The quality of cakes, flour tortillas, muffins, donuts, cookies, pizza and biscuits can be greatly impacted using the correct leavening system. Leavening delivers optimum or target volume, spread, texture and eating quality. The primary functional mechanism of the leavening system is to produce leavening gas at the appropriate time and quantity during the production process. Depending on the leavening system selected, the gas could be carbon dioxide (CO2), ammonia and/or water vapor. The leavening system can also affect color and flavor of the baked product. Additionally, the leavening system chosen is influenced by the baker’s process conditions, mixing, floor time and baking.
Breaking down the agents
The baker’s most common leavening gas source has been sodium bicarbonate, also known as baking soda or just soda. It is slightly alkaline, having a pH above 7.0. When added to a dough or batter, the acid in the flour reacts with the baking soda to release carbon dioxide gas. The more gas produced, the more leavening or aeration in the product.
For cookie formulations, baking soda could be the only leavening component. It is common to use more sodium bicarbonate than is necessary to neutralize the acid in the flour, and the resulting cookie has a slightly alkaline pH (above 7.0). When the cookie is slightly alkaline, the texture is more delicate due to greater leavening and resistance to gluten development. An alkaline pH also facilitates non-enzymatic browning, thus contributing to color and flavor development in the cookies.
The other component of the leavening system is the reacting component that controls the timing and rate of release of the leavening gas. These components are generally known as leavening acids or leavening salts. A common leavening acid used is cream of tartar, or potassium bitartrate. This is used most often in cookies and angel food cakes. In cookies, the cream of tartar reacts with the baking soda to release the leavening gas. In an angel food cake, the purpose is two-fold. First, it reacts with bicarbonate present in the formula to evolve gas; second, it increases the acidity of the egg whites, which are slightly alkaline. The increased acidity enhances the egg whites’ whipping ability, making it possible to incorporate more air into the batter, which will then become a foam. The leavening occurs in the oven through the expansion of the air trapped in the batter during mixing as well as the expansion of gas released from the leavening system.
Other leavening acids and acid salts can be used in leavening systems, including monocalcium phosphate (MCP), anhydrous monocalcium phosphate (AMCP), sodium acid pyrophosphate (SAPP), calcium pyrophosphate (CAPP), sodium aluminum phosphate (SALP), sodium aluminum sulfate (SAS), dicalcium phosphate dihydrate (DCPD), glucono-delta-lactone (GDL) and fumaric acid, plus encapsulated components and proprietary blends. The baker’s selection is based upon desired final product characteristics as well as the process conditions.
Choosing the right agent
There are three stages in the bakery production process where the reaction of the leavening system is important to deliver target product quality. The first is mixing. While the dough or batter is being mixed, it is important to generate sufficient incorporation of air. When this is insufficient, the dough or batter will not have enough air-cell nucleation sites for the development of a uniform grain structure. The resulting product can have a non-uniform grain, and this will risk blistering and tunneling problems in cakes and a tougher texture in cookies. Early leavening also contributes to early expansion during the baking process, helping to deliver sufficient volume.
Floor time is the second part of the production process important to leavening selection. The time between final mixing and dividing or depositing is critical in all baked goods to ensure that sufficient leavening power is retained to deliver expansion during baking. Expansion during holding can also lead to viscosity development and coalescence of air cells to form larger cells that are buoyant and easily lost during baking.
Baking is the third step that has an impact on the leavening agent decision. The baker needs sufficient gas produced during the baking stage to gain proper product volume. Proper volume also is generally related to attaining desired eating quality.
Depending upon the product, the type of baking powder or leavening system can change to achieve certain goals. Many baking powders and leavening systems include monocalcium phosphate, monohydrate (MCP or MCPM) as a leavening acid. MCP reacts primarily during mixing and helps build batter viscosity and contributes to air-cell nucleation. MCP is known as a fast-acting leavening acid because about 60% of the reaction occurs within the first two to three minutes of mixing at room temperature.
All leavening acids have a characteristic dough rate of reaction (DRR) or rate of reaction (ROR), which is the percentage of potential CO2 produced at a given time and temperature. For example, if the DRR is reported at two minutes, then acids with a lower DRR would enable retention of a higher percentage of gas for later in the process, possibly as late as the final stage or baking, and little activity during mixing. The acids with a higher DRR would have a lower percentage of gas produced in the final stage, baking, and, instead, have more CO2 production during mixing and/or floor time. DRR at two minutes for common leavening acids are as follows: MCP, 60%; SAPP, 21 to 43%; CAPP, 25%; SALP, 20%; DCPD, 20%; and GDL, 30%.
Some leavening agents are also considered to be time-delayed; when you wait long enough, the majority of the reaction will occur without exposure to the heating process. SAPP and CAPP are generally time-delayed components. GDL is unique because it starts to react slowly and has a slow continuous reaction profile.
To understand the application of these concepts, consider cake-style muffins. To create a product with a flat top and relatively dense and uniform grain, a single-acting baking powder would do the trick. MCP and soda in the leavening system or baking powder — a preblended combination of leavening acid and bicarbonate — would achieve the necessary incorporation of air during mixing. A flat-top muffin does not need as much leavening during baking.
On the other hand, for a bell-top muffin with larger volume, a double-acting baking powder with MCP and SAPP achieves the desired leavening effect. In the oven, the MCP would provide only 40% of its reaction, and the SAPP would contribute more than 50% of its reaction, giving the product more volume.
