This review presents the most recent advances about kefir and kefiran, their production and microbial cultures involved, biological activities and potential applications in health and food industries. Kefir grains have a complex composition of microbial species such as the predominance of lactic acid bacteria, acetic bacteria, yeasts, and fungi Jianzhong et al. This microbial species are classified into four groups: homofermentative and heterofermentative lactic acid bacteria and lactose and non-lactose assimilating yeast Cheirsilp and Radchabut, In that way, Lactobacillus paracasei ssp.
Acetobacter aceti and A. More than 23 different yeast species have been isolated from kefir grains and from fermented beverages of different origins.
However, the predominant species are Saccharomyces cerevisiae, S. TABLE 1. Microbial compositions found in kefir and kefir grains of different origins.
The microbial composition may vary according to kefir origin, the substrate used in the fermentation process and the culture maintenance methods. Tibetan kefir, which is used in China, is composed of Lactobacillus, Lactococcus , and yeast. Additionally, acetic acid bacteria have been identified in Tibetan kefir, depending on the region in China from where it was obtained Gao et al. Wang et al. There are little information about the mechanism of grain formation, so the same authors, proposed a hypothesis to explain that.
The biofilm producers, Lactobacillus kefiri , Kluyveromyces marxianus HY1, and Pichia fermentans HY3 then adhere to the surface of these small granules due to their cell surface properties and their strong aggregation ability, which gives rise to thin biofilms. After biofilm formation, the kefir yeasts and Lactobacillus continue to co-aggregated with the granule strains and associate with the granule biofilm to become a three dimensional microcolony. As the cell density due to the growth of kefir yeasts and Lactobacillus increases, cells and milk components that are present in the liquid phase accumulate on the granule surface and the kefir grains are formed.
There is a symbiotic relation between the microorganisms present in kefir grains, wherein the bacteria and yeast survive and share their bioproducts as power sources and microbial growth factors.
This microorganism association is responsible for lactic and alcoholic fermentation Witthuhn et al. Table 1 demonstrates the microbial composition, which has been isolated from kefir and kefir grains of different origins. Due to its composition, kefir is mainly considered a probiotic resource Nalbantoglu et al.
Another reason for the increased interest in probiotic strains from kefir is its capacity to lower cholesterol levels. There are different ways in which bacteria can alter serum cholesterol: i through the binding to and absorption into the cell before it can be absorbed into the body; ii producing free and deconjugating bile acids; iii inhibiting the enzyme HMG-CoA reductase Yanping et al. The microorganisms in the kefir grains produce lactic acid, antibiotics and bactericides, which inhibit the development of degrading and pathogenic microorganisms in kefir milk Liu et al.
Kefir acts against the pathogenic bacteria Salmonella, Helicobacter, Shigella, Staphylococcus, Escherichia coli, Enterobacter aerogenes, Proteus vulgaris, Bacillus subtilis, Micrococcus luteus, Listeria monocytogenes, Streptococcus pyrogenes , Lopitz et al. On the other hand, it has been demonstrated that a mixture of kefir isolated bacteria and yeast is able to prevent diarrhea and enterocolitis triggered by Clostridium difficile Bolla et al. Besides, kefir showed good efficacy in inhibiting spore formation and aflatoxin B1 produced by the fungus Aspergillus flavus , which is a toxic compound formed either in the field or during food storage.
Therefore, kefir appears as a promising safe alternative natural food preservative offering protection against intoxication with aflatoxin B1 Ismaiel et al. It had been proved that many species of lactobacilli present in kefir have S-layer proteins. Surface layers S-layers can be aligned in unit cells on the outermost surface of many prokaryotic microorganisms Mobili et al.
However, there are other important bioactivities that have been tested with kefir grains, the cell-free fraction of kefir or acid lactic bacteria isolated from kefir, such as antitumoral Gao et al. In that way, it had been demonstrated that kefir cell-free fraction has antiproliferative effects on human gastric cancer SGC cells Gao et al.
