Kefir and Koumiss Origin, Health Benefits and Current Status of Knowledge

Full text

Food Biology Series
Fermented Foods
Part II: Technological Intervention
Editors
Ramesh C. Ray
Principal Scientist (Microbiology)
ICAR
- Central Tuber Crops Research Institute
Bhubaneswar, Odisha, India
and
Didier Montet
Food
Safety Team Leader UMR
Qualisud, CIRAD Montpellier,
France
A SCIENCE PUBLISHERS BOOK

18
Ker and Koumiss
Origin, Health Benets and Current
Status of Knowledge
Sunil K. Behera,1,* Sandeep K. Panda,2 Eugenie Kayitesi 2 and
Antoine F. Mulaba-Bafubiandi1
1. Introduction
Milk constitutes an important ingredient of healthy balanced diet of our
daily life. It is an important source of vitamins, minerals, and proteins
for human nutritional requirement, hence regarded as a complete food.
Throughout the world, milk and milk products are valued as natural and
traditional food. However, milk is extremely perishable and many means
have been adapted to preserve it. The earliest one which has been used
for many thousands of years is the process of fermentation (Parveen and
Hafiz 2003). Milk can be fermented by inoculating fresh milk with the
appropriate bacteria and incubating it at a temperature that favors their
growth. As the bacteria grow, they convert milk sugar (lactose) to lactic
acid through the process of fermentation. The lactic acid generated during
milk fermentation decreases the pH of milk and as a result it prevents the
growth of putrefactive and/or pathogenic microorganisms that do not
survive in acidic environment. Since the time immemorial the process of
1 Department of Metallurgy, Faculty of Engineering and the Built Environment, University
of Johannesburg, P.O. Box 17911, Doornfontein Campus, 2028, Johannesburg, South Africa.
2 Department of Biotechnology and Food Technology, Faculty of Science, University of
Johannesburg, Doornfontein Campus, Johannesburg, South Africa, P.O. Box 17011.
* Corresponding author: skbehera2020@gmail.com
Fermented Food—Part II: Technological Interventions Not for Circulation
Ramesh C. Ray and Didier Montet (eds.)
ISBN 978-1-1386-3784-9

Kefir and Koumiss: Origin, Health Benefits and Current Status of Knowledge
401
fermentation has been adapted as a tool for food preservation. With due
course of time, it has been noticed that many fermented foods have better
nutritional and functional values when compared to their unfermented
counterparts (Hasan et al. 2014). Hence the fermentation processes have
become the most popular food processing techniques for preservation of
foods along and for the addition of better nutritional value (Panda et al.
2014a, 2014b). Worldwide, the known fermented milk products are yogurt,
kefir, koumiss, sour cream, cheeses, etc.
The primary function of fermenting milk was, originally, to extend its
shelf life. Further the fermentation process brought numerous changes to
the nutritional property of milk, such as an improved taste and flavor and
enhanced digestibility of the milk. Historically, the fermentation of milk
can be traced back to around 10,000 B.C. (Dhewa et al. 2015). Fermentation
takes place through the natural microflora present in milk. With the advent
of scientific methods the different classes of microorganisms present in the
fermented dairy products have been detected.
The most common microorganisms observed in fermented milk products
belong to the strains of lactic acid bacteria (LAB), Lactobacillus, Leuconostoc,
Lactococcus, etc. (Liu et al. 2014). These microorganisms prevent the spoilage
of milk and inhibit the growth of other pathogenic microorganisms. Today
the fermentation processes are controlled with specific starter cultures and
conditions to obtain a wide range of milk products like milk cream, cultured
buttermilk, kefir, koumiss, yogurt and amasi. Different starter cultures are
used for each fermented dairy product. They consist of microorganisms
added to the milk to provide specific characteristics in the final fermented
milk product with desired properties. The vital function of lactic acid
starters is for fermentation of lactose into lactic acid. In addition, they
also contribute to flavor, aroma and alcohol production, while inhibiting
interference of spoilage microorganisms. A single strain of bacteria may be
added, or a mixture of several microorganisms may be introduced. Bacteria,
yeasts and molds perform the process of fermentation at specific range
of optimum temperatures. The optimum temperature for thermophilic
lactic acid fermentation is about 40 to 45°C, while mesophilic lactic acid
fermentation occurs at moderate temperatures ranging from 30 to 40°C
(Carminati et al. 2010).
Microbial fermentation is the biochemical conversion of carbohydrates
into alcohols or acids (Panda et al. 2013, Panda et al. 2016). In fermented
milk products both alcohol and lactic acid may be produced, e.g., kefir
and koumiss, or only lactic acid, e.g., sour milk cream. The bacteria
convert the lactose to lactic acid and raise the acidity of the milk. The rise
in acidity causes denature of milk proteins thus inhibiting the growth of
other organisms that are not acid tolerant. Following the completion of
fermentation process, the fermented dairy products are marketed with
added flavors.

