268 MICRO-ORGANISMS AND FERMENTATION. 



Professor HANSEN is still more far-reaching than is generally 

 assumed. A result of this reform is already being discussed 

 in brewing circles, namely, the abandonment of open coolers 

 in all breweries where pure yeast is employed, as these freely 

 permit of the contamination of the wort with micro-organisms, 

 and especially with bacteria and the so-called ' wild ' yeasts. 

 It is therefore proposed to filter the hopped wort, or to 

 separate the suspended matter (cooler-deposits) by another 

 method, to saturate the wort with filtered air, and to cool 

 it by artificial means. But these are by no means all the 

 precautions which must be adopted in order to guard against 

 further infection of the wort in the fermenting-rooms and in 

 the lager-cellar. Only when these questions have been 

 solved perhaps by means of closed fermenting -vessels of a 

 suitable material, by the sterilisation of the fermenting and 

 storage vessels, by a more rational arrangement of the fer- 

 menting-rooms and lager-cellars, and by the ventilation of 

 these by means of filtered air, etc. only then will it be 

 possible amongst beer producers and consumers to enjoy to 

 the full the great advantages of having a beer of better quality 

 and keeping properties than the present beer advantages which 

 are a result of the employment of pure yeast. 



" The above statements concerning the importance of pure 

 cultivated yeast refer throughout to beer bottom-yeast only. 

 There could be no doubt even from the first that it would 

 also be possible to employ HANSEN'S method of pure yeast- 

 culture to top-fermentation yeast, and with the same result ; 

 this has since been proved experimentally by ALFRED 

 JOERGENSEN, and pure top-yeast has proved just as successful 

 in the brewery as pure bottom-yeast. The writer of these 

 lines is convinced that the introduction of pure cultivated 

 species of yeast into distilleries, and especially into pressed- 

 yeast factories, will give very advantageous results. In 

 distilleries other conditions being maintained the same 

 better fermentations and a greater yield of alcohol in com- 

 parison with the average now attained are to be expected, 

 whilst in pressed-yeast factories a better yield of yeast should 

 result from a successful selection of a pure cultivated species, 

 and possibly the employment of clear mashes will then be 



