Water kefir grains

A community held in a gel

Water kefir grains are polysaccharide aggregates, translucent clumps of gel that carry a mixed microbial community. Studies of grains from several sources report lactic-acid bacteria and yeasts, with other groups in some samples. The grains are fed sugar water, and the community ferments it into a lightly sparkling, sour drink that can also contain some ethanol.

The community is not a fixed list. Species and their abundance vary between grain sources, which is why a name such as tibicos, tibi, sugary kefir or Japanese water crystals does not identify the lineage in a particular jar. Water kefir is also a different culture from dairy milk kefir.

Grain and liquor are different phases

The gel matrix and the fermented liquid around it are not the same thing. Some microorganisms move into the liquid, but a time-course study found that most of the sampled ecosystem stayed with the grains. The liquor can be used as an inoculum in some processes, but that alone does not show that the grain structure or its community is being reproduced.

Water chemistry in one experiment

An eight-step laboratory study that transferred grains through repeated fermentations found that the water's buffer capacity and calcium concentration were associated with grain growth, pH, carbohydrate use and the products formed. The grain inoculum and the prepared media were specific to that experiment, so its thresholds are not a general mineral formula for household water and do not indicate safety.

Names and origin

Two accounts of where water kefir comes from circulate. One is a nineteenth-century British ginger-beer plant history, linked to soldiers returning from the Crimea; the other is Mexican Tibi grains associated with Opuntia cactus. The origin is unresolved. Sampling from several countries shows how widely the grains have been studied, not that they share one birthplace or ancestry, and cultures sold under overlapping names should not be assumed to be the same.

Using the grains, and what the sources do not say

The drink made with the grains has its own page, which carries a method; this page does not repeat one. Water kefir can produce ethanol and carbon dioxide, and public-health guidance from British Columbia discusses these within its own food-safety framework. Bubbles, sourness, smell, taste or visible growth cannot establish safety or measure the alcohol content.

The sources reviewed give no feed ratios, schedule, bottling method, storage period, revival method or household safety limit for grains, and the British Columbia guidance reflects its own jurisdiction.