402 Fermented Foods—Part II: Technological Interventions
In addition to extending the shelf life of milk products, the fermentation
process gives probiotic properties to the milk products (Amara and Shibl
2015). After invention of the microscope, the microbiological studies revealed
that the fermented milk products contain live microorganisms and the
microbial metabolites that are highly beneficial for human health (Fernandez
et al. 2015). Further development of scientific knowledge has made it clear
that the human intestinal microflora consists of trillions of microbial cells.
These microorganisms play a vital role in several physiological activities,
metabolic activities and immune functions (Guinane and Cotter 2013).
Historically the fermented milk products have health benefits and have
a good taste which enables their consumption, hence milk was the first
probiotics food adapted by the men (Amara and Shibl 2015). Men knew
how to prepare different types of fermented milk products even before the
invention of the microscope (Amara and Shibl 2015). The different types of
the microorganisms used as starter culture induce different reactions and as
a result it produces different types of fermented products like yogurt, kefir,
koumiss, sour cream, etc. The knowledge of such traditional processes for
food preservation is transferred from generation to generation. Looking to
the importance of the beneficial properties of kefir and koumiss, this chapter
describes the nutritional importance and health promoting properties of
kefir and koumiss.
2. Ker
Kefir is a fermented milk drink which is traditionally produced by
fermenting cow, goat and sheep milk by using “kefir grains” as starter
culture (Farnworth 2005). The kefir grains contain active microorganisms
and when added to fresh milk, they produce kefir. Kefir grains consist of
protein and polysaccharide matrix containing different species of yeasts,
LAB, acetic acid bacteria, and mycelial fungi (Witthuhn et al. 2005). Kefir
produced through the fermentation of milk by the microorganisms is a white
or yellowish colored, sour, carbonated and a mild alcoholic beverage. It
has yeasty aroma with acidic taste (Irigoyen et al. 2005). Kefir is sometimes
commercially available without carbonation and alcohol (when yeast is not
added to the starter culture), resulting in a product that is very similar to
yogurt. The flavor, taste, nutritional composition of kefir varies with the
type of milk and microbial strains used for kefir production.
Kefir originated from the Caucasian mountains and then it became
popular in central and Eastern Europe (Assadi et al. 2000). It is important
food stuff in Russia. Traditionally kefir is produced in the households of
the Caucasian Mountains and Tibetian region of China. They used the kefir
grains which were inherited from their ancestors for kefir preparation.