Nevertheless, there are other important studies performed with some microorganisms isolated from different types of kefir. Some microorganisms with their biological activities and origin are shown in Table 2. The increased search for natural polysaccharides has been very significant due to their use in the food, pharmaceutical, and cosmetic industries as additives, bio-absorbents, metal removal agents, bioflocculants, and medicine delivery agents, among other functions De Vuyst et al. The polysaccharides that are commonly used as food additives are xanthan, dextran, gellan, and alginates, while the exopolysaccharides EPSs produced by lactic acid bacteria show good physicochemical characteristics for their use as food additives.
In addition to these characteristics, EPSs are obtained from microorganisms classified as GRAS generally recognized as safe , such as lactic acid bacteria Wang et al. Many reports have demonstrated that the quantity and properties of EPSs depend on the microorganisms used in the fermentation process and on the fermentation conditions and the composition of the culture media Kim et al. EPSs have physicochemical and rheological properties that make them suitable as additives, which can be used as stabilizers, emulsifiers, gelling agents, and viscosity improvers.
Additionally, EPSs possess biological properties suggesting their use as antioxidants, antitumor agents, antimicrobial agents, and immunomodulators, among other roles Suresh Kumar et al. These microorganisms grow in kefiran, which is a polysaccharide matrix consisting of glucose and galactose.
Despite good kefiran production by L. Lactic acid bacteria can synthesize homopolysaccharides or heteropolysaccharides. The synthesized homopolysaccharides are glucans or fructans, which are composed of only one type of monosaccharide glucose or fructose, respectively; Van Hijum et al. Similarly to lactic acid bacteria, Lactobacillus sp. The homopolysaccharides show a much higher performance compared with heteropolysaccharide production Welman and Maddox, ; Badel et al.
The heteropolysaccharides excreted by Lactobacillus delbrueckii , Lactobacillus bulgaricus , Lactobacillus rhamnosus , and Lactobacillus helveticus contain galactose, glucose, and rhamnose as the main monosaccharides, with other monosaccharides being present in smaller concentrations.
They are also highly branched with different types of linkages, and their denominations are complex and generally dependent on the main monosaccharide De Vuyst and Degeest, ; Badel et al. Lactobacillus plantarum isolated from Tibetan kefir excretes EPS classified as heteropolysaccharides composed of galactose, glucose, and mannose.
Kefiran is an EPS classified as a heteropolysaccharide comprising glucose and galactose in high concentrations, and it is classified as a water-soluble glucogalactan, which makes it suitable to be used as an additive Wang et al.
Kefiran has excellent rheological properties and can significantly improve the viscosity of lacteous products by favoring and maintaining gel properties and avoiding the loss of water during storage Rimada and Abraham, With respect to the biological activity of kefiran, several studies have demonstrated that this EPS can be used as a nutraceutical, as described in Table 3.
The first study about kefiran structure was published by Kooiman , who proposed a structure composed of two units: kefiran polysaccharide and kefirose pentasaccharide. Then, some authors analyzed the polysaccharide structure with current techniques such chromatography and infrared spectroscopy Wang et al. The kefiran structure, according to them, is shown in Figure 1. Nowadays, the interest in developing functional foods is increasing because people want to improve their health and prevent diseases.
Keeping in mind that kefir is a beverage with high probiotic activity, among other bioactivities, new companies are emerging around the world. One of the biggest kefir companies known is Lifeway, which started in ; their products can be obtained in the United States, Canada, and Great Britain, all of them based in kefir beverages, frozen, and cheese.
Table 4 summarizes the products provided these companies with some general information about each one. Kefir, the traditional beverage, is now recognized as a potential source of probiotics and molecules with highly interesting healthy properties.
The careful and detailed characterization of kefir composition has helped the scientific community to find new possibilities for its application. Kefiran, the EPS of kefir, has very important physicochemical and rheological properties. Besides, its biological properties suggest its use as antioxidant, antitumor agent, antimicrobial agent, and immunomodulator, among other roles.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Ahmed, Z. Kefir and health: a contemporary perspective. Food Sci. Altay, F. A review on traditional Turkish fermented non-alcoholic beverages: microbiota, fermentation process and quality characteristics.
Food Microbiol. Anselmo, R. Spanish Antagonistic effect of the kefir on endospores and vegetative cells of Bacillus cereus and Clostridium perfringens. Google Scholar. Badel, S. New perspective for Lactobacilli exopolysaccharides. Bensmira, M. Effects of fermentation conditions and homogenization pressure on the rheological properties of Kefir. Bolla, P. Protective effect of a mixture of kefir-isolated lactic acid bacteria and yeasts in a hamster model of Clostridium difficile infection.
