Chemical leaveners are important ingredients used in cookie and cracker products that cause expansion to occur by releasing carbon dioxide (CO2) gas into air cells established in the dough during mixing. The most common chemical leaveners used are ammonium bicarbonate or a combination of sodium bicarbonate with one or more acids. Ammonium bicarbonate, in the presence of moisture, requires only heat to react and provide expansion. Sodium bicarbonate (commonly called baking soda, or simply soda) requires an acid to produce CO2 gas. Some chemical leaveners will react during mixing, while others work during the baking process. All impact critical quality measures of your finished product including grain, texture, spread, height, surface appearance, color, and flavor.
- Grain: refers to the internal geometry of the product, including the shape, uniformity, size of the air cells, as well as the cell wall thickness. These air cells are established during mixing, and the grain is largely determined by their number and size. The larger the number and the smaller the size of air cells produced during mixing, the more fine and uniform the grain. The leaveners we use will expand within those air cells, also called nucleation sites. Using baking soda alone will react with the natural acidity of your other ingredients and begin to react in the mixer, contributing to an increase in nucleation sites. This process is enhanced by the addition of a fast acting acid such as MCP (Monocalcium phosphate) that will cause more of the soda to react early in the process. The use of slow acting leaveners, such as SAPP (sodium acid pyrophosphate) will only have some reaction during mixing, and delay the full reaction of the soda until heat is applied during the baking process. Ammonium bicarbonate, on the other hand, will not contribute significantly to gas production until baking. As you increase the quantity and type of leaveners that contribute to expansion during mixing, the grain will become more fine and uniform.
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