Development of Baking Powder

For more than three millennia, the method of baking bread did not change substantially; that is, until the 1830s when bakers began adding sodium bicarbonate (bicarbonate of soda) and sour milk to their dough. The lactic acid in the sour milk reacted with the sodium bicarbonate to produce carbon dioxide, which, trapped in the dough, resulted in the desired lightness of the baked bread. The introduction of sodium bicarbonate with an acid marked a significant advance in baking technique. But its applicability was limited since baking powder works better in cakes and biscuits than in breads. As a result, most bread makers continued to use sour dough.1

Adding sour milk to dough or batter presented a problem: the chemical reaction depended upon the degree of acidity in the sour milk which made the resulting rising unpredictable. In the 1840s the introduction of cream of tartar (potassium hydrogen tartrate), a by-product of wine fermentation, solved this problem. Cream of tartar greatly improved and regularized the baking process since the uniformity of both sodium bicarbonate and cream of tartar offered bakers better control of the leavening process, allowing for predictable results.

The mixing of sodium bicarbonate and cream of tartar marked the introduction of baking powder. The action of the two chemicals — initially marketed in twin envelopes — began as soon as they were added to the wet dough or batter. Bakers began buying both chemicals in bulk, but they had to be kept separate to prevent a premature acid-base reaction occurring. This required extra time in measuring. And there was an additional problem as cream of tartar was imported from France and Italy. The supply and price of cream of tartar was erratic depending on the grape harvest. These two factors — that the components of baking powder had to be kept separate and that the availability of cream of tartar was erratic — fueled the search for a more efficient and economical baking powder.

It was at this point that a German-educated, Harvard chemist named Eben Horsford suggested replacing the cream of tartar with calcium acid phosphate, which he knew as monocalcium phosphate. Horsford then developed a process to manufacture calcium acid phosphate, for which he received a patent on April 26, 1856.2 Earlier, Horsford and his partner, George Wilson, had established the Rumford Chemical Works for the manufacture of chemicals; soon the plant was producing calcium acid phosphate. In the early years of the factory the source for calcium was bones, which were treated with sulfuric acid. This resulted in a mixture of phosphoric acid, superphosphates, and calcium sulfate which was laboriously fractionated to yield calcium acid phosphate, which Horsford called "pulverulent (powdered) phosphoric acid."

The first packaged products from the Rumford Chemical Works were correctly proportioned supplies of calcium acid phosphate and sodium bicarbonate marketed as Horsford's Bread Preparation. While the introduction of calcium acid phosphate satisfied the supply problem presented by cream of tartar, the baker still had to mix two products to get a satisfactory leavening agent. Since it was the presence of water which began the reaction process, Horsford solved the problem by drying the ingredients sufficiently. To keep them dry, he added corn starch to the mixture as the vital third ingredient. Horsford had discovered that finely ground calcium acid phosphate and bicarbonate of soda could be mixed with finely divided corn starch to prevent a premature chemical reaction. Corn starch remains an essential feature of most baking powders.

The baking powder devised by Horsford first carried his name, only later becoming Rumford Baking Powder. As such it was marketed for decades and contained the same three ingredients — calcium acid phosphate, sodium bicarbonate, and corn starch — in the same proportions as in Horsford's day. The only significant change came in the source of the calcium acid phosphate; in the late 1880s, the introduction of calcium phosphate mining eliminated the need for beef bones.

1 For the history of baking powder, see the following: Anon., Eighty Years of Baking Powder History: 1859-1939, Rumford, RI, Rumford Chemical Works, 1939; Eben Norton Horsford, The Theory and Art of Bread-Making: A New Process Without the Use of Ferment (Cambridge, Mass: Welsh Bigelow & Co., 1861); Paul R. Jones, "Justus Von Leibig, Eben Horsford and the Development of the Baking Powder Industry," Ambix 40, Part 2 (1993): 65-74; Anon, "History of the Rumford Chemical Works," typed manuscript, dated April 15, 1947, in the East Providence Historical Society; Anon., "The Story of Baking Powder — The Story of Rumford, reprint from Oil-Power in East Providence Historical Society.

2 See the application for a patent in the East Providence Historical Society.


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