562 FOODS AND FOOD ADULTERANTS. 



to treat flours of inferior quality by this aerating method, the author wishes specially 

 to carefully avoid giving the impression that it is the habit of those companies which 

 work Dauglish's method to make use of only the lower qualities of flour; he has 

 never had any reason whatever for supposing such to be the case. 



This method is in operation in all the larger cities of Great Britain, 

 bat I have no knowledge of its being used in this country. 



CHEMICAL AERATING AGENTS. 



The necessity of sometimes having bread preparations raised quickly 

 for immediate baking led to the use of chemical agents for this purpose. 

 In all of these the expansive gas is the same as where yeast is used, 

 but instead of its being derived from the constituents of the flour, it is 

 obtained by the decomposition of a carbonate which is introduced, to- 

 gether with an acid constituent to act upon it, directly into the flour. 

 When water is added to make the dough the chemicals are dissolved, 

 the reaction occurs, and the carbonic acid is set free, while the salt re- 

 sulting from the combination of the acid with the alkaline base of the 

 carbonate remains in the bread and is eaten with it. Many suppose, 

 and this idea is fostered by baking-powder manufacturers, that nothing 

 remains in the bread, that everything is driven off during the baking. 

 This is entirely erroneous, of course, and the residue necessarily left in 

 the bread by baking-chemicals constitutes an objection to their use, and 

 its amount and character determine to a large extent the healthful ness 

 of the combination used. The essential elements of such a combination 

 are, first, a carbonate or bicarbonate which contains the gas combined 

 with an alkaline base, and, second, an acid constituent capable of unit- 

 ing with the base in the carbonate and thus liberating the carbonic-acid 

 gas. For the alkaline constituent bicarbonate of soda, " baking-soda," 

 is almost exclusively employed bicarbonate of ammonia much less. 

 For the acid constituent, however, there is great diversity in the agents 

 used. When the housewife mixes sour milk with baking-soda to " raise " 

 her griddle-cakes, she makes use of the free lactic acid of the former as 

 the acid constituent of her chemical aerating agent. When she uses 

 "cream of tartar" or acid tartrate of potassium with soda, she uses the 

 free tartaric acid of the former as an acid constituent, and this is the 

 same combination that is used in one class of the baking-powders sold 

 in the market. In fact, the entire line of such powders now sold is 

 practically the outcome of the old time operation of domestic chem- 

 istry, mixing "saleratus" and "cream of tartar" to aerate rolls, muffins, 

 pancakes, and such bread preparations, which were to be baked imme- 

 diately after mixing, and could not well wait for the slow operation of 

 yeast. They consist of an acid and an alkaline constituent in about the 

 proper proportions for combination, and in a dry state, together with 

 various proportions of a dry inert material, such as starch, added to 

 prevent action between the chemicals themselves, so that the prepara- 

 tion may be kept indefinitely. 



