i6o CONCENTRATED FOOD-STUFFS 



(b) Enzyme. — A few grams of the beans are ground 

 to a meal and then introduced, a little at a time, 

 into a flask containing 200 to 300 c.c. of boiling 

 water. This process kills the enzyme, and prevents the 

 formation of HCN. The mixture is allowed to cool to 

 blood heat, maintained at that temperature for twelve 

 hours, and then tested for HCN as before. None should 

 be present. 



Cereals. 



156. Cereal Starches. 



The common cereals — wheat, barley, oats, maize, 

 rice, etc. — are ground finely and small portions of each 

 of the meals examined microscopically under a high 

 power. The nature of the starch grains in each case 

 should be noted and compared, and sketches made (see 

 P- 34). 



156. Examination of Wheat, 



{a) Preparation of Sample. — The wheat is reduced 

 to a fine flour which will pass through the 0-002 mm. 

 sieve. 



{b) Moisture and Ash. — Ten grams of the sample are 

 dried to constant weight in the steam-oven ; the residue 

 is then ignited to whiteness at a low red heat. 



{c) Wheat Proteins. 



Total Protein. — The nitrogen is estimated by Kjel- 

 dahl's method in about i gram of flour. Factor = 5-69. 



Crude Gluten. — The crude gluten or water-insoluble 

 protein of wheat is a mixture of at least two distinct 

 substances — the alkali-soluble gluten and the alcohol- 

 soluble gliadin. 



Ten grams of the flour are triturated in a mortar 

 with about 2 c.c. of water. The dough produced should 



