Granos tibicos (water kefir)
Granos tibicos/water kefir grains is a biofilm culture of bacteria and yeast which is used to produce fermented beverages. The microbes coexist in a symbiotic relationship resulting in a relatively stable culture. The matrix of the grains is formed by polysaccharide dextran which is produced by bacteria Lactobacillus brevis. The colour of the grains vary from transparent to milky, the shape is irregular generally around 5 mm in diameter. The liquid used to feed the microbial culture includes variety of sugars, in Central and South America’s dark residual sugars like panela are used, the other ingredients vary greatly. During the fermentation lactic acid, ethanol and carbon dioxide are being produced. With just 24-48 hours necessary for the fermentation the beverage can be considered “quick ferment” compared to for example kombucha or milk kefir beverages which take around a week of fermentation. The resulting ferment is very light, somehow metallic flavoured beverage which is highly sparkling. Because of the minimal flavour of it’s own it is optimal base for flavouring, very refreshing especially during the summer and is very good for rehydratation.
The microbes present in the culture vary depending from culture to culture (which are nearly never alike) but generally comprise mixture of Lactobacillus, Streptococcus, Pediococcus and Leuconostoc bacteria and Saccharomyces, Candida, Kloeckera and others.
Interesting but possibly not confirmed:
Supposedly the tibicos grains are consisting of two layers, outer in which the bacteria and yeast are embedded (or attached to) and inner “sponge” like in which the carbon dioxide is accumulated (citation needed).