusta. Es muy habitual añadir jengibre, cúrcuma, limón, naranja, fresas, etc. Si ahora queremos transformar esta deliciosa bebida en una bebida burbujeante, lo único que tenemos que hacer es dejarla reposar a temperatura ambiente para que las levaduras hagan su trabajo: CO2. Para que esto ocurra, tenemos que tener azúcar, levaduras viables y temperatura. Con estos tres elementos, es cuestión de días que nuestra bebida recobre vida con esas burbujas totalmente naturales.

Una vez embotellada la kombucha y añadidos los ingredientes que nos gusten, se da comienzo a la segunda fermentación, también conocida como «carbonatación», que se produce sin presencia de oxígeno (fermentación anaeróbica). Durante esta etapa, las levaduras que quedan en la bebida consumen el azúcar que le hemos añadido y producen dióxido de carbono (CO2), que se disuelve en la bebida, creando las burbujas.

Es importante tener en cuenta que durante esta fase se produce una mayor cantidad de alcohol que en la primera fermentación, por lo que, si se deja fermentar demasiado tiempo, la kombucha podría volverse demasiado alcohólica. Por lo general, la segunda fermentación suele durar entre uno y cinco días, dependiendo de la temperatura ambiente y la cantidad de azúcar añadida.

It is important to note that a greater amount of alcohol is produced during this phase than in the first fermentation, so if left to ferment for too long, the kombucha could become too alcoholic. Typically, the second fermentation usually lasts between one and five days, depending on the ambient temperature and the amount of sugar added.

It is advisable to leave the kombucha in the second fermentation in a dark, room temperature place, as sunlight can negatively affect the fermentation process and alter the flavor of the drink. In addition, it is important to use pressure-resistant glass bottles, since the bubbles generated can increase the pressure inside the bottle and cause it to break.

Once the kombucha has reached the desired degree of carbonation, it can be refrigerated to stop the fermentation process and enjoy a fresh, bubbly drink with the flavor and healthy properties that we love. Kombucha is a very versatile drink that can be adapted to each person's tastes and experiment with different ingredients and flavors to make it even more special.

A trick to control the second fermentation of kombucha at home

If you ferment at home you will not have control of this second fermentation. Above all, because without equipment or analysis it is difficult to know the sugar level of the kombucha at the time of bottling. If there is too much sugar, the yeasts will begin to produce CO2, either until the sugar runs out or until the bottle holds and bursts.

One way to control the carbonation point at home is to use a used plastic soda bottle. At the time of bottling, if you press it you will see that it is loose, but as the days go by and the carbonation occurs you will see how it becomes harder and harder. This way you avoid having to open bottles to test the carbonation point. When you see that the sample bottle is hard enough, it is time to store your kombuchas in the refrigerator to stop this second fermentation.