Abstract

Objective

The goal of this project is to see how the varying the amount of baking powder in a muffin recipe affects the outcome of the final product.

Introduction

Warm muffins fresh from the oven are a great treat for a weekend breakfast. Making muffins (or other baked goods) can also be a fun way to learn some kitchen chemistry. It's interesting to see how the goopy batter gets tranformed in the oven into a perfect, miniature cake with a golden brown top. In this project you'll learn about what goes into a muffin to give it a nice, fluffy texture.

If you examine the texture of a muffin (or a biscuit, pancake, waffle, or slice of bread), you'll see that the basic structure is a random sort of meshwork that surrounds air spaces of various sizes. Without the air spaces, the end result would much more closely resemble a brick than bread. The air spaces are the result of bubbles of gas (mostly carbon dioxide) that are produced within the batter during the baking process. Ingredients that produce these bubbles are called leavening agents.

Muffins are an example of what bakers call a "quick bread" because, unlike a traditional bread dough, there is no yeast used in the recipe and no need to wait hours for the bread dough to rise. In a quick bread, the leavening agent is usually baking powder. Baking powder is a dry mixture that typically contains corn starch (as a filler and to keep the ingredients dry), sodium bicarbonate (a base, also known as 'baking soda'), sodium aluminum sulfate (an acid), and monocalcium phosphate (another acid). When baking powder dissolves in the liquid ingredients in your recipe, the basic component (sodium bicarbonate) can then react with the acidic components (sodium aluminum sulfate and monocalcium phosphate). One of the products of this chemical reaction is carbon dioxide gas, which provides the leavening for the baked product. As the batter is baked, the carbon dioxide produced by the baking powder makes bubbles in the batter. The bubbles are trapped by the surrounding structure of the batter, mainly supported by proteins in the flour and eggs.

You may notice that some baking powders (like the one described above) are called "double-acting." This is because one of the acidic components (sodium aluminum sulfate) reacts more slowly with the sodium bicarbonate. The reaction of sodium bicarbonate with the other acidic component of baking powder, monocalcium phosphate, is faster. The idea behind double-acting baking powder is that a greater proportion of the baking powder reaction (and hence carbon dioxide production) will happen during baking in the oven, rather than while you are still stirring the batter. In theory, this should mean more air spaces in the final baked product (i.e., higher rising, fluffier baked goods) with double-acting baking powder than with single-acting baking powder. (See the Variations section for a related experimental suggestion.)

If you get interested and learn more about baking, you'll find that there are several different kinds of leavening agents. For example, most regular bread doughs use yeast as the leavening agent. Yeast are single-celled organisms that consume some of the carbohydrates in bread dough and produce carbon dioxide gas as a byproduct. (To learn more about yeast, see the Science Buddies projects: Yeasty Beasties and An Aerobic Exercise: Yeast Metabolism with and without Aeration.) Some cakes (for example genoise-style cakes) get their spongy texture from the air spaces in whipped egg foam. The air bubbles expand as the air warms when the cake is baked. These types of cakes require a little more care with preparation technique in order not to lose the initial volume of the whipped egg foam when adding it to the other ingredients. It just goes to show you that a little science can even help you out in the kitchen.

When you're trying something new, is always best to start out simple, though, so muffins are a good way to go. If you compare several different muffin recipes, you will probably find that many of the ingredients are the same across the different recipes. However, you will probably also find that the amounts for the various ingredients differ slightly from one recipe to the next. The goal of this experiment is to find out what happens to the muffins when the amount of baking powder used in the recipe changes.

Terms, Concepts, and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• Quick breads (muffins, biscuits, pancakes, waffles)
• Leavening agents for quick breads
  • Baking soda (i.e., sodium bicarbonate)
  • Baking powder

Questions

• How do baking powder and baking soda work to leaven quick bread?
• What is the main difference between baking powder and baking soda?

