BLBS102-c26 BLBS102-Simpson March 21, 2012 13:51 Trim: 276mm X 219mm Printer Name: Yet to Come
518 Part 4: Milkin combination with a lactic acid fermentation (Tamine and Mar-
shall 1984). The conversion of milk into a fermented product has
several important advantages; as well as being a means of preser-
vation, it also improves taste and digestibility and increases the
variety of food. Current interest in the health benefits of fer-
mented milks started with the theory of longevity proposed by
the Russian microbiologist, Elie Metchnikoff (1845–1918); he
claimed that people who consumed fermented milks lived longer
as lactic acid bacteria from the fermented product colonised the
intestine and inhibited ‘putrefaction’ caused by harmful bacte-
ria (a probiotic effect), thereby slowing down the aging process.
Nowadays, the principal effects of probiotics are thought to be:
improved gastrointestinal transit time of digesta, bowel func-
tion and glycemic index; some reports claim that they have an
anticarcinogenic effect (see McIntosh 1996).
Further details on the fermentation of milk can be found in
many publications including: Tamine and Marshall (1984); Ko-
roleva (1991); Kurmann et al. (1992); Nakazawa and Hosono
(1992); Surono and Hosono (2002).KoumissKoumiss (Kumys), fermented equine milk, is widely consumed
in Russia, Mongolia and Kazakhstan, primarily for its therapeu-
tic value. Russians, in particular, have long advocated the use of
koumiss for a wide variety of illnesses but the variable micro-
biology of these products has made it difficult to confirm any
theoretical basis for the claims (Tamine and Robinson 1999).
In Mongolia, koumiss is the national drink (Airag) and a high-
alcoholic drink made by distilling koumiss, called Arkhi, is also
produced (Kanbe 1992).Per caputconsumption of koumiss in
Mongolia is estimated to be about 50 L/yr.
Koumiss is still manufactured in remote areas of Mongolia
by traditional methods but with increased demand elsewhere it
is now produced under more controlled and regulated condi-
tions. Traditional koumiss (from fresh raw milk) was prepared
by seeding milk with a mixture of bacteria and yeasts using part
of the previous day’s product as an inoculum. The milk was
held in a leather sack called a ‘turdusk’ (also called a ‘saba’ or
‘burduk’), made from smoked horsehide taken from the thigh
area, that is, it has a broad bottom and a narrow, long, sleeve
with a capacity of 25–30 L, fermentation takes from 3 to 8
hours. In the 1960s, the microbial population was analysed and
found to consist mainly ofLactobacillus delbrueckiisubsp.bul-
garicus,Lactobacillus casei,Lactococcus lactissubsp.lactis,
Kluveromyces fragilisandSaccharomyces unisporus(Tamine
and Marshall 1984). The lactic acid bacteria are responsible for
acid production and the yeasts for the production of ethanol and
carbon dioxide. During the mixing and maturation stages of pro-
duction, more equine milk is usually added to control the levels
of acidity and ethanol. The whole process is poorly controlled
and often results in a product with an unpleasant taste due to the
presence of too much yeast or excessive acidification. Turdusks,
often containing fermented caprine milk from the previous sea-
son, were stored in a cool place over winter and the culture was
reactivated when required by gradually filling the turdusk with
equine milk over about 5 days (Tamine and Marshall 1984).Koumiss contains about 90% moisture, 2–2.5% protein (1.2%
casein and 0.9% whey proteins), 4.5–5.5% lactose, 1–1.3% fat
and 0.4–0.7% ash, as well as the end-products of microbial
fermentation, that is, lactic acid (1.8%), ethanol (0.6–2.5%)
and CO 2 (0.5–0.9%) and provides 37 to 40 kCal/100 mL). Af-
ter production, koumiss contains between 0.6 and 3% ethanol
and is effervescent. Koumiss is thought to be more effective
than raw equine milk in disease treatment due to the additional
peptides and bactericidal substances produced during microbial
metabolism (Doreau and Martin-Rosset 2002).
In the last decade, technological advances have been made in
the manufacture of koumiss, such as the development of blends
of microorganisms in starter cultures that enhance flavour devel-
opment and extend the shelf life up to 14 days. The production of
koumiss and other fermented milk products is carried out using
a more standardised protocol for manufacture and is of con-
siderable interest for increasing the market and consumption of
equine milk products in countries where it has not normally been
consumed (Di Cagno et al. 2004). As well as pasteurising the raw
equine milk, pure cultures of lactobacilli such asLb. delbrueckii
subsp.bulgaricusand yeasts are used for koumiss manufacture.
The use ofSaccharomyces lactisis considered best for ethanol
production (2–5%) andS. cartilaginosusis sometimes used for
its antibiotic activity againstMycobacterium tuberculosis(Park
et al. 2006). Other microorganisms such asCandidaspp.,Torula
spp.,Lb. acidophilusandLb. lactismay also be used in koumiss
production (Surono and Hosono 2002). A protocol for the man-
ufacture of commercial koumiss is presented in Figure 26.6.
The characteristics of a good koumiss are optimal when lac-
tic and alcoholic fermentations proceed simultaneously so that
the products of fermentation occur in definite proportions. As
well as lactic acid, ethanol and CO 2 , volatile acids and other
compounds are formed which are important for aroma and taste
and approximately 10% of equine milk proteins are hydrolysed.
Products with varying amounts of lactic acid and ethanol are pro-
duced and generally 3 categories of koumiss are recognised: mild
(0.6–0.8% acidity, 0.7–1.0% alcohol; medium (0.8–1.0% acid-
ity, 1.1–1.8% alcohol) and strong (1.0–1.2% acidity, 1.8–2.5%
alcohol (Tamine and Marshall 1984).
The presence of a high level of thermostable Lyz in equine
milk may interfere with the activity of some starter microor-
ganisms in the production of fermented products and thus cause
problems in the processing of equine milk. Di Cagno et al.
(2004) who heated equine milk to 90◦C for 3 minutes to inacti-
vate Lyz, produced an acceptable fermented product. In sensory
tests, fermented equine milk generally scores low and, in an at-
tempt to enhance the rheological and sensory properties of fer-
mented products made from equine milk, Di Cagno et al. (2004)
fortified equine milk with bovine Na caseinate (1.5 g.100−^1 g),
pectin (0.25 g.100−^1 g) and threonine (0.08 g.100−^1 g). The re-
sultant product had good microbiological, rheological and sen-
sory characteristics after 45 days at 4◦C. Fermented unmodified
equine milk had an unacceptable viscosity and scored very low
in comparison to fortified products for appearance, consistency
and taste.
Research has turned also to producing koumiss-like products
from bovine milk, which must be modified to make it suitable for