Kefir and Koumiss: Origin, Health Benefits and Current Status of Knowledge
403
Generally, kefir is prepared from cow, sheep and goat milk; however soya
milk is also known to be used for kefir preparation (Farnworth 2005).
In the later part of the nineteenth century, the benefit of kefir was
highlighted when it helped for effective treatment of tuberculosis, intestinal
and chronic diseases in the Caucasus region. The benefits of kefir were first
reported by the Russian doctors working in this region. Kefir has been
reported for its healing effects on the high blood pressure, anaemia, obesity
control, gall bladder problem, etc. (Bellamy and MacLean 2005). Due to its
abundant health benefits, kefir has gained popularity as a functional healthy
probiotic food throughout the world.
2.1 Ker production
Kefir production started from the indigenous process by incubating the
kefir grains with milk of cow, sheep or goat. Later the process was refined
scientifically to produce it on a commercial scale.
2.1.1 Ker grains
Microorganisms present in kefir grains are responsible for the fermentation
of milk. The original kefir grains are slightly yellowish in colour and they
resemble a cauliflower (Nielsen et al. 2014). There is no scientific evidence
about the origin of kefir grains. Kefir grains are yellowish-white, cauliflower
shaped, semi hard granules containing different yeast and bacterial stains,
which exist in symbiotic association (Fig. 1). When the grains are added
to sterilized milk and incubated the microorganisms are activated to
ferment milk. Kefir grains are made up of a complex microbial biomass
matrix composed of polysaccharide, fat and protein of kefir microorganism
Figure 1. Kefir grain.
(source: https://julietwhev.files.wordpress.com/2013/03/kefir-grains.jpg).

404 Fermented Foods—Part II: Technological Interventions
origin (Rea et al. 1996). Microorganisms involved in kefir production
secrete exopolysaccharides that accumulate along with proteins and fat
molecules to form kefir grains. Further, growth of kefir grains occur by the
accumulation of microbial biomass on the pre-existing kefir grains during
kefir production. The major constituent of kefir grain matrix is composed
of polysaccharide “kefiran” (La Riviere et al. 1967). The kefiran is a hetero-
polysaccharide made from glucose and galactose. Lactic acid bacteria are
the main exopolysaccharide producing microorganisms in kefir that give the
rheological and texture properties to the kefir formed from the fermented
milk (Frengova et al. 2002).
2.1.2 Traditional/Indigenous process of ker production
The traditional process for kefir preparation is described as follows:
(a) Incubation of milk (cow, sheep or goat) with kefir grains at room
temperature for 24 hr; (b) At the end of the incubation period kefir grains
are separated from milk by filtration process; (c) the fermented milk, i.e.,
the kefir is preserved for further consumption. The kefir grains separated
from the kefir can be further reused as a starter culture for preparation of
kefir from fresh batch of milk.
2.1.3 Modern process of ker production
The kefir can be prepared from the milk of sheep, cow or goat. For large
scale production of kefir, kefir grains are not used but rather sterilized
milk is incubated with selected microorganisms directly. At the industrial
scale, at first the milk is sterilized by the process of homogenization and
pasteurization. After sterilization the milk is kept for cooling down up to
20°C and the milk is incubated with specific strains of microorganisms for
24 hr further to prepare kefir (Assadi et al. 2000, Otles and Cagindi 2003).
The nutritional and sensory qualities of kefir vary with the type of milk and
microbial strain used. The taste, flavor and aroma of kefir differ from other
milk products because it is a produced through a combination of eukaryotic
and prokaryotic (yeast and bacteria) fermentation process. A typical process
of kefir production is graphically presented in Fig. 2.
Kefir resembles yogurt to some extent. Many people believe that kefir
and yogurt are similar, but in reality they have many significant differences
based on biochemical and organoleptic properties. Both kefir and yogurt are
cultured milk products but they contain different strains of microorganisms.
Generally, yogurt contains bacterial strains that belong to the genera of
Lactobacillus and Streptococcus, while kefir contains several other bacterial

