Storage of the koumiss upon ice or in a cellar is necessary since medium koumiss is converted to strong koumiss in twelve to sixteen hours at ordinary temperatures, while at the lower temperature this occurs only in two to four days.[60]
According to Biel,[61] either old koumiss or the dried sediment from old koumiss may be used for the initial inoculation. It may also be prepared by the repeated inoculation of mares' milk with soured cows' milk until a fermenting product is obtained. Koumiss may be prepared by a method stated by Allik[62] to be in general use in the Caucasian health-resorts. One part of beer-yeast is added to four to ten parts of fresh mares' milk (according to the strength of product required), and after thorough mixture of the two liquids the whole is allowed to ferment at a temperature of 70° to 72° F. for two days. One part of this first product is then added to five parts of fresh cold milk, and allowed to stand three to four hours at 75° to 77° F. It is then poured into bottles, and after the expiration of another three to four hours is stored away in a cellar at about 45° F. This koumiss may be used at any time from one to five days (generally two to three) after bottling according to the strength desired or prescribed in each individual case.
The changes undergone during fermentation consist in a vigorous gas and acid production accompanied by alcohol formation and coagulation of the milk. The coagulum exists in an extremely fine state of division, and the liquid froths violently on the bottle being opened. It has a full pleasant acid taste, but should not contain more than one per cent. acid and two per cent. alcohol. The specific gravity of koumiss is 1.008 to 1.020 at 60° F. Appended is an analysis of two different samples of koumiss:
| Prepared from | ||
| Mares' Milk. | Separated Cows' Milk. | |
| Per Cent. | Per Cent. | |
| Water | 91.535 | 88.933 |
| Fat | 1.274 | 0.854 |
| Nitrogenous bodies | 1.913 | 2.025 |
| Sugar | 1.253 | 3.108 |
| Ash | 0.293 | 0.444 |
| Carbon dioxide | 0.876 | 1.027 |
| Alcohol | 1.850 | 2.647 |
| Lactic acid | 1.006 | 0.796 |
| Glycerine | ... | 0.166 |
Fleischmann[63] gives a formula for preparing an artificial koumiss from separated cows' milk, water, cane sugar, and milk sugar, with the addition of distillery yeast. Needless to say, this product must possess some of the characteristic by-flavour of the yeast employed, and is less suitable than koumiss prepared by the aid of a lactic yeast. Schipin investigated the fermentation of koumiss and found three distinct organisms.
Rubinsky in a recent article threw much light on the phenomena of koumiss fermentation. According to him, koumiss contains almost invariably four different organisms, viz., koumiss yeast, koumiss bacterium (Lactobacillus), Streptococcus lactis (Lister), Bacterium aërogenes, and occasionally Bact. caucasicum (Nikolajewa). For the preparation of normal koumiss only the two former organisms are required; they exceed in number any of the other organisms whose presence in the dairy is unavoidable. The presence of the two latter organisms is favourable to the production of good koumiss, as, by inducing a preliminary lactic fermentation, they tend to inhibit the growth of undesirable extraneous bacteria, etc. In medium and strong koumiss they die out on account of the amount of lactic acid formed (1%).
Koumiss yeast possesses strongly differentiated protoplasm, but lacks any cultural characteristics. Abundant growth occurs in milk, and lactic acid (0.3%), alcohol, carbon dioxide, albumens and peptones, volatile acids, and aromatic substances are formed.
Koumiss bacterium is related to the Lactobacillus of various other fermented milks, and is similar to Bac. acidophilus, and possesses like these a distinct polymorphism (branched cells, long and short bacilli, etc.). It is non-sporogenous, has an optimum temperature of 90° to 97° F., and possesses cultural characteristics similar to those of the rest of the Lactobacilli.
The by-products of koumiss yeast appear to favour the growth of the koumiss bacterium, as this organism, like the other Lactobacilli, is favourably influenced by the presence of small quantities of peptone, alcohol, and acid.
The organisms found by Schipin consisted of a species of Saccharomyces and two bacilli, Bacillus acidi lactici and a non-sporulating bacillus. The latter organisms coagulate milk at 98° F., but not at room temperature, and although a minute description of cultural characteristics is not given it would seem to be related to Bacillus or Lactobacillus caucasicus.