Kefir

Kefir(/kəˈfɪər/kə-FEER;alternative spellings:kephirorkefier;Russian:кефир[kʲɪˈfʲir];Karachay-Balkar:гыпы) is afermented milk drinksimilar to a thinyogurtorayranthat is made from kefir grains, a specific type ofmesophilicsymbiotic culture. It is prepared byinoculatingthe milk ofcows,goats, orsheepwith kefir grains.
Kefir is a common breakfast, lunch or dinner drink consumed in countries of westernEurasia. Kefir is consumed at any time of the day, such as alongside European pastries likezelnik(zeljanica),burekandbanitsa/gibanica, as well as being an ingredient in cold soups.
Kefir has been found in graves in the Bronze AgeXiaohe Cemetery, dating back 3,600 years.The wordkefir, known in Russia, Central European and Eastern European countries since at least 1884,is of North Caucasian origin.A Russian borrowing in English, its ultimate origin is unknown, though one theory is that the word comes fromköpürinOld Turkic.More likely is another Caucasian origin; compareGeorgianკეფირი(k’epiri),Mingrelianქიფური(kipuri),Ossetianкъӕпы(k’æpy), andKarachay-Balkarгыпы(gıpı). Theptoftransformation may indicate possible transmission to Russian throughArabicكِفِير(kifīr), which would have served as a lingua franca in the Muslim parts of the Caucasus.
Traditional kefir was made ingoatskinbags that were hung near a doorway; the bags would be knocked by anyone passing through to keep the milk and kefir grains well mixed.In Karachay-Balkar,gıpıhas a connection withgıpıt(wineskin). It was under the namewineskinthat Karachay kefir was distributed in the second half of the 19th century and at the beginning of the 20th century.Kefir spread from the former Soviet Union to the rest of Europe, Canada, Japan, and the United States by the early 21st century.It has become known in parts ofLatin Americaasbúlgaros, or "Bulgarians".
The homeland of kefir is considered to be "the vicinity ofElbrus, along the upper reaches of theKuban".
Traditional kefir is fermented at ambient temperatures, generally overnight. Fermentation of the lactose yields asour,carbonated, slightly alcoholic beverage, with a consistency and taste similar to drinkableyogurt.
The kefir grains initiating the fermentation are initially created by auto-aggregations ofLactobacillus kefiranofaciensandMaudiozyma turicensis,where multiplebiofilmproducers cause the surfaces to adhere which form a three dimensional microcolony.The biofilm is amatrixofheteropolysaccharidescalled kefiran, which is composed of equal proportions ofglucoseandgalactose.It resembles smallcauliflowergrains, with color ranging from white to creamy yellow. A complex and highly variable symbiotic community can be found in these grains, which can includeacetic acid bacteria(such asAcetobacter acetiandA. rasens), yeasts (such asCandida kefyr,Saccharomyces cerevisiae,M. turicensis) and a number ofLactobacillusspecies, such asL. parakefiri,L. kefiranofaciens(and subsp.kefirgranum),L. kefiri,etc.While some microbes predominate,Lactobacillusspecies are always present.The microbe flora can vary between batches of kefir due to factors such as the kefir grains rising out of the milk while fermenting or curds forming around the grains, as well as temperature.Additionally, Tibetan kefir composition differs from that of the Russian kefir, Irish kefir, Taiwan kefir and Turkeyfermented beveragewith kefir.In recent years, the use offreeze-driedstarter culture has become common due to stability of the fermentation result, because the species of microbes are selected in laboratory conditions, as well as easy transportation.
During fermentation, changes in the composition of ingredients occur.Lactose, the sugar present in milk, is broken down mostly tolactic acidby the lactic acid bacteria, which results in acidification.Propionibacteriafurther break down some of the lactic acid intopropionic acid(these bacteria also carry out the same fermentation inSwiss cheese). Other substances that contribute to the flavor of kefir arepyruvic acid,acetic acid,diacetylandacetoin(both of which contribute a "buttery" flavor),citric acid,acetaldehyde, andamino acidsresulting from protein breakdown.
During the fermentation process, bacteria and yeast break lactose down into glucose and galactose.As a result of the fermentation, lactose levels are decreased by 20–30% with respect to the initial lactose levels present in the milk.One study found that when people withlactose intoleranceconsumed the same amount of lactose in milk, kefir oryogurtproducts, the latter two showed significantly reduced symptoms of lactose intolerance during the first 8 hours after consumption.This result suggests that yoghurt and kefir might be suitable for people with lactose intolerance. However, the long-term impact of kefir consumption on lactose intolerance has not been studied. It has also been shown that fermented milk products have a slower transit time than milk, which may further improve lactose digestion.
