255 



"but a small fraction of the total amount of liquor which passes through 

 the distillery. By far the greater bulk of the wash, as is well known, 

 consists of skimmings, molasses, and dunder. But it is precisely fur this 

 reason that I consider that systematically selected types of yeast might 

 be of such great service. In the first place, the " tempered" cane juice 

 will, on the generality of estates, have been steamed in the Syphons, and 

 though bearing in mind the resisting power of " spores" towards heat 

 and the fact that the skimmings contain a large amoimt of wax 

 which might enclose and protect some of the spores from the full effect 

 of the heat employed, and further bearing in mind that we have no rigid 

 experimental data to go upon in this particular instance, yet there seems 

 very little doubt that their subsequent growth and development will 

 have been retarded. As regards the molasses I have satisfied myself by 

 microscopical examination, that in the generality of cases the micro- 

 organisms present consist principally of Torula? which possess but a 

 slight fermentative power, and bacteria. These last might probably be 

 very much diminished in number if proper attention was paid to keep- 

 ing the sugar coolers and molasses hole clean. As regards the dunder 

 this must evidently be sterile when taken from the still, and when not 

 allowed to stand for any great length of time after having cooled down 

 is probably but little altered. 



It would seem then that as regards these liquids an}* particular culti- 

 vated yeast which we might desire to employ would not have to meet 

 with any extraordinary opposition from other germs. 



The subject naturally falls under two heads : First the effect of select- 

 ed types of yeast in imparling (a) an increased regularity to the progress 

 of the fermentations, (b) in giving the type of fermentation desired — 

 slow or fast, and (c) in obtaining a greater yield of alcohol from a given 

 weight of sugar ; second, the effect of selected types of yeast on the 

 flavour and aroma of the resulting products of fermentation, i.e., on the 

 ram. In a previous paper (The Jamaica Yeasts Bulletin for August) 

 I shewed in some tables that other things being equal, the whole character 

 and nature of the fermentation varied with the kind of yeast employed. 

 We may therefore dismiss questions a, b andc as not requiring discussion 

 but before doing so we must consider in how far the character of the fo- 

 mentation produced by a given type of yeast may be modified by circum- 

 stances. 



If is obvious, since yeast is a living organism, that unless the medium 

 in which it has to live is suitable to it, that it will not exercise 

 its functions completely, i e., will not assimilate or feed, will not grow- 

 and consequ( ntly will not ferment in the same degree which it could if 

 the conditions were entirely favorable. It must not therefore be hastily 

 assumed, that by using pure cultivations of selected types of yeast that 

 a mere mechanical regularity in the fermentation will be assured, 

 without any attention being paid by the Distiller to the nature and 

 composition of his washes. But it is evident that by working with a 

 known quantity, as we should do when working with a selected type 

 of yeast, which has been originally grown from one single cell, 

 that we are able to study the conditions or sets of conditions ' 

 which may be favorable or the reverse to the yeast in question in 

 advance, and thus we shall know what to aim at and what to < )id<'avour 

 to avoid in our practical operations. Whereas in working with a. 



