276 AGRICULTURAL CHEMISTRY 



cent, is gliadin and 25 per cent, glutenin. Two samples 

 of wheat may contain the same amount of gluten, and 

 the flour from one produce good bread, while that from 

 the other is of very poor quality. The most valuable 

 wheats for bread-making purposes are those in which 80 

 to 85 per cent, of the protein is gluten, and the gluten is 

 composed of from 60 to 65 per cent, gliadin and 35 to 40 

 per cent, glutenin. A wheat may produce a good quality 

 of bread and at the same time contain a low per cent, of 

 protein, while, on the other hand, poor bread-making 

 qualities can be associated with a high per cent, of pro- 

 tein. Glutens which are usually considered the most 

 valuable for bread-making purposes are hard, elastic, and 

 of a light yellowish tinge. Poor gluten is dark in color, 

 has an uneven surface, possesses but little power to re- 

 coil, and is very sticky. 



Experiment 69. Gluten from wheat flour. To about 30 grams 

 of flour made from hard spring wheat, add sufficient water to form 

 a stiff dough and allow it to stand for half an hour, in order that 

 the physical properties of the gluten may develop. Place the dough 

 in a cloth and work it gently with the fingers, while a stream of 

 water is allowed to flow over it. Continue the washing until 

 the water that runs away is clear, which indicates that all starch 

 has been washed out of the dough. The washing may be completed 

 with the mass in the hand. Leave this gluten in water until 

 the gluten from flour made from soft winter wheat has been pre- 

 pared. Compare the two samples of gluten. 



Questions. (i) What is wheat gluten? (2) Describe hard 

 wheat gluten. (3) How does it differ from soft wheat gluten? 

 (4) How do the two moist glutens compare as to weight? (5) 

 Which gluten contains the larger amount of gliadin ? (6) Which 

 is the better quality of gluten for bread-making purposes? 



