BY: Camila Costa

What is the purpose of a second ferment?

Fermenting water kefir a second time, also known as the secondary fermentation or bottling stage, serves a few important purposes.


The primary purpose of the secondary fermentation is to carbonate the water kefir. During the first fermentation stage, the water kefir grains consume the sugars and produce various compounds, including carbon dioxide. In the secondary fermentation, when the water kefir is bottled in an airtight container, the remaining sugars are further fermented by the residual yeast, resulting in the production of additional carbon dioxide. This process creates the desired fizzy and carbonated texture in the water kefir.

Flavor Enhancement

The secondary fermentation stage allows for the development of more complex and well-rounded flavors in water kefir. The extended fermentation time allows the flavors to meld and mature, resulting in a more balanced taste profile. Additionally, flavors can be enhanced during this stage if additional ingredients, such as fruits, herbs, or spices, are added to the fermentation vessel.


The secondary fermentation also aids in the clarification of the water kefir. As the water kefir sits undisturbed in the bottle, any sediment or cloudiness present in the liquid can settle at the bottom. This helps to produce a clearer and visually appealing final product.

It’s important to note that not all water kefir recipes require a second fermentation. Some recipes may call for a single fermentation, where the water kefir is consumed immediately after the initial fermentation stage. However, many people enjoy the additional carbonation and flavor development achieved through the secondary fermentation process.

During the secondary fermentation, it’s crucial to use appropriate fermentation vessels, such as swing-top bottles or other airtight containers, to trap the carbon dioxide produced and build up pressure. Regularly “burping” the bottles to release excess gas is necessary to prevent overcarbonation or bottle explosions. The duration of the secondary fermentation can vary depending on personal preference, but typically ranges from a few hours to a couple of days at room temperature. Refrigerating the water kefir after the desired carbonation level is reached can help slow down fermentation and maintain the carbonation levels.

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