No carbonic acid forms.Updated a year ago

To produce fizzy milk kefir, it is important to use a tightly closed fermentation vessel so that the CO2 cannot escape. 

Further carbonic acid can also be produced during a secondary fermentation. To do this, the finished milk kefir is filled into tightly closed bottles and left to ferment for another 1-2 days at room temperature. Bottles with swing tops, for example, are well suited for this. Now the following happens: The yeasts continue to produce carbon dioxide, which in turn reacts with water under pressure to form carbonic acid. The result: milk kefir with fizz.