Anaerobe 21, 28— Botelho, P. Characterization of a new exopolysaccharide obtained from of fermented kefir grains in soymilk. Carasi, P. Surface proteins from Lactobacillus kefir antagonize in vitro cytotoxic effect of Clostridium difficile toxins. Anaerobe 18, — Cevikbas, A. Antitumoural, antibacterial and antifungal activities of kefir and kefir grain.
Cheirsilp, B. Use of whey lactose from dairy industry for economical kefiran production by Lactobacillus kefiranofaciens in mixed cultures with yeasts. Enhanced kefiran production by mixed culture of Lactobacillus kefiranofaciens and Saccharomyces cerevisiae. Chen, H. Microbiological study of lactic acid bacteria in kefir grains by culture-dependent and culture-independent methods. Chen, Y. Lactobacillus kefiranofaciens M1 isolated from milk kefir grains ameliorates experimental colitis in vitro and in vivo.
Dairy Sci. Chen, Z. Chemical and physical characteristics and antioxidant activities of the exopolysaccharide produced by Tibetan kefir grains during milk fermentation.
Dairy J. De Vuyst, L. Heteropolysaccharides from lactic acid bacteria. FEMS Microbiol. Recent developments in the biosynthesis and applications of heteropolysaccharides from lactic acid bacteria.
Diniz, R. JavaScript seems to be disabled in your browser. You must have JavaScript enabled in your browser to utilize the functionality of this website. The latter contains a proprietary blend of various bacteria strains, the former is a bit more complex.
Milk kefir grains are a mother culture made up of polysaccharides, the primary of which is kefiran[1]. Within this matrix of polysaccharides exists both bacteria and yeasts which exist in symbiosis both with each other and the milk it cultures and feeds from.
These grains have a gelatinous feel to them and appear in a sort of miniature floret shape, much like cauliflower. The bacteria and yeast composition of milk kefir grains tend to vary according to their origin as well as their culturing environment.
In other words, where the grains came from and where they are currently being used can impact the makeup of the microorganisms existing in the milk kefir grains. Milk Kefir Starter Kit. Milk Kefir Grains. Water Kefir Starter Kit. Water Kefir Grains. This is a common question and one worth delving into. Most sources agree that the milk kefir grain culture was harnessed somewhere near the Caucasus Mountains. The grains themselves are quite unusual in that no other cultured dairy product is known to come from grains.
Though the specifics of the origination of milk kefir grains are fairly shrouded in mystery, one thing has been made clear: milk kefir grains must be acquired. The specific polysaccharides, bacteria, and yeasts that makeup milk kefir grains have been handed down from generation to generation. Kefir's History.
Kefir dates back many centuries to the shepherds of the Caucasus mountains. They discovered that fresh milk carried in leather pouches would occasionally ferment into an effervescent beverage.
In the Caucasian Mountains, legend has it that the resulting kefir "grains not really a true grain were a gift to Orthodox people from Mohammed, who instructed them on how to use the grains. Mohammed strictly forbade them from giving away the secret of kefir preparation to other people, or pass anyone kefir grains, because they would lose their "magic strength. For most of recorded history, kefir was scarcely known outside the Caucasian Mountains, although Marco Polo mentioned it in recounting his travels.
This self-carbonated dairy-based beverage continues to be popular in Russia, southwestern Asia and Eastern and Northern Europe, and has recently gained some popularity in the United States.
Kefir's Production. Basically, kefir is made by fermentation of the "kefir" grains, which resembles miniature cauliflowers that are the size of wheat kernels. These grains consist of casein and gelatinous colonies of microorganisms that are grown together symbiotically. The dominant microflora are Saccharomyces kefir, Torula kefir, Lactobacillus caucasicus, Leuconnostoc species and lactic streptococci. In addition, some yeast is present.
These many beneficial microorganisms are what separates kefir from virtually all other cultured milk products, which typically use only one, and rarely more than three species in the culturing process. These microorganisms produce a variety of changes in the milk. Kefir's Health Benefits. The cultures' chemical changes make the milk much easier to digest, allowing the body to absorb more of the naturally present nutrients.
