THE MANUFACTURE OF OTHER FERMENTED PRODUCTS. 463 



ducts being alcohol, succinic acid, volatile acids, mannit, amid-bodies, 

 carbon dioxide, hydrogen, methane and various aromatic esters. 



Weiss has isolated 65 different species of bacteria from sauerkraut. 

 Most of these are probably indifferent or harmless, and some harmful. 

 When the process is successful the lactic bacteria multiply rapidly from 

 the first and quickly produce enough acidity to restrain growth of the 

 harmful, among the worst of which are the butyric bacteria. 



STARCH. Starch is prepared from potatoes, corn, wheat, flour and 

 other amylaceous substances. The present method of separation is by 

 chemical means. Formerly it was accomplished by a complex fermen- 

 tation. 



For the fermentation method the grain is soaked in water until soft, 

 then ground and made into a paste which is allowed to ferment sponta- 

 neously or started with a leaven taken from a previous fermentation. 

 Alcoholic, lactic and butyric microorganisms attack the sugar while 

 others attack the gluten and cellulose. The fermentation lasts from 

 twelve to twenty-five days according to the temperature and the resist- 

 ance of the raw materials. 



During fermentation lactic and butyric acid, hydrogen sulphide, 

 ammonia and carbon dioxide with traces of alcohol and acetic acid are 

 produced. The process is stopped as soon as gas ceases to be given 

 off and before putrid fermentation sets in. The starch which is set 

 free settles to the bottom and is separated by decantation, washing and 

 screening. 



The washed starch is then allowed to settle for three or four days in 

 water. The sediment that is formed consists of three layers, the top 

 consisting principally of gluten, the second of gluten and starch and the 

 bottom of comparatively pure starch. The layers are separated and the 

 starch extracted from the two upper layers by repeated washings on 

 inclined planes. The starch, owing to its higher specific gravity, remains 

 near the lower parts of these planes. 



SUGAR. In the manufacture of sugar, microorganisms have no useful 

 part but many forms may be injurious and cause serious losses. The 

 juices of beets and sugar cane and the saccharine liquids obtained by 

 presses or diffusion batteries form excellent media for the multiplication 

 of many Saccharomyces and bacteria. They are controlled by cleanliness, 

 rapidity of handling, and sterilization by heat. They are injurious by 

 destroying sugar and thereby diminishing the yield, by inverting a portion 



