20 LABORATORY MANUAL IN FIELD CROPS 



PRACTICUM NO. 16 

 Object. The Study of Flour and Flour Manufacture. 



Materials. Samples of whole wheat flour, bleached flour, 

 graham flour, and corn meal, microscope, No. 19 bolting cloth . 



Method. A very valuable addition to this exercise is a trip 

 to a near-by flour mill, if convenient. A written report of the 

 methods as observed by the student should be required. 



Examine all of the samples supplied and determine the fol- 

 lowing, tabulating the results in the notebooks : 



1. Granulations, under high-power microscope: round, 

 angular, square. 



2. Amount in a ten gram sample which will pass through 

 a No. 19 bolting cloth. 



3. Color, on plate glass under the disect. 



4. Percentage of gluten in a ten gram sample. Determine 

 by the wash method as follows : 



Weigh out a ten gram sample and place in an evaporating 

 dish ; mix into a stiff dough and keep adding more w^ater, 

 slowly working the mass until you have washed out all of the 

 starch, which is proved by the failure to get a blue-colored 

 reaction, when a weak solution of iodine is added to the wash 

 water. (Be careful that none of the sticky gluten is washed 

 away.) When the starch has been washed out, squeeze all 

 the water possible from the mass of gluten and weigh. Place 

 in the oven and when dry, weigh and determine the percentage 

 of dry gluten in the flour of the original sample. 



STUDIES 



1. What parts of the kernel make up the whole wheat flour? 



2. What relation does gluten have to bread making ? 



