FERMENTATION. 



PAGE 



THE PREPARATION OF PURE-CULTIVATED YEASTS ON A 



LARGE SCALE 25 



Preliminary work . . . . . . . . . . . . . . . . 25 



The sample to be tested for wild yeast is best taken at the end of 

 the primary fermentation, and the sample to be used in the pre- 

 paration of the desired pure culture of the brewery yeast is best 



taken at the commencement of the primary fermentation .. .. 25 



Temporary variation .. .. .. .. .. .. .. 28 



Duration of vitality of yeast cells in wort, cane sugar solution and 



in filter paper . . . . . . . . . . . . . . . . 29 



Experience shows that a solution of cane sugar affords a good medium 



for the preservation of yeasts at the ordinary room- temperature .. 30 



My Old Method 31 



The sterilisation of wort in glass and metal vessels .. .. .. 3 1 



The thorough aeration of the wort is of especial importance . . 36 



Manipulations with pure yeast in the fermenting cellar . . . . 38 



The Pure Yeast Apparatus 40 



Description of the separate parts and instructions for the employment 



of the apparatus devised by Kiihle and myself .. .. .. 40 



Various modifications of the apparatus for low fermentation . . 58 



For high fermentation . . . . . . . . . . . . . . 62 



Cost of the apparatus 63 



Filters 64 



Chamberland's porcelain filters . . . . . . . . . . . . 65 



Schroder and Dusch's cotton- wool filters .. .. .. .. 66 



The filters of the pure yeast apparatus . . . . . . . . 66 



Their efficiency . . . . . . . . . . . . . . . . 68 



The Introduction of the Yeast into the Propagating Apparatus and its 



Transport .. .. .. .. .. .. .. .. 7 



How the yeast is introduced into the apparatus 70 



Laboratories in which my methods are carried out .. .. .. 7 1 



Course for students in Carlsberg laboratory .. .. .. .. 7 1 



Methods for transmitting pure cultivated yeasts . . . . . . 7 2 



CHAPTER II. 



RESEARCHES ON YEASTS. 



I. CHARACTERISTICS OF THE SACCHAROMYCETES 77 



Development and germination of spores j film-formation ; form of 

 the cells under certain conditions of cultivation ; behaviour with 

 regard to the carbohydrates .. .. .. .. .. .. 77 



Difference between the spore contents of the culture yeasts as com- 

 pared with the wild yeasts .. .. .. .. .. .. 78 



Recent investigations on the origin of the Saccharomycetes .. .. 81 



