252 



" SELECTED" YEASTS AND GENERAL CON- 

 SIDERATIONS. 



By Percival H. Greg. 



In considering the question of the adaptability of the " selected 

 yeast" system to our Jamaica Still Houses, a system which has found 

 such favourable acceptance in other countries, we must first of all con- 

 sider what are the requirements of the manufacturer of rum and the 

 conditions under which he labours. I may say without fear of contra- 

 diction that wherever by previous systematic experiment and by a care- 

 ful study of the circumstances of the case, the right type or variety of 

 yeast has been found, that the application of the system has been an un- 

 qualified success : and that the right type or variety of yeast exists and 

 may be found with the expenditure of a reasonable amount of energy is 

 proved by the ever increasing numbers of Breweries and Distilleries 

 working with selected yeast. 



It would however be a mistake to assume that this has been accom- 

 plished in a day, or that the principles when first enunciated by Emil 

 Christian Hansen were favourably received. Far from it ! The advo- 

 cates of the system had to encounter indifference, ridicule, and active 

 opposition. It would however be beyond the scope of this paper to enlarge 

 on these points, and would indeed be superfluous, since now that an English 

 translation of Hansen's " Untersuchungen aus der Praxis der Garung- 

 sindustrie" has been issued, tkose interested in the matter may drink in 

 knowledge from the fountain-head. It is sufficient to say that the first 

 success on a commercial scale was obtained by Hansen in the Old Carls- 

 berg Brewery in the year 1883 or 12 years ago, and that since then the 

 application of the system has not only grown steadily in the department 

 in which it was first introduced, but the principles upon which it is 

 based have found a successful application in many, other directions. It 

 seems natural therefore to question whether what has been so successful 

 elsewhere may not succeed in Jamaica. At the first glance it seems evi- 

 dent that there is one very great difference to be distinguished as regards 

 the application of selected yeasts between the manufacture of rum from 

 pure cane juice and the manufacture of beer or spirit from cereals. In 

 the case of beer, the " wash" or " wort" as it is called, i.e., that infusion 

 of malt and hops which on being fermented yields beer, is after a length- 

 ened period of boiling in the " wort" copper, and subsequent cooling on 

 the refrigerators or " coolers", brought into the fermenting tuns in a 

 more or less sterile condition. Of course experiments have shewn that 

 a certain amount of aereal contamination invariably takes place, but in 

 this case the germs are in a dessicated state, and it is pretty certain that 

 by far the greater number of them find such a strongly hopped medium 

 as ordinary beer- wort unsuitable for their growth in any considerable 

 measure, at any rate during the primary fermentation ; and of course 

 great care is taken to *' pitch" the wort, i.e. add yeast to it, immediately 

 that oxygen in sufficient quantity has been absorbed, and a favourable 

 temperature for fermentation has been reached. If then the wort be 

 pitched with a selected and suitable type of pure yeast in sufficient 

 quantity, there is very little to fear from the competition of foreign, 

 yeasts, i.e. yeasts other than the type intentionally employed. 



In well-conducted Distilleries the case is practically the same, though. 



