The chemistry of baking cookies

Although we generally don’t pay attention to it, something as simple as making cookies involves the use of different chemical elements, and different chemical processes and reactions take place. In many cases, more delicious recipes can be made by keeping some basic chemistry concepts in mind.

Common Chemical Elements in Cookie Ingredients

To prepare the chocolate chip cookies, we will need the following ingredients.

• 2 cups flour
• 2 eggs
• 1 cup chocolate chips
• 1 cup of sugar
• 1 cup of butter
• 1 teaspoon of baking powder
• 1 pinch of salt

In this list, the following chemical and biochemical compounds are included:

• Sucrose: it is common or table sugar. It is a disaccharide of glucose and fructose and its chemical formula is C ₁₂ H ₂₂ O ₁₁ . It is used to sweeten foods and is obtained mainly from sugar cane and sugar beets. It has the shape of small transparent crystals that, when reflecting light, give it a white color.
• Fats: they belong to the group of lipids and constitute an important part of the diet. They are found in butter, margarine, cream, oil, and other everyday products. At room temperature they can be solid or liquid. Furthermore, fats are insoluble in water.
• Proteins: they are essential for the growth and development of the organism, since they form the tissues and other body components. They are mainly present in eggs, dairy products and other products of animal origin. They are formed by chains of amino acids, compounds that contain carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sulfur (S) and phosphorus (P).
• Base: sodium bicarbonate (NaHCO ₃ ) present in baking powder, is a substance characterized by its high degree of alkalinity. Bases have a pH greater than 7 and neutralize acids. Sodium bicarbonate, when in contact with an acid, releases carbon dioxide and water, and produces effervescence. For this reason, it is used together with other acidic compounds to make baking powder, which works as a leavening agent (leavening agent) in different bakery products.
• Salts: are the result of a chemical reaction between a base and an acid. Common or table salt is sodium chloride (NaCl). It is generally obtained from seawater, and also from mining extraction or from some vegetables. It provides the typical salty flavor and also works as a preservative. In addition, it has a wide industrial use, both for the production of cosmetics and chemicals and in the preparation of pickles.
• Gluten: it is present in the flours of wheat, barley, rye and their derivatives. Although it is not essential for the body, it is a basic product in the human diet.
• Alkaloids: dark chocolate made from cocoa includes theobromine (C ₇ H ₈ N ₄ O ₂ ), an alkaloid from the group of methyl-xanthines, to which caffeine also belongs. Theobramine imparts the bitter taste to chocolate and is soluble in water.

Preparation of the chocolate chip cookies

• In a bowl, mix the butter with the sugar well.
• Then add the eggs and continue beating. Once integrated, add the flour previously sifted with the baking powder and mix until a homogeneous mass is obtained.
  Add the chocolate chips and mix them into the batter with a spoon, spatula, or your hands. Let the dough rest in the refrigerator for 20 minutes. Then, remove it and knead it again for 3 minutes. In this way it will acquire greater consistency.
• Preheat the oven to 180ºC.
• Shape the cookies and place them on the baking tray, leaving some spaces between them. Bake the chocolate chip cookies for 20 minutes.

What happens during the baking process

When the mixture is introduced into the oven, that is, when it is exposed to a change in temperature, some chemical reactions begin to take place. One of them occurs with sodium bicarbonate. This decomposes producing water and carbon dioxide. Carbon dioxide and water vapor form air bubbles that produce the leavening effect in the cookies. Not only do they swell, but they also prevent the cookies from coming out too dense or hard.

The salt slows down the breakdown of the baking soda, so the bubbles don’t get too big. The heat acts on butter, egg yolk and flour, and modifies their molecules.

The gluten in the flour creates a polymer mesh that reacts with the albumin protein in the egg white and the emulsifier lecithin in the yolk. In this way, the consistency of the dough is maintained.

Heat also splits sucrose into the simple sugars glucose and fructose. This gives each cookie its characteristic light brown color.

When you take the cookies out of the oven, the gases from the hot water in the cookies contract. But the chemical changes that occur during baking allow the cookies to keep their shape.
If they are not consumed immediately, other chemical processes continue to take place in which other factors may intervene. For example, the humidity of the environment can soften the cookies. Conversely, if the air is very dry, the cookies can harden.

How to apply chemistry to prepare the best recipes

Some basic chemistry concepts and the chemical properties and qualities of ingredients can help us make more delicious cookies. For this, it is important to take into account the following tips:

• If the eggs and butter are at room temperature they will mix more evenly. Thus, the cookie dough will already be at room temperature when they are placed in the oven, and their cooking will be favored.
• The type of shortening used will influence the texture, flavor, and color of the cookies. The use of butter is advised because other fats have different melting points.
• It is important to preheat the oven to 180°C because if the temperature is too low, the dough may spread out instead of hardening. This will not only influence the thickness of the cookie and its texture, but also the way it browns.
• In order for the cookies to brown evenly, it is important that they are the same size and thickness.
• It is important to mix the flour well with the baking powder and salt. It can even be sieved so that the ingredients are distributed evenly.
• After removing the cookies from the oven, allow them to cool. As moisture or dry air can change their texture and consistency, once cool, store them in a plastic container or airtight jar to keep them fresh.

Bibliography

• Chang, P. (2017, March 8). Chocolate chip cookies . Free recipes. Available at: https://www.recetasgratis.net/receta-de-galletas-con-chispas-de-chocolate-caseras-35926.html
• Córdova Frunz, JL Chemistry and cooking. (2008). Mexico. Economic Culture Fund of Spain.
• Mans, C. Chemistry in the Kitchen: A Quick Dive . (2018). Spain. Tibidabo Editions.