Fermented drinks such as water kefir and kombucha and ginger beer are fun and very easy to make and drink. The bacteria and yeast in the cultures converts the sugars into lactic acid, a very small amount of alcohol, and a lot of carbon dioxide. In some cases too much carbon dioxide, and as the drink continues to ferment, more and more gas is created. This gas creates pressure when it is sealed into a bottle and the more gas that is created the more pressure is created, and too much can cause problems.
SO WHAT FACTORS AFFECT BOTTLED WATER KEFIR PRESSURE?
Kefir goes through two fermentation periods and both are essential to a successful carbonated beverage. During the first period, water kefir grains need enough minerals, sugar, and clean water to be healthy. Once the grains are removed, there is not likely to be a lot of fizz just with the basic ingerdients. Adding just a small amount of sugar, either as sugar or from fruits and fruit juices can get things more lively. Do remember the more sugar, the more it will ferment therefore the more gas it will create and more pressure.
The pressure of water kefir can be significant, underestimate it at your peril so choosing high quality bottles is of the utmost importance. Look for a bottle that is heavy for its size, with thick glass. The bale (or wires) on the swing top should be heavy guage and not bend with pressure. The rubber gasket should be pliable and fit snugly. We strongly recommend using fermenting bottles as they really do need to be able to withstand the pressure. NEVER re-use wine bottles or standard glass bottles and they are not suitable for fizzy drinks. Please also be aware that not all swing top bottles are fermenting bottles so always double check that they are suitable for the pressure.
You should always check that your bottles for cracks, chips, splits or flaws every time you use them and never use a bottle that has any of these. they should be discarded and a new one used.
Time and Temperature
At warmer temperatures, the kefir will ferment much faster. So in the summer months you will get much more fizz. We recommend burping (opening the bottle to release pressure) once a day under normal conditions (please see our article on how to do this) . If temperatures are over 24C, it may be necessary to burp bottles more frequently or store the bottles with something that allows them to breathe (ie cloth or kitchen paper secured with a rubber band). Once refrigerated, chilled bottles should be burped weekly.
SAFETY WHEN BOTTLING WATER KEFIR
It can be a little daunting to go back to making fizzy kefir once a bottle explodes. To contain the bottles and ease the nerves, place fermenting bottles in a box or other container (i find the fridge bags you can get at the supermarket very handy for this, it won't stop the bottle exploding but it will contain the mess if they do)
If a full bottle has not been burped for awhile, take it outside and cover with a dishtowel or hand towel. Wrap it up and point the top of the bottle away from faces or anything breakable. Use the towel to help pry the bale out and up. The towel will absorb any excess soda.
Personally i always try to open my water kefir over the sink (just in case) and have a plastic jug handy to pop over the top of the bottle in case you get a fountain (saves repainting the ceiling).
Kefir is delicious, nutritious and a great alternative to commercial sodas. Exercise a little caution and common sense to enjoy the bubbles in your glass instead of on the ceiling.