Lastly, to make a muffin with a peaked or cracked top, a baker could use a double-acting leavening system or baking powder with MCP, SALP and DCPD. Because SALP is slower than SAPP, the product would have gas produced for a longer time in the oven. DCPD would kick in very late in the baking process when the batter reaches a temperature of greater than 130°F (54°C), which would likely cause cracking in the product because the crust would be setting before the leavening was completed.
In today’s baking industry, there is interest in making products that meet consumer demands for health, clean label, natural or organic characteristics.
Interest in clean label, label simplification and natural are all difficult to address. There is no definition for natural. Although organic acids derived from natural sources could be used, there are cautions that must be considered: Is the acid actually from a natural source, or is it simply nature-identical? If not from a natural source, the regulators may question the use of the term natural.
Additionally, when organic acids, such as citric, malic and fumaric, are used, the leavening process must also be altered. Generally, these organic acids are fast in rate of reaction. The majority of leavening gas is released during mixing. This may not provide the desired final product characteristics.
Clean label and label simplification are also not clearly defined; they are usually defined by manufacturers themselves, often by the marketing team. One simplification option is to designate the leavening system as “baking powder” with a parenthetical designation of the components.
Since baking powders have been known since the mid-1800s, this is an acceptable way for the consumer to understand why the components are present and to relate to them. A single-acting baking powder will also simplify the label. Only the bicarbonate source and single leavening acid need be listed on the label.
Aeration by protein or foam production can also offer a solution to clean-label leavening as in the case of angel food cake and Japanese sponge cake.
In cake production without a leavening system, such as Japanese sponge cake, the batter must be stiffer, and mixing time must be longer.
The Japanese cake relies upon whole eggs and sugar for leavening. This results in a batter with low specific gravity, which means that significant air is incorporated during mixing. The more air incorporated in the batter paired with the batter’s ability to hold the trapped air, the more the batter will expand in the oven. This works for foam-based cakes like angel and sponge cakes. Generally, these cakes have drier textures than traditional chiffon cakes. Formulations for cakes made in the US would need to be modified extensively to eliminate leavening systems.
Another area of focus for consumers is the trend for health-enabling initiatives like fortification and sodium reduction.
The 2010 Dietary Guidelines for Americans recommended a reduction in sodium in food. The average consumer takes in about 3,400 mg sodium per day vs. a target level of less than 2,300 mg per day. The baking industry contributes more than 35% of the sodium in the average American’s diet.
Baking powder manufacturers have developed no-sodium and low-sodium baking powders. SAPP is about 21% sodium, but some SALP products are only about 2% sodium. Calcium-based leavening acids, such as MCP or calcium acid pyrophosphate (CAPP), add no additional sodium to the system and can be used in place of other sodium-based leavening acids. Overall, the baker can achieve 25% sodium reduction or greater.
As to fortification, the use of the calcium-based leavening components provides the benefit of extra calcium in the diet. CAPP when used in place of SAPP provides about a 25% decrease in sodium while at the same time providing a source of calcium, CAPP is about 19% calcium, which in many applications allows a claim of “good” or “excellent” source of calcium.
Baking powders and leavening systems do not have to be mysterious. Bakers have been using them for many generations. While there will continue to be changes in consumer interests, regulations and adjustments by bakers, these ingredients will always have an important role to play in the baking industry.
Call it organic
The US Department of Agricullture’s National Organic Program defines what can be used for products to be sold or labeled as “100% organic,” “organic” or “made with organic (specified ingredients or food group(s)). Federal regulation 7 CFR 205 designates ingredients as nonsynthetic or synthetic.
Nonsynthetics allowed include GLD, sodium bicarbonate, tartaric acid and yeast. Synthetics allowed are ammonium bicarbonate, calcium phosphates, MCPM, AMCP, DCPD and SAPP. Potassium bicarbonate is not currently allowed in organic-labeled products.
Can you make your own baking powder?
It is certainly possible for the baker to make his or her own baking powder, and some bakeries do this. There are advantages and disadvantages to either buying finished baking powder or making it. Buying a finished baking powder limits the amount of ingredients to weigh and add on the production floor. When bakers make their own, they can tailor the ingredients to work best in their formula and process. Additionally, a baking powder can be skipped all together, and individual leavening components can be added or a complete mix or concentrate used.
When making baking powder or a tailored leavening system, it is important to remember the concept of neutralizing value — the amount of baking soda needed to neutralize 100 parts of the leavening acid.
Step one is determining the amount of bicarbonate needed. Then calculate the amount of each leavening acid required to make a balanced formulation. Neutralizing values for common leavening acids are as follows: MCP, 80; cream of tartar, 45; SAPP, 72; CAPP, 72; SALP, 100; SAS, 104; GDL, 45; DCPD, 33; and fumaric acid, 145.
In the case of SALP, the same weight of baking soda can be used as SALP with no problem because the amount of baking soda neutralized by 100 parts of SALP is 100. Other acids require adjustments. A formula can be designed to be intentionally unbalanced as required by the product’s final target pH, to deliver target flavor, texture and color. A good example is the alkaline pH for chocolate systems.
Bakers can formulate their own leavening systems to deliver a reduction in sodium by selecting leavening components that don’t contain any sodium. Keeping in mind the two primary categories of the leavening system, many approaches are possible. Instead of the sodium bicarbonate, which is approximately 27% sodium, potassium bicarbonate can be used. When potassium bicarbonate is used, the source of leavening gas must be increased by about 19% in order to deliver the same level of carbon dioxide gas.