The transformation of lactose to lactic acid allows people, even t hose with lactose intolerance, to digest kefir and get its full benefits. Kefir is high in calcium, amino acids, B-vitamins and folic acid. Kefir can play a vital role in the development of a healthy digestive tract in babies, as it protects against negative effects of radiation and helps improve the immune system. Kefir's friendly cultures also produce specific antibiotic substances which can control undesirable microorganisms and act as anti-carcinogenic factors.
Kefir also helps to enhance bowel function and control candida - a condition where there is an excessive growth of yeast cells. In reference to Candida, Dr. Orla-Jenson, a noted Danish bacteriologist specializing in dairy research states that "Kefir digests yeast cells and has a beneficial effect on the intestinal flora". An international Nobel prize winning researcher, Elie Metchnikoff found that kefir activates the flow of saliva, most likely due to its lactic acid content and its slight amount of carbonation.
Kefir stimulates peristalsis and digestive juices in the intestinal tract. For these reasons it is recommended as a postoperative food since most abdominal operations cause the bowels to stop contracting and pushing food along peristalsis.
Kefir's unique properties include its use as a remedy for digestive troubles because of its very low curd tension, meaning that the curd breaks up very easily into extremely small particles. The curd of yogurt, on the other hand, holds together or breaks up into lumps. The small size of the kefir curd facilitates digestion by presenting a large surface for digestion agents to work on.
In addition, kefir possesses mild laxative properties. It is also recommended to restore the intestinal flora of people who are recovering from a serious illness or being treated with antibiotics. Kefir is predigested due to the fermentation process rendering itself tolerable to those persons who can not tolerate dairy products. The story of kefir is littered with distinction: a 2, year history, a mention by Marco Polo, and, in the s, a symbolic gift exchanged between superpowers at the end of the cold war.
Kefir is a fermented milk product containing live probiotic organisms and rich in nutrients required by the body: proteins, minerals and vitamins. It is produced by adding a fermented grain culture to milk. Produced in ancient times by nomadic shepherds in the Balkans, kefir was little known in the West for 1, years, despite being mentioned by Marco Polo. Then, by order of the Russian Czar, it was brought to Russia at the beginning of the twentieth century and became popular in many parts of Europe.
K efir is a cultured, creamy product with amazing health attributes. Its tart and refreshing flavor is similar to a drinking-style yogurt, but it contains beneficial yeast as well as friendly 'probiotic' bacteria found in yogurt. The naturally occurring bacteria and yeast in kefir combine symbiotically to give superior health benefits when consumed regularly.
It is loaded with valuable vitamins and minerals, it contains easily digestible complete proteins, and it boasts natural antibiotic properties - a natural antibiotic made with milk! For the lactose intolerant, kefir's abundance of beneficial yeast and bacteria provide lactase, an enzyme which consumes most of the lactose left after the culturing process. Kefir can be made from any type of milk, cow, goat or sheep, coconut, rice or soy.
Although it is slightly mucous forming, the mucous has a "clean" quality to it that creates ideal conditions in the digestive tract for the colonization of friendly bacteria.
Kefir is made from gelatinous white or yellow particles called "grains. They look like pieces of coral or small clumps of cauliflower and range from the size of a grain of wheat to that of a hazelnut.
Some of the grains have been known to grow in large flat sheets that can be big enough to cover your hand!. The grains ferment the milk, incorporating their friendly organisms to create the cultured product.
The grains are then removed with a strainer before consumption of the kefir and added to a new batch of milk. I n addition to beneficial bacteria and yeast, kefir contains minerals and essential amino acids that help the body with healing and maintenance functions. The complete proteins in kefir are partially digested and therefore more easily utilized by the body.
Tryptophan, one of the essential amino acids abundant in kefir, is well known for its relaxing effect on the nervous system. Because kefir also offers an abundance of calcium and magnesium, which are also important minerals for a healthy nervous system, kefir in the diet can have a particularly profound calming effect on the nerves.
