Make sure to leave some head space in your jar of fermenting coconut water.
As the bacteria in your culture eat the sugars in the coconut water, gasses are created. These gasses have to go somewhere, hence the pocket of air at the top of your jar.
How tight to put the lid on?
There is a fine line between tight enough to trap most of the gasses so your drink has some fizz to it and not so tight that you have a dangerous buildup of gasses that could cause your jar to explode. Error on the side of not too tight, check it within 18 hours and don’t ferment longer than 48 hours.
To strain or not to strain?
When using milk kefir grains, I do not strain them, but instead place the jar I fermented in directly into the refrigerator, grains and all.
The coolness of the refrigerator slows down fermentation and the grains live off the residual sugar in the coconut water. This is why I stop fermentation when there is still some sweetness in the water.
You can also pour your fermented coconut water through a strainer and store your kefir grains in a small jar of sugar water kept in the refrigerator. This is an extra step I don’t care to take, but you may prefer to do so.
Three variables to look at as your adjust your fermentation:
Sweetness of the coconut water. The sweeter the coconut water the faster fermentation will proceed. The more sugar you feed the bacteria the faster they will work for you.
Taste amount of sweetness in coconut water before ferment, so you understand this variable.
Ambient Temperature. The warmer the area in which you’re fermenting, the faster fermentation will proceed. In summer, my coconut water ferments in 12 hours, whereas in winter it may take 24 hours.
Fermentation Length. The longer you ferment your coconut water the less sweetness there will be. I like a tad of sweetness to my finished ferment, so I ferment for a shorter period of time.
Home too cool?
If your home is too cool and it is taking longer than 48 hours for your coconut water to ferment, your can either wrap the jar in a blanket or set it on a heating pad (monitor carefully) to give the bacteria a little more heat to do their work. Ideal fermentation temperature is 68-72°F (20-22°C).
Want to make a larger batch?
The recipe I give is for 1 quart, but I usually make one-half gallon which lasts a week in my household. I use closer to 1/2 cup of water kefir grains and 3 cans of 520 ml coconut water which fits nicely in the tall half-gallon canning jars.
To wash or not to wash your fermentation jar between batches?
I don’t wash my fermentation jar with every batch. The bacteria in the culture are creating a perfect environment for the fermentation process and the less I mess with it the better, I feel.
So, I only wash the jar every 5 or 6 batches when the jar gets too dirty or when there is a build-up of residue on the bottom of the jar.
White gunk building up on the bottom of your jar?
This is just sediment from the coconut water and nothing to worry about.
Coconut water not fermenting?
Try a different brand of coconut water, perhaps a raw coconut water. Pasteurized coconut water does not always ferment easily and maybe the brand you’re using is pasteurized by high heat for a longer time than the flash-pasteurized brands.
Make sure you are fermenting at a warm enough temperature (68-72°F, 20-22°C).
Play around with your ratio of grains to water. The greater the proportion of grains the faster the coconut water will ferment.
Keep an ear tuned for the sound of gas escaping your jar, which indicates fermentation is happening.
Coconut water turning to alcohol?
Reduce the amount of grains and/or the length of time you're fermenting. Water kefir grains grow so rapidly that you'll have to regularly reduce the amount. You won't have this issue with milk kefir grains which grow much more slowly.
If the fermentation process has not started within 48 hours, toss the coconut water, troubleshoot and try again.
Coconut water is a perishable product. Without a working culture, it is not fermenting but degrading as it sits on your counter.
NOTE: If you are using yogurt whey as your culture, it can take up to 4 days. You’re fine to leave it that long as long as you detect a shift in sweetness and a bit of fizz starting within 48 hours.
Store finished ferment in the refrigerator.
And, don’t leave a sealed bottle out of the refrigerator for too long. Fermented coconut water is alive and will continue to ferment, eating the sugars and creating a buildup of gasses that have to go somewhere. This happens very slowly in your refrigerator and rather fast in a hot car. Though I keep a bottle in my car on a driving trip, I’m opening it throughout the day, which allows the gasses to whoosh out.