EXAMINATION OF CEREALS i6i 



leave the mortar with no trace of adhering. The 

 mixture is allowed to stand for an hour, placed in 

 a fine linen cloth, tied up, and kneaded gently in a 

 stream of water until the washings are clear and 

 consequently free from starch. This may be done by 

 hand or by means of an automatic stamping arrange- 

 ment. The crude gluten is removed from the cloth, 

 transferred to a weighed dish, dried slowly at iio°C., 

 and weighed. 



The elasticity, colour, and other physical character- 

 istics of the crude gluten are noted. 



Gliadin. — Four grams of the flour are extracted with 

 lOO c.c. of alcohol of sp. gr. 0-8724 (70 per cent, by 

 weight) in a tight-stoppered bottle. The liquid is 

 allowed to stand for three to four hours, with occasional 

 shaking, and is then filtered. Fifty c.c. of the filtrate 

 are evaporated to dryness in a Kjeldahl flask and the 

 nitrogen then estimated in the usual manner. Gliadin 

 = N X 5-67. 



The milling qualities of wheat and the baking qualities of flour 

 are largely determined by the nature, amount, and composition of 

 the crude gluten. In the average, wheat contains about 1 1 per 

 cent, crude gluten, but in the hard durum or macaroni wheats it 

 may reach 17 per cent, or more. 



From a good wheat, suitable for bread-making, the gluten 

 is elastic and light yellow in colour. Poor glutens from inferior 

 or damaged wheat are sticky and adhere to the cloth, are with 

 difficulty united to a single mass, and are much darker coloured 

 than that from good flour. These variations are partly due to 

 differences in the proportion of gliadin present in the crude gluten j 

 it is stated that the amount of gliadin profoundly aflects the baking 

 quality of wheat. 



Barley and Malt. 



157. Barley, 



{a) Barley is grown chiefly for the preparation of 



L 



