Zoom in on microorganisms


The famous kefir grains

The famous kefir grains

© Ross McKay

Kefir grains are off-white or pale yellow, have an irregular shape similar to cauliflower buds, and a texture similar to tapioca pudding. A single grain may be up to 2 cm in diameter and weigh approximately 800 mg (1200 mg once immersed in milk). Each grain is composed of a matrix of kefiran (a type of sugar) and proteins which traps the live bacteria and yeasts that will eventually multiply.

The microbial composition of kefir grains depends on their country of origin. More than twenty bacterial species—including Lactobacillus kefirgranum, Lactobacillus kefir, Lactobacillus kefiranofaciens, Lactococcus lactis and species from the Leuconostoc. Several species of yeast—including Candida kefir, Kluyveromyces marxianus and Saccharomyces cerevisiae are also present.