158 



Nathan) I examine the 40 fermenting vats which I had filled with one 

 and the same Must (fruit-juice) whether it was from berries or apples or 

 pears, and then afterwards infected each with a different kind or type of 

 yeast, the products of the fermentation differed from each other in such an 

 extraordinary manner that no one would have believed that he had to 

 do with one and the same material. While some types of wine yeast 

 gave for example the apple-must a very pronounced winey taste and 

 smell, others shewed themselves able to alter the material but little. 

 Some yeasts gave a very disagreeable after-taste to the must. Other 

 examples could be given shewing that the flavour of cream, butter, the 

 ripening of cheese, the aroma of tobacco, etc., are due to the activity of 

 special types or varieties of micro-organisms. Returning again to the 

 subject of the Jamaica yeasts, there is another point to be discussed. 

 In my last article I mentioned another fermentation which I obtained 

 with a Jamaica yeast which I called No. 4. I showed that there were 

 two apparent differences between the two yeasts, one the difference in 

 the resulting products of fermentation, i.e., the aroma, and the other 

 the time required by the two yeasts to ferment the same quantity of 

 the same mixture of molasses and dunder, i.e., No. 4 requiring 4-5 

 days, and No. 18, 10-14 days. Here we see then that the kind of yeast 

 employed is one of the deciding influences in what is a most important 

 point in the Still House, viz., the question of time. It may not be out 

 of place here to give a list of some of the Jamaica yeasts which I have 

 isolated and proved in fermentations in my Laboratory. 



Yeast 



Time of 



Attenuation 



Alcohol. 



No. 



Fermentation. 



of Wash. 



vol. per cent. 



No. 1 



3 days 



21-5 Brix. 



6.6 



No. 4 



8-4 days 



21-5 " 



7 6 



No. 5 



4-5 days 



21-5 " 



6.6 



No. 7 



4-5 days 



21-5.3 " 



6.6 



No. 8 



3 days 



21-4.8 " 



6.96 



No. 14 



4-5 days 



21-4.8 " 



6.90 



No. 17 



5-6 days 



21-4.6 " 



7.4 



No. 18 



12 days 



21-4° " 



7.2 



To translate Brix into Jamaica Saccharometer multiply by 1 . 33. 

 Thus 21-5 Brix=27.9 — 6.65. In considering these figures they 

 must be regarded in the light of a comparative rather than an absolute 

 test of the capabilities of the various yeasts. In this experiment 

 the yeasts were compared together under exactly the same conditions 

 and therefore the differences shewn can only be due to specific differen- 

 ces existing among the yeasts themselves. It is quite possible that the 

 differences might become still more marked under different conditions 

 such as for instance an increase in the initial density of the liquor. 

 Thus with No. 17 I have under favourable conditions obtained an at- 

 tenuation of 36 . 4-8=28 .4 degrees attenuation (Jamaica Saccharometer) 

 in from 5-6 days, but it does not necessarily follow that all the other 

 yeast in my list would under those conditions give corresponding re- 

 sults. As it is, however, the differences shown in time of fermentation, 

 amount of attenuation, and the quantity of alcohol produced, are worthy 

 of attention. As regards the attenuation it must be noted that the Brix 