Kefir and Koumiss: Origin, Health Benefits and Current Status of Knowledge
405
strains such as Lactobacillus, Leuconostoc, Acetobacter, Streptococcus and
Pseudomonas spp. Apart from the bacterial strains, kefir contains different
yeast strains belonging to Saccharomyces, Candida and Kluyveromyces genus,
hence kefir is a fermented milk product of combined action of yeast and
bacterial fermentation process. Appearance of kefir is not as creamy as
yogurt. Generally, kefir has a sourer or tart taste due to lactic acid content.
It has a little effervescence, due to the carbon dioxide and alcohol content
released by alcoholic fermentation. The acidity generated drops the pH
of milk up to 4 to 4.5, and it varies depending on the type of milk and
fermentation conditions.
3. Koumiss
Koumiss is a traditional milk beverage produced from fermentation of
mares’ milk by indigenous microorganisms (Montanari et al. 1996). Koumiss
is also known by other names like koumiss, kumiss, kumis, kymis, kymmyz. It
is a fermented drink traditionally made from the milk of horses by people
in Central Asia and China, where it is one of the most important basic
foodstuffs. Koumiss is similar to the kefir; however it is prepared by a liquid
starter culture in contrast to the solid kefir grains used in kefir production.
Koumiss is also widely produced in Russia, Kazakhstan in Western Asia. In
Mongolia, it has been adapted as the national drink and is known as Airag
(Uniacke-Lowe et al. 2010).
Figure 2. A typical process of Kefir production.

406 Fermented Foods—Part II: Technological Interventions
3.1 Preparation of Koumiss
In the traditional process, koumiss is prepared by incubating fresh mare’s
milk with a part of the previous day’s batch of koumiss as a starter
culture. The previous day’s batch of koumiss containing indigenous native
microorganisms is inoculated to fresh mares’ milk and kept for about 8 hr
of incubation (Cagno et al. 2004). The milk is fermented by the LAB and
yeast to produce lacto-alcoholic rich beverage. The preparation of koumiss
is presented in Fig. 3.
Unlike kefir, which is prepared from the milk of cow, sheep or goat, the
mare and camel milk used for koumiss production gives the product its
distinctive character. The higher lactic acid and alcoholic content observed
in koumiss in comparison to kefir is attributed to the higher sugar content of
mare’s milk used in koumiss preparation (Uniacke-Lowe et al. 2010, Bornaz
et al. 2010). The average chemical composition of mare’s milk and bovine
milk shows that the mare’s milk has a distinct composition. The noticeable
differences between these milks shows that the mares milk contain lower
fat (12.1 g/kg) and higher lactose (63.7 g/kg) content compared to bovine
milk (Uniacke-Lowe et al. 2010). The predominant microbial strains used
for koumiss are LAB and yeast strains of Saccharomyces (Wouters et al.
2002). The lactic acid produced by the lactic acid bacterial strains gives the
koumiss an acidic characteristic and the yeasts generate alcohol in koumiss
through alcoholic fermentation process. Thus the koumiss obtained by the
fermentation of mare’s milk is a milky grey, fizzy liquid with a sharp alcohol
and acidic taste. Since the mare’s milk has higher lactose content, the final
fermented product, i.e., koumiss has comparatively higher lactic acid and
Figure 3. A typical process of Koumiss production.
28

Figure 3. A typical process of Koumiss production

Kefir and Koumiss: Origin, Health Benefits and Current Status of Knowledge
407
alcoholic content when compared with kefir. Koumiss contains alcohol up
to 2%, and therefore, it is also called milk wine. Although the koumiss is
a popular fermented milk beverage, the availability of the mare’s milk is
the limiting factor for its large scale production. Presently, the large scale
production of koumiss is performed from cow’s milk supplemented with
the additional sugar to make it approximate with the composition of mare’s
milk (Zhang and Zhang 2012).
4. Microorganisms Associated With Ker and Koumiss
The microbial diversity of kefir and koumiss is very complex. However,
several reports have described the microbial diversity with these two
products. The microorganisms entrapped in the protein and polysaccharide
matrix of the kefir grains live symbiotically (Lopitz-Otsoa et al. 2006). The
microbial populations presented in the grains mostly belong to LAB, acetic
acid bacteria (AAB), yeasts, and mycelia fungi (Marshall 1984, Witthuhn
et al. 2005). A brief list of microorganisms detected in different kefirs is
described in the Table 1.
The notable bacterial strains found in kefir are Lactobacillus acidophilus,
Lb. brevis, Lb. casei, Lb. fermentum, Lb. helveticus, Lb. kefir, Lb. parakefiri,
Lactococcus lactis, Leuconostoc mesenteroides, Lb. delbrueckii, Acetobacter sicerae
sp. nov, Streptococcus, etc. (Witthuhn et al. 2005, Simova et al. 2002, Li et
al. 2014).
Several strains of yeasts have also been reported in kefir such as
Kluyveromyces marxianus, Torula kefir, Saccharomyces exiguus, Candida lambica,
Candida kefir, Saccharomyces cerevisiae, Candida krusei and Candida famata
(Lopitz-Otsoa et al. 2006, Witthuhn et al. 2005). Yeast cells provide flavor
and aroma to kefir (Simova et al. 2002). In addition, they provide essential
nutrients (vitamins and amino acids) for bacteria growth and thus assist
growth of bacterial strains present in kefir (Farnworth 2005, Irigoyen et
al. 2005). Furthermore, they inhibit growth of pathogenic microorganisms
by decreasing the pH of the medium through the production of ethanol,
carbon dioxide and organic acids.
The notable microorganisms present in the starter culture used for
koumiss preparation belong to the bacterial strains of Lactobacillus and
Lactococcus, and fungal strains of Kluyveromyces and Saccharomyces (Uniacke-
Lowe et al. 2010). Cagno et al. (2004) reported the use of bacterial strains
Lactobacillus delbrueckii and Streptococcus thermophillus in starter culture for
the preparation of koumiss from mare’s milk. Brief lists of microorganisms
detected in different koumiss are described in the Table 2.

