THE MICROBIOLOGY OP ALCOHOL PRODUCTS 537 



starchy substances, each vat is started with a mother yeast. The tem- 

 perature should be kept below 30° by means of refrigeration, otherwise 

 alcohol wiU be lost by the multiplication of bacteria. 



By the use of pure yeast, the yield in alcohol is greater as no sugar is 

 wasted in the production of lactic acid. The cost, however, is greater 

 owing to the necessity of the use of more heat in sterilization. 



The fermentation of sugar-cane molasses for the production of 

 . arrack is brought about by the use of a mother yeast called tapej, 

 prepared from ragi or Java yeast. 



Tapej is made by mixing powdered ragi with boiled rice. In two 

 days the rice is reduced to a semi-fluid condition and contains bacteria, 

 molds and yeasts. The bacteria seem to have no part in the process but 

 when too numerous are injurious. The mold Mucor oryzcB converts the 

 rice starch into sugar and the yeast 5. vordemanni produces alcohol from 

 the sugar. The other molds present are more or less injurious. 



