THE FERMENTING POWER OF PURE YEASTS 

 AND SOME ASSOCIATED FUNGI. 



INTRODUCTION. 



The use of selected pure yeast cultures has become a common prac- 

 tice in certain r'ndustries, notably in brewing and distilling, and their 

 value in other lines, as in cider manufacture and in bread making, is 

 now recognized. Selected, pure races of yeasts have come into much 

 more general use in the cider industry in Germany than in other 

 countries, and when employed with the proper technique they have 

 been found very beneficial. Their use in this industry has been prac- 

 ticed to a considerable extent for some years past in France, and less 

 extensively in this country, yet there is every reason to believe that 

 the industry would be greatly benefited by their employment. 



As special agent of the Bureau of Chemistry the writer collected 

 from foreign laboratories a number of tested yeasts and has also iso- 

 lated a considerable number of yeasts from native and foreign sources. 

 These have been tested in the fermenting of apple juice for several 

 years past, incidentally in connection with other investigations, and 

 pure yeast cultures have also been distributed quite widely in the 

 United States for the past six years, some of which seem to be valu- 

 able for cider making. A description of these yeasts is given on 

 page 25. 



There is, however, a very large amount of work necessary on the 

 practical details, as well as more critical scientific investigation, be- 

 fore pure yeast cultures can be sent to local manufacturers with a 

 fully developed plan for their use in ordinary factory work. In fact, 

 the question greatly needs at this time the assistance of well-equipped 

 cider manufacturers in working out many details, and to those who 

 wish to experiment with special yeast cultures these will be furnished, 

 together with such data and instructions as are obtained in the experi- 

 mental work. 



TESTING PURE YEASTS. 



The fact that a ^east is a pure culture does not settle the question 

 of its value for cider making, hence when an apparently desirable 



22050 Bull. 11108 2 7 