408 Fermented Foods—Part II: Technological Interventions
Table 1. Microorganisms associated with Kefir.
Microorganisms References
Lactococcus spp.,
Lactobacillus spp.
Cui et al. 2013,
Chen et al. 2008,
Simova et al. 2002
Lactobacillus keranofaciens Chen et al. 2008
Lactobacillus buchneri Garofalo et al. 2015
Lactobacillus plantarum Wang et al. 2015
Lactobacillus kefiri Chen et al. 2008
Acetobacter aceti Li et al. 2014
Kluyveromyces marxianus Wang et al. 2012
Chang et al. 2014
Saccharomyces turicensis Wang et al. 2012
Pichia fermentans Wang et al. 2012
Kazachstaniaunispora Garofalo et al. 2015
Dekkeraanomala Garofalo et al. 2015
Yeast Soupioni et al. 2013
Table 2. Microorganisms associated with Koumiss.
Microorganisms References
Lactobacillus spp. Guo et al. 2015
Lb. acidophilus El-Ghaish et al. 2011
Lb. helveticus Miyamoto et al. 2015
Lb. salivarius Danova et al. 2005
Lb. buchneri Danova et al. 2005
Lb. plantarum Danova et al. 2005
Lb. delbrueckii Cagno et al. 2004
Streptococcus spp. Kozhahmetova et al. 2013
Str. thermophiles Cagno et al. 2004
Leuconostoc Guzel-Seydim et al. 2009
Yeasts El-Ghaish et al. 2011
Torula kumiss Kosikowski 1982
Saccharomyces lactis Kosikowski 1982
Saccharomyces unisporus Montanari et al. 1996
Kluyveromyces lactis Kucukcetin et al. 2003
5. Biochemical Mechanisms Involved in The Production of
Ker and Koumiss
The biochemistry of kefir and koumiss production depends upon the type
of lactic acid fermentation occurred, namely homo fermentation and hetero
fermentation. The homo fermentative microorganisms produce only lactic

