142 MORPHOLOGY AND LIFE-HISTORY OF YEASTS. 



70° C, an exposure of half-an-hour was required to kill the 

 vegetative cells, whilst the spores withstood the influence of 

 75° 0. for the same period. Antithetical to this is Sacch. 

 Jcergensenii, which was discovered by A. Lasche (I.) in a very 

 turbid American, so-called temperance ale, and quickly perishes 

 at temperatures above 30° 0. Similar experiments were made 

 with French wine yeasts by E. Wasserzug (II.) and southern 

 wine yeasts by Ed. Kayser (YII.), the latter of whom found 

 the fatal temperature for spores to be about 5° C. higher than 

 for vegetative cells. 



In order to ensure stability in fermented bevei'ages it is 

 sufficient to so far weaken the yeast cells by warmth as to pre- 

 clude subsequent repi'oduction, and thus practically eliminate 

 them. To attain this end, experience has shown that the ne- 

 cessary influence must be less stringent than is required for 

 killing the cells ; and the case is facilitated when the liquid 

 contains substances which, like alcohol and acids, exercise an 

 injurious effect on yeasts and bacteria at a somewhat higher 

 temperature than the normal. These latter conditions are ful- 

 filled in the case of wine, beer, and wine-must, and an 

 explanation is thus afforded of the fact that these liquids can 

 be converted into a stable condition by a gentle heat, consider- 

 ably below boUing point. The earliest application of such a 

 process is traceable to the Japanese. According to 0. Kokschelt 

 (I.), the Japanese rice beei', or sake (already mentioned in an 

 earlier paragraph), is made to keep through the hot summer 

 months by warming, a practice that has been pursued for more 

 than a century. The first to adopt such a method in Europe 

 was Scheele in 1782 (§ 11) ; and Appert, in 1810, recommended 

 the warming of wine, in corked bottles, to 75° 0. It was, how- 

 ever, soon found that this treatment injured the fine flavour, 

 especially in the case of red wines. Then, in 1865, Yergnette- 

 Lamotte (I.) proposed to employ a temperature not exceeding 

 50° 0., thereby avoiding the evil specified without missing the 

 principal object in view ; and at the same period Pasteur (XX.), 

 as a result of his researches on wines, found that they could be 

 reliably protected against deterioration by warming them up to 

 55° to 60° C. With regard to the priority dispute between the 

 two authorities, the reader is referred to the bibliography. 

 Thanks to the reputation at that time enjoyed by Pasteur, the 

 process patented by him was quickly introduced into practice, 

 and called Pasteurisation in his honour. 



The inventor's primai'y intention was to use this process 

 merely for imparting stability to wine, the killing or permanent 

 weakening of the germs therein being effected by the conjoint 

 influence of a temperature of 55° to 60° C. (in itself insufficient 

 for the purpose) and of the toxic action (at this temperature) of 

 the alcohol and organic acids present. Subsequently the name 



