Chemical leavening in three acts

by Laurie Gorton
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Continuing our series on chemical leavening, let’s see its effects in three different areas…

Before the oven

Leavening acids jump into action during mixing, each type reacting with the bicarbonate at a different time and speed. Encapsulated styles, however, need the heat of the oven to initiate release.

Some acids act quickly to give nucleation that provides gas bubbles. These work best when doughs or batters don’t get much mixing that would otherwise provide aeration. Other acids are slower, explained Sharon Book, PhD, bakery technologist, ICL Food Specialties, St. Louis. They act during baking before set, when the gas can be trapped in the matrix to provide volume.

Dr. Book cited refrigerated dough as a product that requires precision in its leavening. “There is only one kind of slow-reacting SAPP that allows the dough to proof in the [refrigerated dough] can,” she said. “Often, an additional acid is added to provide leavening during baking to give adequate final product characteristics.”

Donuts are another example. Leavening must release gas quickly once the donut batter hits the hot oil, and SAPP is critical to this application. But other items need slower-acting or heat-released agents. “Pancake batter that will be in a restaurant refrigerator for a few hours creates a larger, better-quality cooked pancake if a heat-activated leavening like SALP is used,” said Robert Mason, senior scientist, applications lab, encapsulates and inclusions, SensoryEffects Ingredient Solutions, a division of Balchem, Bridgeton, MO. And muffins get their desirable cracked crust through DCPD’s late reaction.

Generation of gas bubbles increases the viscosity. Mr. Mason noted this is particularly valuable for thin batters made with MCP. “This helps the filling of pans and support of inclusions,” he said. “Faster SAPP leavening acids do this as well.”

Some leavening acids can strengthen gluten proteins, noted Nita Livvix, R&D director, Clabber Girl Corp., Terre Haute, IN. “Phosphates work in conjunction with gluten, especially calcium phosphate, to strengthen dough structure.”

Mr. Mason confirmed this effect. “A lot of what you’ll find in the scientific work relates to leavening acids containing calcium cations such as MCP and CAPP,” he said. “Calcium will cross-link with protein to generate a finer crumb structure.”

In finished products

Probably the most important aspect, after gas generation, is pH. The acid-base reaction opens the door for subtle influences on color and flavor, explained Paul Bright, innovation manager, AB Mauri North America, Chesterfield, MO, “Two key examples of this include darkening of chocolate cakes by use of sodium bicarbonate to increase pH and whitening of biscuits and development of desired flavor using MCP and SAPP to lower pH.”

To play the pH card, formulators will slightly unbalance the neutralizing equation to leave an excess of soda (alkaline and higher in pH) or leavening acid (acid and lower in pH). This affects crumb color, an important sensory parameter, Dr. Book noted. “A darker color can be achieved with a dark cocoa, or using a lighter cocoa and optimizing the acid-base balance to give a higher pH. With non-chocolate products, the color can also be due to the leavening system. A more alkaline pH will be slightly more yellow in tone, and acidic pHs tend to be brighter and more white,” she said.

Sodium bicarbonate promotes browning by speeding up the Maillard reaction between amino acids and reducing sugars, Ms. Livvix explained. “The solubility of the various leavening acids determines their relative effectiveness in lowering pH,” she said.

Interesting effects will occur, and Mr. Mason recalled a recent project: A customer’s banana bread was coming out dark brown, almost like gingerbread, instead of the slightly grayish crumb color normal for this item. “The formula’s pH was too high,” he explained. “Once the leavening system was properly balanced, the bread regained its normal appearance, but when we pushed the batter to the acid side, it looked more like pound cake.”

Siobhan Foley, technical sales manager, North America, Kudos Blends Ltd., Cleobury Mortimer, UK (distributed in the US by Brenntag North America, Reading, PA) reported research into how baking powders adjust the pH of the end product. The company sells a range of acidified baking powders in Europe. “Bakers who use these ingredients have found that it allows them to gain consistent products, reducing their waste and saving a lot of time in reformation,” she said.

She noted as well that altering parts of the leavening system can assist with taste. “When swapping from sodium bicarbonate to potassium bicarbonate, the soda taste gained from the presence of sodium bicarbonate is no longer there,” Ms. Foley said. “The product appears sweeter because the sugar isn’t being masked.”

The choice of one leavening system over another also makes a difference in the size, texture and symmetry of baked products. “Research has shown that not all leavening acids are the same in how they influence the size and textural characteristics of cakes,” Dr. Book said. Such results must be weighed against other product specs. For example, she noted that tests with CAPP showed the largest cake with the most cohesive texture, but it also yielded a browner crust.

Kim Powell, commercial development specialist, bakery, Innophos, Inc., Cranbury, NJ, elaborated about the influence of leavening ingredients on the final texture. “SAPPs will give a softer, moister texture, with more open cell structure while CAPP or SALP will add some resiliency and finer air cells,” she said. “Sodium aluminum phosphate (SALP) will give the most resilient, springy texture. MCP addition helps to create a fine air cell distribution while SAPP tends to give a more open structure. When finer cells are present, there is more surface area and less shadowing, creating a brighter appearance: whiter in a white product, more yellow in a yellow products. Larger air cells tend to impact the appearance to be grayer, less white.”

Symmetry of the finished product is a factor, too.  Mr. Bright explained, “A baker can produce muffins with flat, bell or peak tops just by changing the type of leavening acid used. Additionally, leavening acids can also affect the desired internal crumb structure — whether it be more open or coarse or more fine and uniform — of finished baked goods.”

On the shelf

And there’s a preservative angle as well. “Chemical leavening can adjust pH to maintain preservative function,” Ms. Foley said. “Preservatives perform better in a lower pH environment, and by adjusting your raising agents, you can optimize preservative function.”

Outright replacement is also possible. Ms. Livvix explained, “Some leavening acids have been shown to act as preservatives when used at levels above the amount needed to neutralize a gas source such as sodium bicarbonate.”

For refrigerated and frozen doughs and bakery mixes, chemical leavening influences shelf life in a different way — by not acting until the consumer or foodservice operator bakes them off. Encapsulated leavening ingredients effectively manage this delay and lengthen the shelf life of such products.

“The main reason for using encapsulated bicarbonates and leavening acids is to guarantee the leavening system’s primary function: aeration,” Mr. Mason said. “Typical shelf life for frozen doughs containing regular chemical leavening is three to four months, but encapsulation of the leaveners will give up to one year of shelf life.”

Storage time can affect leavening selection, too. In dry mixes, the acid and bicarbonate tend to react in the presence of residual moisture. “By using more stable leavening acids — that is, those with less potential for immediate reaction — the shelf life of a dry mix can be controlled,” Ms. Powell said. Coating and encapsulation answer this problem.

For fresh production, timing of the leavening reaction matters a great deal. Batters with long hold times need slower reactions so that lift will still happen during baking, Ms. Powell explained. SAPP generally can tolerate longer bench times, as well as SALP. For refrigerated batters and dough, very stable reactions are also needed and can be accomplished with slow SAPPs, SALP or DCPD — it won’t react at all until reaching baking temperatures.
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