Kefir and Koumiss: Origin, Health Benefits and Current Status of Knowledge
409
acid as the final product whereas the hetero fermentative microorganisms
produce ethanol and CO2 along with lactic acid. The details of the homo
and hetero lacto-fermentation have been described in the previous chapter
of this book (see Chapter 17).
The characteristic flavor of kefir and koumiss are due to the presence
of various biochemical compounds formed during fermentation process,
such as organic acids (lactic, propionic, citric, acetic, pyruvic and succinic
acids, etc.). These acids are produced due to the metabolism of milk by the
microorganisms involved in milk fermentation (Guzel-Seydim et al. 2000).
The microorganisms present in kefir, metabolise the milk sugar to
produce energy through the biochemical process of glycolysis and other
metabolic pathways (alcoholic and lactic acid fermentation and Krebs cycle).
The final product formed in glycolysis is pyruvic acid. Further, metabolic
process depends on the availability of the oxygen for the microorganisms
present in kefir. In presence of oxygen, the aerobic microbes metabolize
the pyruvate through the Krebs cycle. In the Krebs cycle the pyruvate is
converted into different organic acids like citric, oxalic, succinic acid, etc.
However, in absence of oxygen the pyruvic acid is fermented to either
alcohol or lactic acid.
The organic acids produced by microbial metabolism have several
functional properties. Acetic acid is a weak acid used as a preservative and
a food additive. It is soluble in lipids and therefore it can diffuse through
the plasma membrane of a microbial cell and affect its internal pH, causing
the death of food spoiling or pathogenic microorganisms (Giannattasio et
al. 2013). Citric acid is a preservative and flavoring agent generally used
in food and pharmaceutical industries. This acid acts as a chelating agent
for the metal ions present in the medium and inhibit microbial growth.
Pyruvic acid is also applied as a flavoring agent and as a preservative agent
(Nielsen et al. 2014, Theron and Lues 2011). Lactic acid is also a preservative
and a pH regulating agent (Theron and Lues 2011). Propionic acid is used
as a preservative and as a flavoring agent (Nielsen 2004). Hence, due to
the production of the above organic metabolites during milk fermentation,
the fermented milk products have long shelf life. In addition to the above
metabolites, exopolysaccharides are also formed by the microorganisms
found in kefir and koumiss. The microorganisms belonging to the genera
of Lactobacillus and Lactococcus are the mostly exopolysaccharide producing
bacterial strains in kefir (Welman and Maddox 2003, Irigoyen et al. 2005,
Miguel et al. 2010).
Kefir and koumiss contain complex microbial community which include
bacterial strains dominated by LAB, acetic acid bacteria and yeast strains.
The bacteria and yeast symbiotically exist in kefir, and the yeast strains
play the major role in the development of specific aroma and flavor. Lactic
acid bacteria are the prevalent bacterial strain found in the kefir grains.

410 Fermented Foods—Part II: Technological Interventions
The yeast cells do not grow efficiently when the bacteria are separated
from the kefir grain (Leite et al. 2013). Since some strains of yeasts such
as Saccharomyces cerevisiae, Saccharomyces turicensis, Torulaspora delbrueckii,
Kazachstania unispora, etc. found in kefir are unable to metabolize lactose
(Leite et al. 2013). This inability makes them dependent on the lactic acid
bacteria, which are capable of metabolizing the milk sugar lactose.
Kefir is usually made from partially skimmed cow’s milk. The final
product contains live bacteria and yeasts that produce carbon dioxide gas.
This gas production gives kefir a “sparkling” sensation on the tongue when
consumed. Kefir has been referred to as the champagne of fermented dairy
products.
Koumiss is a milk drink with a sharp alcohol and acidic taste (Salimei
and Fantuz 2012). The lactic acid content of koumiss varies from 0.7 to 1.8%
and the ethanol content varies between 0.6 to 2.5%. Koumiss is categorized
into mild, medium and strong depending upon the degree of lactic acid
and ethanol content. Due to higher alcoholic content the koumiss is referred
as milk wine.
6. Health Benecial Properties of Ker and Koumiss
Kefir and koumiss are microbial fermented milk products. The fermentation
process induces changes in the nutritional value, flavor, aroma and color, etc.
of the milk. The intake of kefir and koumiss promote wide range of health
benefits. Primarily, they are rich probiotic food for human consumption.
In addition to their probiotic nature they possess a wide range of health
benefits such as anti-bacterial and anti-fungal properties, regulate immunity,
maintain healthy gastrointestinal system, regulate cholesterol and sugar
levels, regulate blood pressure, help to get rid over the lactose intolerance,
induce production of some essential vitamins, etc. (Bakir et al. 2015,
Apostolidis et al. 2007). Recent studies that have focused on the importance
of probiotic food materials have enumerated the following points to describe
the health benefits achieved from kefir and koumiss consumption.
6.1 Ker and Koumiss as potential source of probiotics
According to The Food and Agriculture Organization of the United Nations/
World Health Organization (FAO/WHO 2001), the term probiotics can be
defined as “live microorganisms administered in an adequate quantity that
continue to exist in the intestinal environment, to perform a health positive
effect on the host” (Reid et al. 2003). The kefir and koumiss are excellent
source of probiotic microorganisms.
The microbes present in the kefir and koumiss live symbiotically, yet
the microbial population composition in them may differ due to the origins,