Kefir's ample supply of phosphorus, the second most abundant mineral in our bodies, helps utilize carbohydrates, fats, and proteins for cell growth, maintenance and energy. It is an excellent source of biotin, a B Vitamin which aids the body's assimilation of other B Vitamins, such as folic acid, pantothenic acid, and B The numerous benefits of maintaining adequate B vitamin intake range from regulation of the kidneys, liver and nervous system to helping relieve skin disorders, boost energy and promote longevity.
T he benefits of consuming kefir regularly in the diet are numerous. Easily digested, it cleanses the intestines, provides beneficial bacteria and yeast, vitamins and minerals, and complete proteins. Because kefir is such a balanced and nourishing food, it contributes to a healthy immune system and has been used to help patients suffering from AIDS , chronic fatigue syndrome, herpes, and cancer.
Its tranquilizing effect on the nervous system has benefited many who suffer from sleep disorders, depression, and ADHD attention deficit hyperactivity disorder. The regular use of kefir can help relieve all intestinal disorders, promote bowel movement, reduce flatulence and create a healthier digestive system.
In addition, its cleansing effect on the whole body helps to establish a balanced inner ecosystem for optimum health and longevity. Kefir can also help eliminate unhealthy food cravings by making the body more nourished and balanced. Its excellent nutritional content offers healing and health-maintenance benefits to people in every type of condition. Two delicious kefir recipes. Make kefir with the freshest milk possible and add as many of the following ingredients as desired:.
Blend together for a delicious, nutritious breakfast, lunch, or snack and enjoy! Cool Kefir Dressing No Oil. Combine all ingredients except xanthan gum and blend thoroughly. Slowly add xanthan gum and continue to blend until mixture thickens. Full flavor will develop after 6 to 8 hours. Note: Dairy products combine best with nonstarchy vegetables and acid fruits. Don't hesitate to add a little Flax Seed Oil to this recipe.
T he easiest way to have fresh kefir available any time is to make it yourself! Among the benefits of homemade kefir: you can choose the milk you use -- organic, nonfat, low fat, whole, goat's or cow's milk; it's very rich in microorganisms, and, of course, it can't get any fresher. These are divided into four Genus groups:. Kluyveromyces lactis Kluyveromyces marxianus var.
Torulopsis holmii. Acetobacters aceti A. International Journal of Systematic Bacteriology 44 3 [21 ref. Research shows that units count of microbes in kefir grains that were Gram stained were: Bacilli single cells, pair, chains , Streptococci pair, chains and Yeast single cells.
Note: I have no knowledge of C. These two wonderful articles were written by Cathy J. Saloff-Coste from Danone at their website www. Abstract Kefir is a refreshing fermented milk with a slightly acidic taste. It is made only from kefir grains or mother cultures prepared from grains, although attempts to produce kefir with pure cultures are in progress.
Kefir grains are a complex and specific mixture of bacteria and yeasts held together by a polysaccharide matrix. The lactic acid bacteria and yeast fermentation of milk results in the production of numerous components, including lactic acid, CO2, a small amount of alcohol, and an array of aromatic molecules, all of which provide kefir with its unique organoleptic properties.
Many health benefits related to the consumption of kefir have been observed, but rigorous research using modern scientific methods is in its early stages. Introduction Kefir is a fermented drink which has been consumed for thousands of years.
It originated in the Caucasus mountains in the former Soviet Union where the drink was fermented naturally in bags made of animal hides. Its use is currently being expanded because of its unique organoleptic properties and its long tradition of health benefits. Kefir distinguishes itself from the more known fermented milk yogurt in that it is traditionally made only from kefir grains which contain a complex mixture of both bacteria and yeasts.
The resulting kefir possesses unique organoleptic characteristics. Research on its health benefits is just beginning, and there remain many questions unanswered. Two types of kefir exist: sugary, a fermented sweetened water; and milky, a fermented milk beverage. This article addresses the milky variety, whose norm has been established by the International Dairy Federation 2 , and it will provide an overview of its characteristics and a discussion of its potential health benefits.
Characteristics and consumption of kefir Kefir is a refreshing slightly carbonated and acidic fermented milk 3. It can be consumed as is, or can be used in cooking in soups, sauces, and cakes.
