MALT LIQUORS. 



273 



yeast. These different varieties have been shown to produce beers dif- 

 fering not only in coloring, flavoring, facility of separation of the yeast, 

 &c., but also in chemical composition. 



In a recent address before the Society of Chemical Industry by G. H. 

 Morris, 1 a resume is given of the work done in this direction by Hansen 

 and others. 



Dr. Morris states that the employment of the pure yeasts is coining 

 very largely into use in the beer-drinking countries of the Continent, 

 and has met with favor from some of the most noted brewing technol- 

 ogists, such as Jacobson, Aubry, Miirz, and Liutner, the latter of whom 

 sums up the question in the following statements : 



(1) By contamination with so-called wild yeast an otherwise normal brewery yeast 

 can be rendered incapable of producing a beer of good flavor and with good 

 keeping qualities. 



(2) A contamination with wild yeasts may be produced by the dust of the air during 

 summer and autumn, by the malt, or other sources. 



(3) By employing Hanson's method of pure cultivation and analysis it is possible to 



obtain from a contaminated yeast a good brewery yeast in a state of purity. 



(4) Yeast cultivated in a state of purity possesses in a marked degree the properties 



of the original yeast before contamination as far as concerns the degree of 

 alteration of the flavor and keeping qualities of the beer. 



(5) There exist different varieties of normal bottom yeast (S.ccreris.), each with 



special properties which, like the peculiarities of species, are maintained con- 

 stant. 



The use of this yeast has not yet extended to England, although ex- 

 periments on an industrial scale are now being carried on at Burton- 

 ou-Treut with different species of pure yeast. 



The chemical characteristics of beer made from the different species 

 of pure yeast have been investigated by Borgmann, 2 who analyzed sam- 

 ples of beer produced from two species of pure yeast, each cultivated 

 from a single cell and the beer fermented under comparable conditions. 

 The analysis gave the following results : 



From these numbers, which are the means of many determinations, the 

 analyst concludes that the different yeasts produce beers which differ 

 in chemical composition. He also finds that the proportion of alcohol 



1 Jour. Soc. Chem. Ind., 1887, p. 113. 



2 Zeit. Anal. Chem. 25, 532, 



