Science jpragress. 



No. 4. June, 1894. Vol. I. 



PURE YEAST AND ITS RELATIONS TO 

 BREWING OPERATIONS. 



1"* H E practical application of pure yeast in the brewery 

 must be considered to date from the year 1883, 

 when Professor Hansen first introduced a pure cultivation 

 of yeast into the Carlsberg Brewery at Copenhagen. 

 Although many years previously a method had been de- 

 scribed by Pasteur for the purification of brewers' yeast, 

 this method had for its object merely the removal of bac- 

 teria, which are always present in commercial yeast. In 

 fact, at the time when Pasteur made his experiments, it 

 was not known that many of the so-called "diseases" of 

 beer are caused, not by bacteria, but by certain races of 

 yeast, which are now commonly spoken of as " wild " types, 

 and it is indeed to Hansen that we are indebted for the 

 discovery of this fact. Hansen found that some of the 

 commonest "sicknesses" to which beer is subject are 

 caused by these objectionable races of yeast and that the 

 development of these was actually encouraged by the treat- 

 ment proposed by Pasteur. With the object, therefore, of 

 eliminating these and all other injurious organisms, the 

 Danish savant not only devised a method by means of 

 which it was possible to prepare absolutely pure cultiva- 

 tions of the different yeasts, but in conjunction with Cap- 

 tain Kuhle he also succeeded in devising an apparatus for 



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