Kefir containsethanol.The level of ethanol in kefir can vary by production method. A 2016 study of kefir sold in Germany showed an ethanol level of only 0.02 g per litre, which was attributed to fermentation under controlled conditions allowing the growth ofLactobacteriaonly, but excluding the growth of other microorganisms that form much higher amounts of ethanol.A 2008 study of German commercial kefir found levels of 0.002–0.005% of ethanol.Kefir produced by small-scale dairies in Russia in the early 20th century had 1–2% ethanol.
Kefir products contain nutrients in varying amounts from negligible to significant, includingdietary minerals,vitamins,essential amino acids, andconjugated linoleic acid,At a pH of 4.2 – 4.6,kefir is composed mainly of water and by-products of the fermentation process, includingcarbon dioxideandethanol.
Several dietary minerals are found in kefir, such ascalcium, iron,phosphorus,magnesium,potassium,sodium, copper,molybdenum,manganese, andzincin amounts that have not been standardized to a reputable nutrient database.Kefir contains vitamins in variable amounts, includingvitamin A,vitamin B1(thiamine),vitamin B2(riboflavin),vitamin B3(niacin),vitamin B6(pyridoxine),vitamin B9(folic acid),vitamin B12(cyanocobalamin),vitamin C,vitamin D, andvitamin E.Essential amino acids found in kefir includemethionine,cysteine,tryptophan,phenylalanine,tyrosine,leucine,isoleucine,threonine,lysine, andvaline.
Probioticbacteria found in kefir products include:Lactobacillus acidophilus,Bifidobacterium bifidum,Streptococcus thermophilus,Lactobacillus delbrueckii subsp. bulgaricus,Lactobacillus helveticus,Lactobacillus kefiranofaciens,Lactococcus lactis, andLeuconostocspecies.Lactobacilliin kefir may exist in concentrations varying from approximately 1 million to 1 billioncolony-forming unitsper milliliter, and are the bacteria responsible for the synthesis of the polysaccharidekefiran.
In addition to bacteria, kefir often contains strains ofyeastthat can metabolize lactose, such asKluyveromyces marxianus,Kluyveromyces lactis, andSaccharomycesfragilis, as well as strains of yeast that do not metabolize lactose, includingSaccharomyces cerevisiae,Torulaspora delbrueckii, andKazachstania unispora.The nutritional significance of these strains is unknown.
Modern kefir is made by adding kefir grains to milk typically at a proportion of 2–5% grains-to-milk. The mixture is then placed in a corrosion-resistant container, such as a glass jar, and stored preferably in the dark to prevent degradation of light-sensitive vitamins. After a period between 12 and 24 hours of fermentation at mild temperature, ideally 20–25 °C (68–77 °F),the grains are strained from the milk using a corrosion-resistant (stainless steel or plastic) utensil and kept to produce another batch. During the fermentation process the grains enlarge and eventually split forming new units.
The resulting fermented liquid may be drunk, used in recipes, or kept aside in a sealed container for additional time to undergo a secondary fermentation. Because of its acidity the beverage should not be stored in reactive metal containers such as aluminium, copper, or zinc, as these may leach into it over time. The shelf life, unrefrigerated, is up to thirty days.
The Russian method permits production of kefir on a larger scale and uses two fermentations. The first step is to prepare the cultures by inoculating milk with 2–3% grains as described. The grains are then removed by filtration and 1–3% of the resulting liquid mother culture is added to milk and fermented for 12 to 18 hours.
Kefir can be made usingfreeze-driedcultures commonly available in powder form fromhealth food stores. A portion of the resulting kefir can be saved to be used a number of times to propagate further fermentations but ultimately does not form grains.
In Taiwan, researchers were able to produce kefir in a laboratory using microorganisms isolated from kefir grains. They report that the resulting kefir drink had chemical properties similar to homemade kefir.
Kefir grains will ferment the milk from mostmammalsand will continue to grow in such milk. Typical animal milks used include cow, goat, and sheep, each with varyingorganoleptic(flavor, aroma, and texture) and nutritional qualities.Raw milkhas been traditionally used.
Milk sugaris not essential for the synthesis of the polysaccharide that makes up the grains (kefiran), and rice hydrolysate is a suitable alternative medium.Additionally, kefir grains will reproduce when fermenting soy milk, although they will change in appearance and size due to the differing proteins available to them.
A variation of kefir grains that thrive in sugary water also exists, seewater kefir(ortibicos), and can vary markedly from milk kefir in both appearance and microbial composition.
As it containsLactobacillusbacteria, kefir can be used to make asourdoughstarter.It is also useful as abuttermilksubstitute inbaking. Kefir is one of the main ingredients incold borschtsoup inLithuania, also known in Poland asLithuanian cold soup(chłodnik litewski), and other countries. The kefir-based soupokroshkais common across the formerSoviet Union. Kefir may be used in place of milk on cereal,granola,milkshakes,saladdressing,ice cream,smoothiesandsoup.
InEstonia, kefir is also often mixed withkamaand eaten as a snack or a quick breakfast.