RELATION OF MICROORGANISMS TO SOME SPECIAL DAIRY PRODUCTS. 369 



plated in gelatin without difficulty but it was very difficult to grow the 

 other two organisms present on any artificial media. He concluded that 

 the yeasts present in kefir are not identical with the species commonly used 

 in making beer and named it Saccharomyces kefir. The streptococcus 

 curdled milk in less than forty-eight hours at a temperature of 37 but the 

 micrococcus did not curdle milk at all, although it produced a consider- 

 able amount of acid. 



De Freudenreich changed the name of the bacillus from Dispora caucasica, 

 given it by Kern to B. caucasicus, because it did not produce spores as Kern sup- 

 posed. He also found that this organism would not grow at all on media without 

 sugar, very slightly on milk, serum, agar, and best of all in milk, in which it produces 

 both gas and acid without curdling the milk. This organism is 5 jj. or 6 fj. in length 

 by i j in width, is slightly motile and retains Gram's stain. It has a thermal death- 

 point of 55 for five minutes. 



The preparation of good kefir seems to depend upon the combined 

 action of the four types of organisms described. Kefir is sometimes 

 prepared without the use of the kefir grains* by placing milk in bottles 

 to which is added a small amount of compressed yeast and sucrose. The 

 bottles are then held at a temperature of 10 to 15 about fifteen hours 

 and shaken occasionally. Kefir prepared in this way gives an effervescent 

 mild flavored drink. 



LEBEN. For centuries the Egyptians have used a fermented milk 

 drink known as leben or leben raib. This was prepared from the milk of 

 cows, buffaloes, and goats. In general it resembles the other fermented 

 milk drinks in the fact that the fermentation is produced by yeasts and a 

 variety of other microorganisms working together. At least one yeast 

 and three species of bacteria seem to be normal to this product. A 

 fermented milk drink very similar to leben is also used in Algeria. Just 

 the action of each microorganism concerned in the fermentation of this 

 product is not certain, but it is probable that all of the species are essential 

 for the production of the particular flavor and consistency of the fermented 

 product. It is claimed that the fermentation that takes place in the milk 

 renders it more digestible than raw milk. For this reason it is recom- 

 mended for the use of invalids and persons having weak digestion. 



YAHOURTH OR MATZOON (YOGURT, YAHOURD, MADZOON, ETC.). A 

 fermented milk drink known by one of the above names has been used 

 by the Bulgarian tribes for a long time. It has recently been studied and 



* Milch Zeitung, 1888, p. 393. 

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