The distinctive organoleptic properties differ from yogurt in that small amounts of CO2, alcohol, and aromatic molecules are produced as a result of a dual fermentation of lactic acid bacteria and yeasts. Although kefir is just being discovered in some areas of the world, it has been very popular in the former Soviet Union, Hungary, and Poland for many years.
It is currently available in the United States, primarily as an ethnic drink, and is growing in popularity in Japan. Kefir grains While yogurt can readily be made from the lactic acid bacteria present in fresh yogurt, kefir can only be made from kefir grains and mother cultures prepared from grains.
The grains contain a relatively stable and specific balance of microorganisms which exist in a complex symbiotic relationship. The grains are formed in the process of making kefir and only from pre-existing grains.
They resemble small cauliflower florets, and each grain is 3 to 20 mm in diameter 7. Kefir grains are clusters of microorganisms held together by a matrix of polysaccharides.
The grains include primarily lactic acid bacteria lactobacilli, lactococci, leuconostocs and yeasts, and include acetic acid bacteria and possibly other microorganisms 8. The overall organization of microorganisms of grains is not completely elucidated. More than a thousand years of consumption have demonstrated that the microorganisms in kefir are not pathogenic. Even further, milk inoculated with grains can suppress the growth of some pathogens such as Salmonella or Shigella 1.
The principal polysaccharide is a water-soluble substance known as kefiran. Several homofermentative Lactobacillus species including L. They are an integral part of the grain, and without their presence, kefir grains cannot be propagated.
The mechanism, however, is not fully understood. Fabrication of kefir There exist several methods of producing kefir see Figure 1. Food scientists are currently studying modern techniques to produce a kefir with the same characteristics as those found in traditional kefir, but without some of its drawbacks. After a period of fermentation lasting around 24 hours, the grains are removed by filtration.
The beverage, itself containing live microflora from the grain see Table 1 , is then ready for consumption. The grains grow in the process of kefir production, and are reused for subsequent fermentations 6. For a longer conservation, they can be lyophilized freeze-dried or frozen A second method, known as the"Russian method", permits production of kefir on a larger scale, and uses a series of two fermentations.
Several problems associated with traditional kefir have led to a more modern method of production. The traditional method produces only small volumes of kefir, and requires several steps, each additional step increasing the risk of contamination. In addition, the grains themselves are not well understood, and are not well controlled.
Strong pressure from the CO2 gas content can lead to the explosion of the recipient unless appropriate containers which resist the escaping of gas are used Finally, the shelf-life of traditional kefir is very short, less than three days.
Recent process To resolve the above difficulties, some producers in Eastern Europe have begun using concentrated lyophilized cultures made from grains 7. These mother cultures are then used as bulk starters for direct inoculation of the milk.
More control over the process and fewer steps provide a more consistent quality. Current areas of research Attention is now being turned toward producing kefir from pure, defined cultures This method will allow for a better control of the microorganisms involved, an ease of production, and a more consistent quality. It will also permit various modifications of the product to achieve certain health or nutritional benefits.
Two basic procedures for manufacturing kefir have been developed using pure cultures isolated from kefir grains. Milk can be inoculated simultaneously with lactic acid bacteria and yeast, or it can undergo two fermentations, the first with lactic acid bacteria and the second with yeast. Results have been encouraging, but finding the right equilibrium of bacterial and yeast strains to create a product with the characteristic properties of traditional kefir including both the organoleptic qualities and the health benefits - is a difficult task.
The major difficulty is understanding the microbiology of kefir. The microbiological, chemical, and nutritional composition of kefir The composition and flavor of kefir vary significantly, depending on a variety of factors including the source cow, ewe, goat, mare 18 and the fat content regular fat, lowfat, nonfat of the milk used, the composition of the grains or starters, and the technological conditions of production Table 2 lists some of the biochemical components of the range of kefir.
The major products formed during fermentation are lactic acid, CO2, and alcohol. Many aromatic compounds, including diacetyl and acetaldehyde are present in kefir Diacetyl is produced by Str. The pH of kefir is 4. As in yogurt, the lactose content is reduced in kefir 14 , and the b-galactosidase level is increased as a result of fermentation.