Kefir and Koumiss: Origin, Health Benefits and Current Status of Knowledge
411
methods and substrates used for preparation of these products. However,
there are common species of microorganisms such as bacterial strains of
Lactobacillus acidophilus, Lb. brevis, Lb. casei, Lb. fermentum, Bifidobacterium
bifidum, B. adolescentis, Streptococcus lactis, Str. alivarius, Str. thermophilus,
Bacillus, Enterococcus and yeast and mold strains of Saccharomyces
cerevisiae, S. bourlardii, Aspergillus niger, A. oryzae, Candida pintolopesii, etc.
Most of the probiotic bacterial strains colonize in the digestive tract
of our body. The widely known probiotic microorganisms belong to
bacterial strains of Lactobacillus and Bifidobacterium, however, bacterial
strains belonging to Pediococcus, Lactococcus, Bacillus and several strains
of yeasts are also reported for their probiotic nature (Soccol et al. 2010,
Blaiotta et al. 2013). The bacterial strains of Lactobacillus, i.e., LAB strains
are dominant microorganisms distributed throughout the gastrointestinal
and genital tracts of man and higher animals. They are non-pathogenic and
produce lactic acid by their metabolism; as a result they lower the pH of
the gastric and genital tract of human body. This class of microorganisms
also produce hydrogen peroxide, ethanol and/or acetic acid, thus inhibiting
the proliferation of unwanted pathogenic microorganisms in the gastric
and genital tract of the body. That is why these microorganisms are called
natural living protectors of the human body.
6.2 Ker and Koumiss has potent antimicrobial properties
The nutritional and organoleptic properties of the probiotic milk kefir
and koumiss offer the potential to combat against pathogenic microbial
infections (Franco et al. 2013, Carasi et al. 2014, Silva et al. 2009). Recent
scientific studies have confirmed the antimicrobial properties of traditional
kefir and koumiss. In a study, Chifiriuc et al. (2011) evaluated the
antimicrobial properties of kefir by in vitro analysis. The authors investigated
the antimicrobial activity of kefir against the bacterial strains of the Bacillus
subtilis, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Salmonella
enteritidis, Pseudomonas aeruginosa and Candida albicans. They compared the
antimicrobial properties of the kefir fermented for 24 hr and 48 hr, as well
as 7 day old preserved kefir by in vitro disk diffusion method. The authors
compared the antimicrobial activities of the kefir with those of the antibiotics
ampicillin and neomycin and observed higher antimicrobial potential of
kefirs against the bacterial strains used for the study. The authors claim
that the kefir has higher antibacterial properties when compared to control
antibiotics (ampicillin and neomycin) taken for the study.
A recent study of the antimicrobial properties of the koumiss was
conducted by Chen et al. (2015). The authors used koumiss from Inner
Mongolia, China and evaluated the anti-bacterial properties of the
mycotoxin secreted by the yeast cell of koumiss by in vitro and in vivo

