Fig. 12—Streptococcus lacticus (Grotenfeldt) growing on lactose-agar, stained by Gram's method. ( ✕ 900 diams.)
Diseases of Keffir Grains.—According to the age and the previous treatment to which keffir grains have been subjected, the vitality of one or more of the organisms constituting the grain may have been impaired. The results of Freudenreich have shown that Saccharomyces keffir and Streptococcus a are unable to withstand desiccation for more than a few days, and this is sufficient to account for the frequent failures to obtain normal keffir from the grain. Further, grains succumb to a mucilaginous disease; the cavities become filled with a slimy fluid, and the grains are covered with mucilaginous matter. They lose their elasticity and become brittle or mealy, but large grains appear to be more subject to this fault than do the small ones. Such grains should be disinfected by immersion for a short time in two per cent. salicylic acid solution, followed by drying in the sun, whereby they are completely regenerated.
Another disease consists in the predominance of certain butyric acid bacteria which impart an unpleasant rancid taste to the keffir (Podowyssozki). This is generally attributed to the use of rich milk, or too high a temperature during preparation.
Koumiss.—Another product of the combined action of lactic acid and alcohol-producing organisms is called koumiss, kumys, milk-wine, lac fermentation, or vinum lactis. In the steppes of Southern Russia and Asia, as we have seen,[59] it is prepared chiefly from mares' milk, but occasionally from that of camels and jennets. The name is said to be derived from that of a tribe mentioned by Xenophon and Pliny, viz., the Kumanen, by whom its preparation was practised. After the war with the Tartars in 1215 its use was adopted by the latter people, and eventually spread to the Turkomanen, Kalmucks, Khirgiz, Mongolians, etc.
Rubruck, in 1253, records the use of a fermented drink—kosmos—prepared from mares' milk, and about the same time Marco Polo mentions the occurrence of a milk-wine, chumis or chemius, among the Tartars. The fact that the Tartars were seldom ill, and were almost invariably free from lung troubles, led to an influx of visitors from surrounding countries, until finally its use spread to Russia, Austria, and Germany. At the present time the best koumiss is that produced in the province of Orenburg; but specially equipped koumiss establishments, under the control of physicians, exist in Odessa, Samara, Ufa in the Urals, and other districts. The curative properties of koumiss have long been recognised and its use is indicated in cases of indigestion, chlorosis, scurvy, tuberculosis, etc.
Rubinsky states that, among the nomadic tribe, of Khirgiz and Kalmucks, a special leathern bottle (Turssuk, Orroth, or Soaba) is used for the preparation of koumiss, while wooden tubs (Tschiljak) similar in shape to the old-fashioned churn are used by the Bashkirs, and in koumiss establishments.
The fermentation is induced by the addition of koumiss to fresh mares' milk, in proportions which vary according to the cleanliness observed in the actual preparation. Where the process is carefully controlled, one part of koumiss to ten parts of milk is often used, but where gross infection from outside sources takes place one part of koumiss to three parts of milk is taken. The mixture is stirred at frequent intervals, and stored at a temperature of 73°-90° F. Weak koumiss is obtained after twenty to twenty-four hours in winter and twelve to fourteen hours in summer, but is scarcely ever consumed immediately, as it possesses a strong purgative action.
It is generally poured into bottles (bottled koumiss); or allowed to remain in the tubs (tschiljak koumiss); in the former case the fermentation is anaërobic, in the second it is aërobic.