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THE CHEMISTRY OF BREAD-MAKING 



flour, it will now be in order to take up the subject of bread-making. As was 

 previously stated, three essentially different methods of leavening, or pro- 

 ducing lightness in the dough, are to be considered. 



I. Leavening the Dough by Aeration of a Mechanical Character. — There 

 are a number of ways in which this has been done. One of the earliest methods 

 was that of Dr. Dauglish, of England. Flour is placed in a hermetically closed 

 cylinder and exhausted of its air. Carbon dioxid is then allowed to enter, the 

 cylinder opened, the flour removed and immediately made into a dough by the 

 addition of soda-water (water charged to saturation with carbon dioxid, com- 

 monly called "plain soda")- The dough, while in the Hght and porous con- 

 dition due to the bubbles of carbon dioxid entangled by the gluten, is immedi- 

 ately baked into loaves. In this process there is nothing added except perhaps 

 a little salt for seasoning, and there is a minimum of change in the constituents 

 of the flour. The changes that do occur are caused by the heat of baking, 

 in which the starch in the interior of the loaf is gelatinized and that of the crust 

 is dextrinized. The carbon dioxid is inert and plays a purely mechanical part, 

 supplying the gas for distending the elastic bubbles of gluten, giving the quaUty 

 of lightness to the product. 



Another aeration process, somewhat similar to that described above, uses 

 oxygen gas instead of carbon dioxid. Neither of these methods is adapted to 

 use on a small scale. Bread has been successfully made in cold weather by 

 mixing the flour with snow crystals, which carry enough air into the dough to 

 give a moderate degree of aeration and consequent lightness. One of the 

 unusual methods of aeration or vesiculation which has been proposed is to mix 

 a small volume of strong alcohol with the dough, which is then thoroughly 

 kneaded and placed in a warm atmosphere. The volatiHty of the alcohol 

 causes it to take the form of vapor, which distends the gluten in the form of 

 bubbles. If quickly baked, this lightness is retained long enough to set the 

 gluten firmly, the subsequent heating driving off practically all the alcohol. 

 Still another method, one on which a patent has recently been granted, is found 

 in the use of hydrogen dioxid solution instead of plain water in making the 

 dough. This is particularly appHcable in bread for diabetics, the flour for 

 which contains an extraordinary proportion of gluten, and which, by the 

 ordinary leavening process, usually makes a tough bread. Hydrogen dioxid 

 solution of standard strength is capable, upon decomposition, such as occurs by 

 contact with organic matter and the heat of baking, of yielding ten times its 



