Kefiran is the clear or pale yellow polysaccharide

Polysaccharide

Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

 gel exuded by dairy

Dairy

A dairy is a business enterprise established for the harvesting of animal milk—mostly from cows or goats, but also from buffalo, sheep, horses or camels —for human consumption. A dairy is typically located on a dedicated dairy farm or section of a multi-purpose farm that is concerned...

 kefir

Kefir

Kefir is a fermented milk drink that originated with shepherds of the North Caucasus region, who discovered that fresh milk carried in leather pouches would occasionally ferment into an effervescent beverage...

 or water kefir grains.

Dairy kefir grains are symbiotic consortia of bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 and yeasts which ferment milk containing the complex sugar lactose

Lactose

Lactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk , although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from or , the Latin word for milk,...

, whereas water kefir grains contain less microbial diversity and can be cultured in water and sugar alone. Kefiran has been shown to exhibit certain medicinal qualities, and it contributes to the organoleptic (mouthfeel

Mouthfeel

Mouthfeel is a product's physical and chemical interaction in the mouth, an aspect of food rheology. It is a concept used in many areas related to the testing and evaluating of foodstuffs, such as wine-tasting and rheology. It is evaluated from initial perception on the palate, to first bite,...

) qualities of kefir. Bacteria that produce kefiran have been identified as Lactobacillus kefiranofaciens and Lactobacillus delbrueckii subsp. bulgaricus

Lactobacillus bulgaricus

Lactobacillus delbrueckii subspecies bulgaricus is one of several bacteria used for the production of yogurt. It is also found in other naturally fermented products...

.