FERMENTATION 321 



tion. These ferments change the insoluble nitrogenous 

 and non- nitrogenous compounds to soluble forms, which 

 are utilized by the young plant as food. If a seed were 

 deprived of all of its soluble ferments, it would fail to 

 germinate. 



Experiment 74. Action of malt on starch. Crush in a mortar 

 twenty malted barley kernels, transfer to a test-tube, and add 

 15 cc. water. After twenty-four hours, filter off the solution, and 

 add it to a flask containing 2 grams of flour and 100 cc. water. 

 Place the flask in the desk for twenty-four hours ; then filter off 

 the solution and test a portion for starch with iodin, as in Experi- 

 ment 45. Test another portion for glucose with Fehling's so- 

 lution, as in Experiment 48. 



Questions. ( i ) What is malted barley ? ( 2 ) What did the water 

 extract from the barley contain? (3) What effect did this extract 

 have upon the flour? (4) What did the tests with iodin and Feh- 

 ling's solution show? (5) Would flour treated with water instead 

 of malt extract give the same result ? 



443. Ferments in Bread-flaking The yeast plant 

 employed in bread-making secretes a number of soluble 

 ferments which produce the desired chemical changes. 

 The diastase ferment changes the starch to soluble forms, 

 the alcoholic ferment produces alcohol and carbon dioxid 

 gas, which expand the dough and make the bread light, 

 and acid ferments produce acids, which combine with the 

 gluten proteids and modify their character. In short, 

 bread-making is simply a series of chemical changes in- 

 duced by soluble ferments. 



Experiment 75. Alcoholic fermentation. Weigh 10 grams 

 of flour into a flask, add 50 cc. water and a small piece of yeast 

 (one-tenth of a cake). Connect the flask by means of a delivery 

 tube with the Woulff bottle containing enough clear lime water to 



