The Bulletin. 27 



Tlie same chemical action takes ]^lace when bicarbonate of soda is 

 used in conjunction with cream of tartar or sour milk. 



So far as the quality of the bread is concerned, there is no method 

 that will approach the natural process. This means of leavening is 

 at a slight loss of the bread, as the carbon dioxide gas, which does the 

 work, comes from the decomposition of sugar and starch and, of 

 course, to that extent, which is very small, lessens the value of the 

 bread, but w^hat is lost in quantity is gained in quality. The yeast, 

 or natural process of leavening is slow and cannot be used when 

 quick raising is desired. 



CONSTITUENTS OF BAKING POWDERS. 



Two ingredients are essential in a baking powder: a carbonate 

 which contains the carbon dioxide gas, necessary to raising the 

 dough, and an acid or its equivalent, which in the presence of mois- 

 ture, liberates carbon dioxide from the carbonate. In addition to the 

 essential constituents, most baking powders contain a filler, consisting 

 of starch or flour, which is used simply to improve the keeping quality. 

 Some other substances, such as sulphate of lime, argolite and tremo- 

 lite are sometimes used as filler, but are considered highly undesira- 

 ble additions to food products. 



Sodium bicarbonate, also known as baking soda, is the principal 

 carbonate, in fact, practically the only one, used in making powders. 



There is' more diversity in the acid constituents employed, the 

 principal ones being tartaric acid, cream of tartar, acid phosphate 

 of lime and the alums. 



The residue, the character of which depends upon the acid fur- 

 nishing material left in the bread, is the main objection to the use 

 of baking powders, its amount and character determining, to a large 

 extent, the healthfulness of the particular powder. 



The efficiency of a baking powder as a leavening agent depends 

 on the amount of gas it sets free in the dough, and must be considered 

 apart from the wholesomeness of the residue it leaves. 



CLASSIFICATION OF BAKING POWDERS. 



Baking powders are classified according to the acid constituents 

 they contain, as follows : 



Tartrate Powders, in which the acid is tartaric acid in some form. 



Phosphate Powders, in which the acid is phosphoric acid as an 

 acid phosphate. 



Alum Powders, in which the acid is sulphuric acid, contained in 

 some form of an alum salt. 



Alum-phosphate Powders, in which the acids are both sulphuric 

 and phosphoric acid. 



