FERMENTATION 573 



In consequence of an abortive prosecution for selling Demerara rum as 

 Jamaica rum, Harrison 30 examined the ethereal salt content of Demerara 

 rums, finding a variation from 23-7 to 141-6, with a mean of 64-7 parts per 

 100,000 ; pot still rums contained on an average 69*9, and continuous still 

 rums 44-9 parts per 100,000 of alcohol. 



In Jamaica rums, classed as " common clean," Cousins 31 found 200-300, 

 in high-class ordinary rums 300-400, and in the best flavoured noo and up- 

 wards parts of ethereal salts per 100,000 of alcohol. 



The Flavour of Rum. It is generally held that the peculiar fruity flavour 

 of rum is due to the presence of ethyl ethers, particularly the butyrate and 

 caprylate. It has been shown by Cousins that these ethers, particularly 

 the latter, are present in very minute quantity, and that the ether predomin- 

 antly present is the acetate. Compared with the other ethers the acetate 

 and butyrate, particularly the former, are volatile, and these serve as a 

 means whereby the heavier ethers are conveyed to the organ of smell. 

 According to the same writer the accentuation of the flavour on dilution is 

 due to the presence of water decreasing the volatility of the acetate, thereby 

 masking its somewhat pungent yet pleasant smell. These remarks apply 

 exclusively to Jamaica rums, and not to Demerara rums of less ether content ; 

 in these Harrison 30 claims that the peculiarities are in some part due to the 

 caramel compounds used in colouring. 



In addition there is present in Jamaica rum a peculiar and diagnostic 

 substance, the presence of which was first demonstrated by Greg, who isolated 

 the substance by means of petroleum ether from dunder and from spirit. 

 He likens the flavour of this body to that emitted by new leather. This 

 body has also been isolated by Micko 28 by means of fractional distillation. 

 He states that it is neither an aldehyde nor a ketone, but has the properties of 

 an ethereal oil, though it may be allied to the terpenes. 



The sharp, unpleasant taste of newly distilled rum may be due to fatty 

 acids, which in the process of ageing react with the alcohol, forming ethereal 

 salts, an equilibrium between fatty acid, alcohol, ethereal salt and water 

 being finally formed. The agents contributing to the causes of the flavour 

 of rum are very complex. Greg, who was the first to study the matter, 

 succeeded in isolating a yeast that in its fermentation produced a specific 

 flavour. On the other hand, Allan 25 attributed the flavour of Jamaica rums 

 to the presence of fission yeasts and of butyric acid bacteria, of which he 

 isolated one, and of Bacillus mesentericus, to which he attributed the presence 

 of higher alcohols, especially butyl alcohol. Allan's work refers to Jamaica 

 rums, in the preparation of which bacterial action is prominent in the " muck 

 hole " (v. supra), but in the quick process followed in Demerara bacterial 

 action is prevented as far as possible by the use of bactericides. 



Ashby, 32 also working in Jamaica, was inclined to lay less stress on 

 bacterial action and more on the type of fermentation, observing that a 

 slow fermentation with a top fission yeast accentuated the production of 

 ethers and of a flavoured rum. 



Very recent experiments by Kayser 33 indicate marked differences in the 

 composition, and hence the flavour, of rum following on the scheme of 

 fermentation. With a spontaneous uncontrolled fermentation he found 

 high ethers, higher volatile acids, and low higher alcohols. With sterilized 

 material and pure fission yeasts, the ethers and volatile acids decreased, 

 the higher alcohols increasing. Spontaneous fermentation in the presence 



