UPON THE FLOUR OF WHEAT. 606 



bread than the flour of any other grain. If the gluten be washed out of 

 the flour, and put alone into the oven, it will swell up, become full of 

 pores, and assume a large size. The comparative baking qualities 

 of ditferent samples of flour may be judged of by the height to v/hich, in 

 similar vessels, the gluten of equal weights of flour is thus observed to riee. 



We have already seen that by heating in an oven, dry starch is gra- 

 dually changed into gum {British gum, p. 113), and into a species of 

 sugar — becoming completely soluble in water. Such a change is pro- 

 duced upon a portion of the starch of wheaten flour when it is baked in 

 the oven. Thus in 100 parts of the flour, and of the bread of the same 

 wheat, Vogel found respectively — 



Starch. Sugar. Gum. 



Flour ... 68 5 — 



Bread . . . 53i 3| 18 



So that a very considerable portion of gum had been produced at the ex- 

 pense of the starch. 



The yeast which is added to the dough in baking, acts in the same 

 way as when it is added to the sweet wort of the brewer. It induces a 

 fermentation by which the sugar of the flour is changed into carbonic 

 acid and alcohol. The carbonic acid is liberated in the form of minute 

 bubbles of gas throughout the whole substance of the dough and causes 

 it to rise, the alcohol is distilled off' in the oven. If too much water 

 have been added to the dough — or if it have not been sufficiently knead- 

 ed—or if the flour be too finely ground — or if the paste be not sufficiently 

 tenacious in its nature, these niinute bubbles will run into each otlier, 

 will form large air holes in the heart of tlie bread, and will give it that 

 open irregularly porous appearance so much disliked by the skilful 

 baker. Good bread should be full of small pores and uniformly light. 

 Such bread is produced by a strong flour ; that is, one which will rise well, 

 will retain its bulk, and will, bear the largest quantity of water. 



The quantity of water which wheaten flour retains when baked into 

 bread depends in some degree upon the (juality of the flour. In the 

 Acts of Parliament relating to the assize of bread, it is assumed that a 

 sack of flour (280 lbs.) will produce 80 quartern loaves, or 320 lbs. of 

 bread. According to this calculation the flour should take up and retain 

 when baked one-seventh of its weight of water. But the quantity of water 

 retained by the flour now in use is very much greater, and the profit to 

 the baker, therefore, very much more than this calculation supposes. 



This is shown by the quantity of water which is lost by wheaten 

 bread, whether of first or second quality, when it is dried by prolonging 

 heating, at a temperature not exceeding 220° F. The home-made 

 bread (white and brown) baked in my own house, and in two other 

 private houses in Durham, lost of water by drying in this v/ay — 



• The brown bread is made from the whole grain of the wheat as it comes from the 

 millstones— nothing being separated by sifling. 



