THE MICROBIOLOGY OF ALCOHOL PRODUCTS 535 



The malt used in saccharification may be made, in a manner similar to that 

 described for brewing, from barley, oats, rye or maize. As the object in this case is to 

 cause complete conversion of the starch with as little malt as possible, the malt 

 should have the maximum diastatic power. For this reason, germination should be 

 carried further than for brewing and the malt used green. Drying the malt de- 

 stroys half its diastase. 



The conversion may also be accomplished by boiling one part of grain in four 

 parts of water with hydrochloric or sulphuric acid. With the former acid, 10 per 

 cent of the weight of the grain is used and 5 per cent with the latter. The con- 

 version requires from eight to twelve hours' boiling. The starch is first converted 

 into dextrins and then into glucose. If the boiling is too prolonged some of the glucose 

 may be lost by conversion into caramel. The amount of acid and the time of boil- 

 ing may be much reduced by operating under 2 to 3 kg. pressure. In this case 200 

 liters of water are heated with 100 kg. of grain and 4 kg. of acid. Conversion occurs 

 in from 40 to 60 minutes. 



The power of certain molds, especially mucors, to convert starch into 

 sugar has been utilized. Mucor rouxii found in Chinese yeast, Mucor 

 oryzcB in Ragi, and related forms have been used for this purpose. This 

 is known as the Amylo Process. The grain is first soaked for a few 

 hours, then heated with twice its weight of water under a pressure of 

 three and a half to four atmospheres until soft and the starch rendered 

 soluble. The liquefaction of the starch is facilitated by sUghtly acidu- 

 lating the water with hydrochloric acid. The mixture is then cooled 

 to 38° and inoculated with a pure culture of the Mucor. A current of 

 filtered air is then passed through the mass for twenty-four hours, by 

 which time the mycelium has permeated the mass. The temperature 

 is then reduced to 33°, pure yeast added and aeration continued for 

 twenty-four hours longer to promote the multiplication of the yeast. 

 Conversion of the starch and fermentation of the sugar then continue 

 together. The mucor is capable of fermenting the sugar and producing 

 alcohol, but the yeast acts more rapidly. 



The malting process is the most commonly employed. The acid process de- 

 stroys a greater part of the value of the residues of distillation and the amylo process, 

 requiring costly special equipment and large expenditures for fuel, has not come 

 into general use. 



The starchy substances used being usually neutral- or of low acidity 

 the sugar solutions produced would be very liable to bacterial invasion 

 unless means of prevention were used. 



In the amylo process, the sterilization of the solutions and the use of 

 pure cultures accomplish this end. In the acid process, the minute 



