Overview
The term kefir, existing in modern Russian since 1884 and English, probably ultimately from Arabic Keif and has become the most commonly used name, although it is known in other regions by various names. Kefir grains are a combination of bacteria and yeasts in a matrix of proteins, lipids, and sugars, and this symbiotic matrix forms "grains" that resemble cauliflower. For this reason, a complex and highly variable community of lactic acid bacteria and yeasts can be found in these grains.
Kefir grains contain a water-soluble polysaccharide known as kefiran, which imparts a rope-like texture and feeling in the mouth; it ranges in color from white to yellow, and may grow to the size of walnuts.
Constituents of kefir:
- Micro-organisms: lactic acid bacteria, yeasts
- Fermentation Products: carbon dioxide, ethanol (alcohol)
- Nutrients: protein from milk, polysaccharide
- Vitamins or pro-vitamins: vitamin A, vitamin B1, vitamin B2, vitamin B6, vitamin D, folic acid, nicotinic acid
- Minerals: calcium, iron, iodine
- Water
The composition of kefir depends greatly on the type of milk that was fermented, including the concentration of vitamin B12. During the fermentation, changes in composition of nutrients and other ingredients have also been shown to occur. Lactic acid is the organic acid in highest concentrations after fermentation and is derived from approximately 25% of the original lactose in the starter milk. Research has shown, however, that lactose maldigestors are able to tolerate kefir, providing the number of live bacteria present in this beverage consumed is high enough. It is believed that the bacteria in the kefir or yoghurt matrix are protected by the buffering effect of the yoghurt. It has also been shown that fermented milk products have a slower transit time than milk, which may further improve lactose digestion
For the preparation of the present factory-produced kefir, the so-called kefir mild, kefir grains are no longer used, but a precise composed mixture of different bacteria and yeast, allowing the flavor to be kept constant.
Traditional kefir is fermented at ambient temperatures, generally overnight. Fermentation of the lactose yields a sour, carbonated, slightly alcoholic beverage, with a consistency similar to thin yogurt. Kefir fermented by small-scale dairies early in the 20th century achieved alcohol levels between one and two percent, but kefir made commercially with modern methods of production has less than 1% alcohol, possibly due to reduced fermentation time.
Variations that thrive in various other liquids exist, and they vary markedly from kefir in both appearance and microbial composition. Water kefir (or kefir d'acqua) is grown in water with sugar (sometimes with added dry fruit such as figs, and lemon juice) for a day or more at room temperature.
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