Leavening Agent

What is a Leavening Agent?

A leavening agent is an ingredient whose main function is the production of gas (air, steam, carbon dioxide or ammonia) in a dough or batter. One obvious function of leavening agents is the expansion of dough or batter to produce a volume increase which improves product texture and appearance.

Leavening agents are the third most important component in baking after flour and water. There are 4 major types of leavening agents:

1. Chemical leavening → Batter cakes
2. Biochemical leavening → Bread and buns
3. Mechanical leavening → Sponge cakes
4. Steam or thermal leavening → Production of steam from water in formula during baking

Leavening can also be produced using microorganisms (e.g. yeast and/or sourdough bacteria) or  chemical agents (baking powder, or ammonium bicarbonate). The resulting CO₂ gas, along with water vapor and entrapped air expand during baking, causing the dough or batter to rise.

Origin

The concept of leavening agents is as old as bread itself. Recorded evidence of leavened bread extends as far back as the ancient Egyptians and biblical times.

The first leavening agents involved the production of carbon dioxide gas from natural fermentation reactions carried out by wild yeasts and lactic acid bacteria. It was not until the 19th century that knowledge of chemicals first influenced the development of leavening agents, i.e. sodium bicarbonate and acid phosphates, that were later used in sweet baked goods.

Function

In addition to gas production and baked product volume increase, leavening agents can perform additional functions, such as:

• pH control (e.g. baking powder residual soda)
• Flavor enhancement (compounds produced during fermentation)
• Crust color improvement (slightly alkaline pH promotes Maillard browning reactions)

Commercial production

Leavening function can develop from many sources:

• Baker’s yeast → pure culture propagation, biomass growth and downstream processing
• Chemical leaveners (non-organic) → industrial production of food phosphates and bicarbonates
• Organic acids → industrial fermentation and downstream processing for acid concentration
• Steam → naturally produced during thermal processing thanks to water heating and vapor formation

Nutrition and health

Leavening agents do not perform a nutritional function in baked goods nor are they intended to enhance the nutritional value of the finished product. Some chemical leavening agents, like sodium bicarbonate, contribute to the total sodium content of a baked good.

Sodium is widely known for its contribution to blood pressure rise in humans. This is why most industrial bakeries are now searching for low-sodium baking powders that utilise alternative acids or bases, such as monocalcium phosphate and potassium bicarbonate, that are free of sodium.

Application

Types of leavening agents used in the bakery industry:

1. Chemical leavening
   • Bases and carbon-containing substances
     • Ammonium bicarbonate (NH₄HCO₃)
     • Ammonium carbonate ((NH₄)₂CO₃)
     • Baking soda (sodium bicarbonate, NaHCO₃)
     • Potassium bicarbonate (KHCO₃)
   • Acids
     • Sodium acid pyrophosphate (SAPP)
     • Sodium aluminum sulfate (SAS)
     • Sodium aluminum phosphate (SALP)
     • Organic acids (citric, tartaric)
     • Dicalcium phosphate dihydrate (DPD)
     • Dimagnesium phosphate
     • Glucono delta lactone (GDL)
     • Monocalcium phosphate (MCP)
2. Biochemical (biological) leavening
   • Baker’s yeast (Saccharomyces cerevisiae)
   • Sourdough
   • Pure lactic acid bacteria (LAB) cultures
   • Yeast-preferments (biga, poolish, sponge)
3. Mechanical leavening (air incorporation or entrapment as micro- and macroscopic gas bubbles)
   • Egg whites beating
   • Sugar / solid fat Mixing (creaming)
4. Steam leavening
   • Virtually all bakery products

Regulation

The following table summarizes the basic regulation status of some leavening agents:^1,2,3

References

1. National Archives, Code of Federal Regulations, Title 21 Chapter I Subchapter B Part 182 SUBSTANCES GENERALLY RECOGNIZED AS SAFE, https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-182, Accessed 23 October 2021.
2. National Archives, Code of Federal Regulations, Title 21 Chapter I Subchapter B Part 184 DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE, https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-184, Accessed 23 October 2021.
3. National Archives, Code of Federal Regulations, Title 21 Chapter I Subchapter B Part 172 FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION, https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-172, Accessed 23 October 2021.