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KEFIR - A MULTI-CULTURAL FERMENTATION |  | ||||||||
 | Dutiful yeasts The Danish dairy firm Christian Hansen set up a laboratory for the manufacture of rennet for cheese production in Reading in 1913. Chr. Hansen's closed its doors several years ago, but when the NCBE first became interested in kefir in the late 1980s, the firm imported real kefir grains from Denmark - if you paid the duty (Denmark was not then part of the EEC). Strangely, duty was only paid on the yeasts in the culture - not on the bacteria! |  | |||||||
Kefir (or kefyr) is an unusual fermented drink which originated in Eastern Europe. It is made by adding a special mixed culture of bacteria and lactose-fermenting yeasts to milk. Some of the bacteria are not unlike those used for making yoghurt, while the yeasts generate carbon dioxide and a small amount of alcohol. Other bacteria produce a viscous gum which holds all the microorganisms together in gelatinous lumps. This allows the kefir 'grains' to be separated from the milk and re-used once the fermentation is through. The finished product is like a refreshing, fizzy, drinking yoghurt. A wide range of lactic acid bacteria are involved in the fermentation, including Lactobacillus casei, L. acidophilus and Streptococcus lactis, which produce mainly lactic acid from the lactose in the milk. Flavour components are produced by Lactobacillus bulgaricus which produces acetaldehyde, Leuconostoc cremoris, diacetyl and acetonin, and Lactobacillus brevis, which produces acetonin, acetic acid and ethanol, as well as carbon dioxide. The yeasts Candida kefyr (also known as Saccharomyces kefir, S. lactis or Torulopsis kefir) and Kluyveromyces fragilis (K. lactis) convert lactose to ethanol and carbon dioxide during the cooler ripening period. Unfortunately, kefir grains are not readily available in the UK and are expensive to import. This practical exercise presented a cheaper alternative which yields a similar product to real kefir - well, sort of. | |||||||||
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