FERMENTATION WITH SPECIAL REFERENCE TO THE SUGAR HOUSE. 



malt contains enormous numbers of bacteria, amongst which are the lactic and 

 butyric acid organisms ; butyric acid is a virulent yeast poison, and its develop- 

 ment would injure the yeast ; these organisms cannot be killed by raising the 

 temperature as this would also destroy the action of the diastase. The butyric 

 acid bacteria arc, however, themselves susceptible to slight degrees of acidity ; 

 in order to destroy them without injuring the yeast the temperature is arranged 

 so that the lactic acid bacteria can develop ; the optimum temperature of the 

 lactic acid bacteria is from 47 C. to 50 C., that of the butyric acid organisms 

 about 40 C. The mash is hence kept at a temperature of about 50 C., 

 whereby the lactic acid bacteria thrive and the formation of lactic acid effec- 

 tually prevents the development of the butyric acid organisms. When the 

 acid present reaches 1-0 to 1-1 per cent., the process is stopped by raising 

 the temperature to 70 C. ; the mash is re-cooled to 20 C. and pitched with 

 yeast, in the proportion of about 1 Ib. to 10 gallons; after about 14-16 hours 

 the yeast has so far developed as to be used in the main process, a portion being 

 kept for the next sour mash. 



This process left much to chance, and has been developed on other lines 

 although the object in view has always been the same. In the first place the 

 presence of lactic acid bacteria is adventitious, and although their presence is 

 very general, it not infrequently happened that the process miscarried by reason 

 of their absence ; to get over this difficulty the infection of the sour mash was 

 carried out by innoculation with pure cultures of lactic acid bacteria, and now 

 more recently a new process known as the hydrofluoric acid process has been 

 largely introduced. 



It was sought for a long time to find some substance that would be 

 antiseptic to the butyric acid bacteria and yet harmless to the development of 

 yeast, and after many bodies had been tried Effront, in 1890, introduced the 

 use of alkaline fluorides. The initial proposition was to add from 4 to 8 grms. 

 of hydrofluoric acid per hectolitre (say from ^V TTT^. per 100 gallons) of the 

 yeast mash which had been treated in the way described above, this quantity 

 being found sufficient to prevent the development of injurious organisms. 



Composition of Rum. Hum has now been defined as a spirit 

 distilled from fermented products of the sugar cane in a country where the 

 sugar cane is grown. This definition shuts out the use of the term for spirits 

 distilled from cane molasses imported to Europe or North America, and does 

 not differentiate between a juice and a molasses spirit ; originally the term 

 rum was applied to the former and tafia to the latter. 



Bum consists mainly of alcohol and water, the other bodies present being 

 caramel (in coloured rums), fatty acids, ethereal salts, aldehydes, higher 

 alcohols and essential oils ; the acids known to be present are formic, acetic, 

 butyric, and capric, both free and as ethereal salts. Miller 26 has given the 

 following analyses of Demerara rums : 



523 



