Zoom in on microorganisms

Kefir

KefirZoomZoom
© Miloslav Kalab, Agriculture and Agri-Food Canada, Ottawa
The famous kefir grains ZoomZoom
© Ross McKay
Kefir makingMovie ClipMovie Clip
© Production Cinémanima inc. and Armand-Frappier Museum

Kefir, The champagne of Dairy Products

Kefir is fermented milk obtained through the action of certain bacteria and yeast. Because they remain alive these microorganisms continue to produce carbon dioxide in the final product, which explains the characteristic containers used to package kefir. Carbon dioxide also accounts for the tingling sensation reminiscent of champagne experienced when eating kefir.

How Is Kefir Made?

First, grains of kefir are added to partially skimmed cow's milk. Over the next twenty-four hours, bacteria and yeast present in the kefir grains cause the milk to ferment, making it more acid (lowering its pH) and changing its texture and composition. Carbon dioxide is also produced. Following incubation and maturation, the grains are separated from the culture medium, which is added to a fermenting chamber containing pasteurized milk. The inoculated pasteurized milk is left to incubate and mature, and is transformed into kefir, which is sold plain or with fruit added to it. Kefir continues to produce carbon dioxide until it is consumed, and its packaging takes this into account. Kefir containers are sealed with a sheet of aluminum that stretches as carbon dioxide is produced, and have large lids designed to accommodate this expansion.