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Kefir

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Grains of kefir
For the Islamic term, see Kaffir.

Kefir (alternately kephir, kewra, talai, mudu kekiya, milkkefir, búlgaros) is a fermented milk drink that originated in Central Asia's Turkic and Mongol peoples. It is prepared by inoculating cow, goat, or sheep's milk with kefir grains. Traditional kefir was made in skin bags that were hung near a doorway, and the bag was knocked by everyone passing through the doorway to help keep the milk and kefir grains well mixed.[1]

Kefir grains are a combination of bacteria and yeasts in a matrix of proteins, lipids, and sugars. This symbiotic matrix forms grains that resemble cauliflower. Today, kefir is becoming increasingly popular due to new research into its health benefits. Many different bacteria and yeasts are found in the kefir grains, which are a complex and highly variable community of micro-organisms.[2]

The traditional kefir product 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[3]. Kefir fermented by small-scale dairies early in the twentieth century achieved alcohol levels between 1% and 2%, but kefir made commercially with modern methods of production has less than 1% alcohol, possibly due to reduced fermentation time.[1]

Variations that thrive in various other liquids exist. They may vary markedly from kefir in both appearance and microbial composition. Water kefir (or kefir d'acqua) is grown in water with sugar, dry fruit such as figs, and lemon juice for a day or more at room temperature.

Making Kefir

Wikibooks Cookbook has a recipe/module on
90 grams of kefir grains

Production of traditional kefir requires kefir grains which are a gelatinous community of bacteria and yeasts. Kefir grains contain a water soluble polysaccharide known as kefiran that imparts a rope-like texture and feeling in one's mouth. Kefir grains cannot be produced from scratch, but the grains grow during fermentation, and additional grains are produced. Kefir grains can be purchased or acquired from other hobbyists, see below. Kefir grains appear white to yellow and are usually the size of a walnut, but may be as small as a grain of rice.

Care of kefir grains

When kefir grains are not in use they may be stored wet or dry. They can be stored wet up to 8 to 10 days in water at 4ºC. Alternatively they may be wrapped in cheese cloth and allowed to dry for 36 to 48 hours at room temperature, and these dried grains may be stored at room temperature in an envelope for 12 to 18 months. Dried kefir grains may be reactivated by several successive growth cycles in milk. The grains are ready for kefir production when the kefir they produce looks and smells like the original (wet) form. This re-growth stage is required to re-establish the correct bacterial balance within the culture.

Kefir grains may become contaminated with undesirable bacteria such as coliforms and other spoilage bacteria that shorten the kefir shelf-life. To guard against this, kefir-making containers should be washed and sanitized prior to making kefir. Suitable containers include glass jars such as jam jars or pickle jars, but any suitably sized glass container will work. When necessary to wash kefir grains they should be also washed in pre-boiled and chilled water or fresh milk. Use of chloraminated tap water should be avoided, but if necessary it should be de-chloraminated.

Production of Kefir

To make kefir, milk should be inoculated with kefir grains (5% w/w) and incubated until a smooth yoghurt-like consistency develops. This is generally 12 hours at 18 - 22ºC. Carbonated kefir may be produced by sealing the fermented product into beer bottles for ripening (1 to 3 days at 10ºC). Kefir should be kept out of direct sunlight. If you have no means to regulate the temperature of fermentation, then the top of a warm refrigerator or a cupboard above the stove are suitable places. In warm to hot climates, kefir may be produced by placing the fermentation vessel into the refrigerator during the day and on the counter top at night.

  1. Strain the prior day's kefir batch with a sanitized sieve.
  2. Return the grains to a sanitized glass jar. Add fresh pasteurized milk, and cover loosely.
  3. Enjoy the liquid kefir portion that went through the strainer.
  4. Leave the new batch to sit and ferment.

Available commercial starter cultures do not make traditional kefir. These starters contain selected bacteria and yeasts isolated from kefir grains and will not produce kefir grains. These starter cultures result in a more consistent product as opposed to traditional kefir which varies from batch to batch.

See also: kumis, ayran, lassi, tibicos and other dairy products.

Health Benefits

One can change the nutrient content by simply fermenting for shorter or longer periods. Both stages have different healthful benefits. For instance, kefir over-ripened (increases sour taste) significantly increases folic acid content.[4] Kefir also aids in lactose digestion, making it more suitable than other dairy products for those who are lactose intolerant.[5] The kefiran in kefir has been shown to suppress an increase in blood pressure and reduce serum cholesterol levels in rats.[6]

Drinking Kefir

While some drink kefir straight, many find it too sour on its own and prefer to add fruits, honey, maple syrup or other flavors or sweeteners. Frozen bananas, strawberries, blueberries or other fruits can be mixed with kefir in a blender to make a smoothie. Vanilla, agave nectar and other flavorings may also be added.

Different milk types

Kefir grains will successfully ferment the milk from most mammals, and will continue to grow in such milk. Typical milks used include cow, goat, and sheep, each with varying organoleptic and nutritional qualities.

In addition, kefir grains will ferment non-mammal "milks" such as soy milk, rice milk, and coconut milk, as well as other sugary liquids including fruit juice, coconut water, beer worts and ginger beer. However, the kefir grains may cease growing if the medium used does not contain all the growth factors required by the bacteria (which are all present in mammalian milk), so it is best to only use excess kefir grains for trying alternative fermentation media.

Milk sugar is, however, not essential for the synthesis of the polysaccharide that makes up the grains (kefiran), and scientific studies have demonstrated that rice hydrolysate is a suitable alternative medium.[7] Additionally, it has been shown that kefir grains will reproduce when fermenting soy milk, although they will change in appearance and size due to the differing proteins available to them.[8]

References

  1. ^ a b Farnworth, Edward R. (2003). Handbook of Fermented Functional Foods. CRC. ISBN 0-8493-1372-4.
  2. ^ Lopitz-Otsoa, F (2006). "Kefir: A symbiotic yeast-bacteria community with alleged healthy capabilities" (PDF). Revista Iberoamericana de Micología. 23: 67–74. Retrieved 2007-06-10. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ Kowsikowski, F., and V. Mistry. 1997. Cheese and Fermented Milk Foods, 3rd ed, vol. I. F. V. Kowsikowski, L.L.C., Westport, Conn.
  4. ^ Kneifel, W (1991). "Vitamin profiles of kefirs made from milks of different species". International Journal of Food Science & Technology. 26: 423–428. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  5. ^ Hertzler, Steven R. (2003 May). "Kefir improves lactose digestion and tolerance in adults with lactose maldigestion". Journal of the American Dietetic Association. 103 (5). Elsevier, Inc.: 582–587. doi:10.1053/jada.2003.50111. Retrieved 2007-06-10. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  6. ^ Maeda, H (2004-12-30). "Effects of an exopolysaccharide (kefiran) on lipids, blood pressure, blood glucose, and constipation". BioFactors. 22 (1–4). IOS Press: 197–200. Retrieved 2007-06-10. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  7. ^ Maeda, H (2004-08-25). "Structural characterization and biological activities of an exopolysaccharide kefiran produced by Lactobacillus kefiranofaciens WT-2B(T)". Journal of Agricultural and Food Chemistry. 52 (17). American Chemical Society: 5533–8. doi:10.1021/jf049617g. Retrieved 2007-06-10. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  8. ^ Abraham, Analía G. (May 1999). "Characterization of kefir grains grown in cows' milk and in soya milk". Journal of Dairy Research. 66 (2). Cambridge University Press: 327–333. doi:10.1017/S0022029999003490. Retrieved 2007-06-09. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
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