412 Fermented Foods—Part II: Technological Interventions
analysis. Through genomic analysis, the authors identified three strains of
S. cerevisiae, and two strains of Kluyveromyces marxianus producing mycocin
in the traditional Koumiss from Inner Mongolia. The in vitro and in vivo
study on mice confirmed the anti-bacterial properties of the mycotoxin
isolated from the yeast cells of koumiss against the pathogenic E. coli
bacteria. Hence, the study shows that the traditional fermented milk
beverages have potential antimicrobial properties.
6.3 Ker and koumiss as a substitute for lactose intolerant people
Lactose is a naturally occurring sugar in milk. Most of the adult populations
of the world are unable to digest the lactose content of the milk properly.
Such condition of lactose indigestion is called lactose intolerance. The LAB
present in kefir and koumiss ferment lactose to lactic acid, and as a result
these dairy foods are much lower in lactose content than raw milk. Hence,
in general kefir and koumiss are well tolerated by the people with lactose
intolerance in comparison to regular raw milk products (Fox et al. 2015,
Zubillaga et al. 2001).
6.4 Ker and koumiss stimulate expression of growth factors
In the recent in vivo study conducted on mice model by Bakir et al. (2014) it
was revealed that the probiotic dairy products positively affect the release
of growth factors and stimulates the increase in body weight of mice. The
authors conducted immune-histochemical studies on the liver and kidney
cells on the mice nourished with kefir and koumiss and observed the
expression of the platelet derived growth factor-c (PDGF-C) and platelet
derived growth factor receptor-alpha (PDGFR-α). The authors found that
PDGF-C and PDGFR-α were expressed more in the kidney cells and hepatic
cells and stimulated increase in live weights of the mice models used for
the study. The platelet derived growth factor receptor-alpha (PDGFR-α) is
a member of the PDGF receptor and they play a vital role for activation
of platelet derived growth factor (Andrae et al. 2008). The platelet derived
growth factors (PDGF) are a class of growth factors that influence growth
and development of body. From the above report it may be concluded
that the probiotic dairy products kefir and koumiss act as growth and
development promoters.
6.5 Ker may be protective against cancer
Cancer is one of the world’s leading causes of death. It occurs when there
is an uncontrolled growth of abnormal cells in the body such as a tumor.
The probiotics in fermented dairy products are believed to inhibit tumor

Kefir and Koumiss: Origin, Health Benefits and Current Status of Knowledge
413
growth by reducing formation of carcinogenic compounds, as well as by
stimulating the immune system (Leite et al. 2013).
6.6 Trends in Transformation of Traditional Ker and Koumiss to
commercialization
According to a market survey conducted by Transparency Market Research,
the global sale of probiotic products is $15.9 billion in 2019 as compared
to $11.6 billion in 2012. Although kefir is not known in all corners of the
world, still it has a stake among the probiotic products. A company named
Lifeway Foods, Inc, recently named one of Fortune Small Business Fastest
Growing Companies, is known to sell of $100 million annually. In 2013 the
company introduced the products to the UK and subsequently to Canada.
The products are available in different flavors such as vanilla, raspberry,
strawberry and mango flavors. Some of the kefir products of Lifeway Foods
have been displayed in Fig. 4. More than 1000 leading stores such as Kroger,
Wegmans and Whole Foods are known to sell kefir in the US. However the
Figure 4. Kefir with different flavours marketed by Lifeway industries.
(source: http://lifewaykefir.com/).

414 Fermented Foods—Part II: Technological Interventions
commercialization of koumiss is not clearly documented. Unlike kefir the
commercialization of koumiss is difficult as the substrate for the koumiss,
i.e., mare’s milk is rarely available.
7. Conclusion
Fermented dairy products such as kefir and koumiss have numerous
functional properties. It is a convenient and traditional process of food
preservation. Fermentation lowers down the pH of milk and inhibits
the growth of food spoilage microorganisms. The microbial metabolites
like different organic acids, exopolysaccharides produced during kefir
and koumiss production enhances their flavor, aroma and texture, which
are attractive for the consumer. This chapter has described the history,
microbiology and biochemistry of kefir and koumiss. The current market
status of the two products has been mentioned. Popularization of kefir
and koumiss can be expedited through deliberation and discussion of the
health beneficial properties of the products in different forums such as social
media, internet, etc. Future research should be directed to upscale and for
the commercialization of kefir and koumiss, keeping in view the health
beneficial properties and unique organoleptic properties of the products.
Keywords: Kefir, koumiss, milk, fermentation, probiotics
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