FERMENTED MILKS 401 



formed slowly, and from maltose not at all. In beer wort the yeast 

 produced a somewhat slimy consistency. Owing to the high 

 temperature of fermentation the yeast probably grows reluctantly 

 in tatt6 melk, so that its products are present only in small quan- 

 tity. Oidium lactis is also found in this fermented milk and 

 probably causes the cheesy taste and odor. 



Different types of other micro-organisms are usually found in 

 tatt^ melk, but these have no bearing on the normal fermentation 

 and are of the kind usually found in milk. A lactobacillus can 

 also be found, but in relatively small numbers. The acidity of 

 the finished product is mild, and this fact shows that laetobacilli 

 grow but slowly, if at all. It is, however, not surprising to find 

 a member of the group of laetobacilli in tatt^ melk, since they 

 are universally present in cow's milk. 



A fermented milk of similar properties is prepared in the 

 Bretagne and is known as "Gros Lait." 



Fermented Milks of Pre-eminently Acid Fermentation 



The people inhabiting the Caucasus Mountains, Bulgaria, 

 Turkey, Egypt, Sardinia, Sicily, Armenia, Serbia, and Monte- 

 negro consider fermented milk a very important part of the daily 

 diet. Visitors are served with these milks, and some of the in- 

 habitants regard them with the reverence due divine gifts. The 

 milks of different tribes vary somewhat, but have much in com- 

 mon. The fresh milk is boiled usually over a slow fire, some- 

 times for a short time, sometimes long enough to reduce its vol- 

 ume materially. With the reduction of volume the percentage 

 of solids is proportionately increased, and the taste, therefore, 

 differs materially from that of other fermented milks. After 

 boiling the milk is cooled to 45° to 50° C, the temperature being 

 judged by dipping the fingers into the milk. A small amount of 

 a previously prepared milk is added as a starter and the mixture 

 then incubated for several hours. The temperature is maintained 

 by wrapping and covering the vessels with woolen cloths. 



Considerable work by eminent investigators has been carried 

 on to determine the active agents in these milks. The results 

 of this work show that there are always three types of organisms 

 present, and these are required to produce the normal product. 



The most important organism is a lactobacillus, variously 

 called Bacillus bulgaricus, Streptobacillus lebenis. Bacterium cau- 

 casicum, etc. The relatively high temperature of incubation fa- 

 vors the growth of this organism, and the final product has in large 

 measure the appearance, taste, and texture which is character- 

 istic of its activity in milk. All these fermented milks, when ripe, 



9.6 