Information on vitamin and mineral content is limited and sometimes contradictory, but overall, there do not seem to be significant variations from that of the milk used. There is also a small increase in proteolysis, leading to an increase in free amino acids 2. Health properties of kefir Kefir enjoys a rich tradition of health claims. In the former Soviet Union, it is used in hospitals and sanatoria for a variety of conditions, including metabolic disorders, atherosclerosis, and allergic disease 1.
It has even been used for the treatment of tuberculosis, cancer, and gastrointestinal disorders when no modern medical treatment was available. Its consumption has also been associated with longevity in Caucasus Various scientists have observed digestive benefits of kefir 21, 22 , but controlled studies have yet to confirm their empirical findings. Various research teams around the world have reported encouraging results, but several methodological difficulties still need to be resolved.
Most studies to date have been performed in vitro or using animal models, and human studies are not available. Further, the effects of kefir grains or their isolates are often studied, rather than the product kefir, and there is no evidence that the observed effects would occur using the drink itself. Also, kefir products vary significantly according to the composition of the grains used and even according to the region in which it is made, and therefore specific effects may not be demonstrated in all kefirs.
Given these caveat, a variety of health benefits are being investigated. Table 3 presents recent studies using kefir products. Several studies have investigated the antitumor activity of kefir 20, 23, 24 and of kefir grains 25, Specific cultures isolated from kefir were also shown to bind to mutagenic substances such as indole and imidazole 27, Immune system stimulation with kefir 24 and with sphingomyelin isolated from the lipids of kefir 29 have been demonstrated in both in vitro and in vivo studies.
Kefir 30 possesses antimicrobial activity in vitro against a wide variety of gram-positive and gram-negative bacteria 20, 31 , and against some fungi In Zacconi et al. De Vrese et al. This effect was attributed to microbial b-galactosidase activity of kefir. The above studies provide encouraging results, but much more research is necessary in order to demonstrate similar effects using kefir in humans.
Further, a standardized, well-defined product must be used in order to provide useful information. Abstract Research on fermented milks FM has grown dramatically in the past 20 years. FM have probiotic effects since their consumption leads to the ingestion of large numbers of live bacteria which exert health benefits beyond basic nutrition. Major results of research are as follows. Yogurt consumption reduces symptoms of lactose maldigestion compared to milk.
FM, may have antibacterial and immunological properties. Ingestion of the lactic acid bacteria bifidobacteria improves the colonic microflora by increasing bifidobacteria levels. Lactobacillus casei reduces the duration of some types of diarrhea.
Future research conducted using human subjects, with rigorous methodology and modern statistical analysis, will provide further information on the health benefits of FM. Keywords: fermented milk, probiotic, yogurt, kefir, Lactobacillus streptococcus, Streptococcus thermophilus, Lactobacillus casei, bifidobacterium.
Glossary Lactic acid bacteria LAB : a large group of bacteria with the common characteristic of producing lactic acid as the principal end product of metabolism; found in milk and other natural environments LAB can be: a.
Facultatively prefer anaerobic anaerobic: conditions for metabolism, but are aero-tolerant most LAB fit in this b. Strictly anaerobic: survive only in anaerobic conditions; e. Interleukin, interferon, tumor necrosis factor: examples of cytokines, which serve as signals between cells involved in immune response.
From legend to science: Historical perspective For centuries, fermented milks have been purported to provide a large gamut of health benefits, from improving well-being to increasing longevity. He brought with him sheep and a secret recipe for yogurt. The king was soon cured of his intestinal infection. Scientific interest began much later, in the early twentieth century, when Elie Metchnikoff, a Nobel-prize winning biologist at the Pasteur Institute in Paris, first suggested that lactobacilli might counteract the putrefactive effects of gastrointestinal metabolism 1.
In the past twenty years, scientific research has blossomed, with an interest in topics ranging from antimicrobial effects to reduction of risk of cancer. Much valuable preliminary work has been done using animal or in vitro models, which allow for much greater control over variables than when studying humans, and which offer reproducible results.
These models are also useful for studying the mechanisms involved. Studying the effects of FM on humans presents several challenges. Fermented milksare unctional foods, and as such, their impact on human physiology is of a small amplitude and not easily detected. Also, early humans studies, though numerous, were generally case reports rather than modern experimental studies randomized. Currently, researchers are beginning to address these methodological problems.
0コメント