What is a “leavening agent”?
To put it simply, leavening agents are ingredients in baking that release gas inside batters and doughs. This makes whatever you are baking spongy in texture because the air created by the leavening agent gets trapped and cooked inside the batter/dough.There are three different types of leavening agents: biological (like yeast, buttermilk, kefir and yogurt), chemical (like baking powder and baking soda) and vaporous/physical (like air or steam). Below are examples of the differences in method between these 3 types of leavening agents.
How do these “leavening agents” work?
How these leavening agents work depends on the category they fall in.
For biological leaveners, there is a biological element that eats up sugar in your dough or batter (usually dough because of how long this process takes. The thinner batters cannot withstand the lengthy process that doughs can (because of their stronger “gluten matrix”) and the gas is released before enough is created). This biological element takes in sugars and releases carbon dioxide (CO2) and alcohol. This process is also used in fermenting beer (which is why beer is bubbly).
For chemical leaveners, a chemical reaction is needed to produce the gas. To produce the chemical reaction that produces the bubbles, you need two kinds of chemical leavening agents to react with each other and some form of liquid or heat for the reaction to happen in. The liquid can be one of the leavening agents or something else like water. The two different types of chemical leavening agents are alkaline/basic (there is a difference. Basic chemical leaveners react with or neutralize acids and alkali are water soluble versions of basic chemical leaveners.) and acidic. (You need one of each to produce a chemical reaction). The difference lies in the pH amount. To start from the beginning, pH is measured by the amount of hydrogen ions (hydrogen nuclei that have been separated from their electrons. These ions have a positive charge) in “a water-based solution”1.The term “pH” stands for “power of Hydrogen”. The pH level determines the acidity level what you are measuring. A pH level of zero is completely acidic, seven is neutral and fourteen is completely alkaline or basic. Alkaline and acidic things either neutralize or effervesce (create bubbles when combined in liquid) each other. One way to test pH levels is to use litmus paper. Litmus paper (a chemical indicator, which is used to test pH levels) is filter paper (like the paper that is used to filter coffee) that is coated with blue or red lichen dye (dye made from soaking lichen plant in water and ammonia), which react with what you are testing. The blue paper turns red if what you are testing is acidic, and the red paper turns blue if what you are testing is alkaline.
For vaporous/physical leaveners, whipping is the key. Air leavens batters/doughs when you whip sugar and some form of solid fat (like butter) together. Beating egg whites or cream works as well. All create air pockets that get cooked into batters and doughs. Steam works when moisture inside a dough or batter evaporates during cooking, giving off steam that gets trapped inside the dough or batter, creating air pockets.
All three methods have different ways of accomplishing the same end result: airier baked goods by way of air pockets. Although not all air pockets are the same, they all affect our food’s texture and density.
History of Leavening Agents
It is believed that the first leavening agents were used by the egyptians. They used airborne yeast in the form of breadmash. Airborne yeast was the most common leavener until the late 1700’s. The first chemical leavener was an alkali (pearl ash) created by native americans, who called it “soda ash”. They shared it with the colonial chefs, then it gained popularity in the colonial era. During the 1830s a new chemical leavener called “potash” was introduced, then Charles Fleischman created compressed yeast in 1868, which increased bread production rates. Then came, baking ammonia (baking powder’s foregoer. They have been interchanged (for a more crumble-like crust) because they function similarly) and sodium acid pyrophosphate (acidic chemical leavening agent), followed by baking soda and baking powder in the 1900’s
Baking Soda vs Baking Powder… what’s the difference?
Because of the name similarity, it may be thought that they are interchangeable or directly substitutable, but this is not the case. Again, the difference lies in the pH levels. Baking soda is usually used in baking with other acidic ingredients like vinegar and even honey because it is alkaline, while baking powder is used with neutral ingredients such as milk because it is a dry mixture of acid and alkali, lying just shy on the acidic side of neutral. You can substitute baking powder with baking soda and an acidic ingredient like lemon juice or yogurt, but just doing a direct swap can lead to denser, harder baked goods because there is no acidic element with the baking powder to cause the reaction and bubbles.
How is Density Calculated?
Density can be calculated by dividing mass by volume (density is an object’s mass per volume). Mass is sometimes interchanged with weight, but they are not the same. Mass is how much of something there is (usually measured compared to an object with a known mass) and weight is the measurement of gravity’s pull on an object (usually measured with a scale). You can divide weight in kilograms by 9.8 newtons (the force of earth’s gravity) to be technical, but for this experiment since both sets of biscuits are being made on the earth, weight can be used instead of mass.
Why Does Density Matter?
Have you ever bitten into a hard, slightly chewy biscuit? It’s not a pleasant experience, especially compared to the ideal crispy, light, butter glazed biscuits we imagine. But what causes this difference? Well, density plays a big role here. The first biscuit described had a more dense texture because of how close together the molecules are. Density is, in short, how much of something there is in that thing, or how packed together the molecules are. Dense baked goods can be caused by many things, like old baking powder (dough won’t rise right) and pudding. Some people even intentionally put pudding into their cake mixes to increase the density.
1 Helmenstine, Ph.D. Anne Marie. “Know the Definition of PH in Chemistry.” ThoughtCo, 31 Aug. 2017, www.thoughtco.com/definition-of-ph-in-chemistry-604605.