4
STUDIES ON DAHI: I. INTRODUCTION
[Vol. XXII, Part I,
preparing Huslanka [Olsen-Sopp, 1912; Heinemann, 1911]. Taette is a sour milk
used in Scandinavia and in which a slimy fermentation is caused by a variant of
S. lactis called S. taette (probably S. lactis var. hollandicus). Piimae is a similar
product prepared from skim milk in Finland [Gasser, 1931]. Saya is prepared in
the East from unheated milk by first ripening with S. lactis and later with lacto-
bacilli. A considerable amount of gas (probably CO 2 ) is produced and proteolysis
also occurs [Gasser, 1931; The Associates of Rogers, 1935].
The second group of fermented milks includes Kefir, Leben, Koumiss, and
other less known products. Of these Kefir (or Kephyr) is one of the oldest varieties
of fermented milk manufactured from the milk of cows, sheep or goats. It is
believed to form a considerable part of the food of mountain dwellers of the Caucasus
region, who prepare it in leather bottles made from goat skin. In this product the
fermentation is brought about by Kefir grains which resemble miniature cauliflowers
in shape and structure and consist of casein, yeasts and bacteria. Various species
of microorganisms have been isolated from Kefir, e. g., S. lactis, S. kefir, Dispora
caucasica (L. caucasicum Beijerinck), Streptobacterium casei, Saccharomyces kefir,
lactose fermenting torulae, Oidium lactis, Bacillus subtilis and butyric acid bacteria
[Corminboeuf, 1933, Burke, 1940, Orla Jensen, 1942, Tanner, 1944]. The lactic
acid bacteria produce lactic acid while the yeasts produce about 1 to 1.2 per cent
alcohol. Occasionally organisms resembling B. coli and B. cloacae are also said to
be present and they produce gas as well as a slimy consistency in the kefir. The
fermentation is usually carried out in closed bottles so that the gas is retained and
the milk becomes effervescent. Koumiss (Kumys), used extensively in Siberia,
Central Asia and Southern Russia, is also prepared by a preliminary acidic and
subsequent alcoholic fermentation of unpasteurised mare's milk. It has a higher
concentration of alcohol (about 3 per cent) than Kefir and is a highly effervescent
drink. The fermentation is due to L. bulgaricus principally while lactose fermenting
torulae and Bacterium lactis acidi (Leichmann) play a secondary part [Voitkevich,
1934; Tanner, 1944]. Pauira, a product similar to Koumiss is used in Lapland
[Gasser, 1931]. Kuban, a product used in Southern Russia is made from pasteu-
rised milk by a combined lactic and alcoholic fermentation. The microflora include
a lactic streptococcus resembling S. lactis var. hollandicus, a lactic acid rod of the
L. bulgaricus type and three types of yeasts [Bogdanoff, 1934]. Leben is another
fermented milk prepared by Egyptians from the milk of cows, goats or buffaloes
and the fermentation is brought about by the joint action of lactic acid bacteria
and yeasts [Khoury and Rist, 1902]. Kaelder-milk (cellar milk) is a Norwegian
product prepared by inoculating boiled milk with a special variety of ropy milk
and keeping it cold. Large quantities of lactic acid (2.5 per cent) and some alcohol
(0.5 per cent) are formed which enable the product to keep well [Rettger, 1923].
It is often used as a substitute for fresh milk by Norwegian peasants. Urda is a
strongly alcoholic beverage prepared in the Carpathians from sheep's milk, and
sometimes known as Sparkling whey. Whey champagne or Skuta is a similar
product prepared in Chile by the fermentation of whey through the agency of
lactose fermenting yeasts and some species of lactic acid bacteria [Rettger, 1923 ;
Harvey and Hill, 1948]. Another variety of fermented milk containing up to
0.78 per cent of lactic acid and 7.1 per cent of alcohol is used in Turkestan under
the name Busa [Chekan, 1922].