Bibliography

• For information on baking powder and baking soda, try these references:
  • Wikipedia contributors, 2007. "Baking Powder," Wikipedia, The Free Encyclopedia [accessed August 25, 2007] http://en.wikipedia.org/w/index.php?title=Baking_powder&oldid=153617004.
  • Helmenstine, A.M., 2007. "What Is the Difference Between Baking Powder and Baking Soda?" About.com: Chemistry [accessed August 25, 2007] http://chemistry.about.com/cs/foodchemistry/f/blbaking.htm.
  • Cosmocel SA, date unknown. "Leavening Agents," Cosmocel SA, via D.W. Brooks website [accessed August 25, 2007] http://dwb.unl.edu/Teacher/NSF/C12/C12Links/www.cosmocel.com.mx/english/c-leave.htm.
• The recipe for cornmeal muffins is from:
  Beard, J., 1972. American Cookery Boston, MA: Little, Brown and Company, p. 795.
• A great reference for learning some of the food science of baking (as well as an excellent source of recipes!) is the following book:
  Braker, F., 2003. The Simple Art of Perfect Baking San Francisco, CA: Chronicle Books LLC.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

• Muffin pans
• Optional: paper muffin cups (for lining pan)
• Mixing bowl
• Measuring cups and spoons
• Muffin ingredients (enough for 4 half-batches, see recipe in Experimental Procedure below for more details):
  • Flour
  • Corn meal
  • Eggs
  • Sugar
  • Butter
  • Baking powder
• Oven
• Oven mitts
• Cooling rack
• Timer
• Kitchen scale is helpful, such as the Fast Weigh MS-500-BLK Digital Pocket Scale, 500 by 0.1 G, available from Amazon.com, but not absolutely necessary
• Camera is useful for photographing the results for your display board, but again, not absolutely necessary

Experimental Procedure

1. Do your background research so that you are familiar with the terms, concepts, and questions, above.
2. Use the muffin recipe below as a starting point (Beard, 1972), or pick your favorite muffin recipe and make a "half batch" of 6-8 muffins. Note: The recipe shown below will make 6-8 muffins. You can "halve" your own recipe by dividing the required amount of each ingredient by two. Be sure and note the ingredient amounts you use!
   1. 1/2 cup all-purpose flour
   2. 1/2 cup cornmeal
   3. 1/2 to 1 tablespoon sugar (to your taste)
   4. 2 teaspoons baking powder
   5. 1 egg, slightly beaten
   6. 1/2 cup milk
   7. 1/8 cup melted butter
   8. Mix all of the dry ingredients together in the mixing bowl. Make a well in the center and the beaten eggs, the milk, and the melted butter. Stir to a smooth batter. Fill well-buttered (or paper-lined) muffin pans about two-thirds full. Bake at 425°F for 15–20 minutes, or until nicely browned and baked through.
   9. Tip: do your best to start each muffin off with the same amount of batter. You can use a teaspoon to move small amounts of batter between the different cups in a pan to get the muffins equalized. On the other hand, you don't want spend too much time on this, because the baking powder starts working as soon as it touches liquid.
3. Remember to use oven mitts when putting the pans in the oven and when taking them out again.
4. Place the muffin pan on a cooling rack for a few minutes, and then tip the muffins out. Let them cool for a few more minutes before handling (or sampling!) them.
5. Make one half batch following the recipe above, and then three additional half batches, substituting the following amounts of baking powder:
   1. no baking powder,
   2. 1 teaspoon baking powder, and
   3. 3 (or even 4) teaspoons baking powder.
6. Remember to keep track of which batch is which!
7. Compare the four different half batches of muffins:
   1. Measure the height of each muffin in each batch and compute the average height for each batch. Note: if one muffin is much smaller than all the others, don't include it when calculating the average height.
   2. If you have a kitchen scale, you should also measure the weight of each muffin.
   3. More advanced students can also calculate the density of each muffin (see the Variations section, below).
   4. Slice some representative muffins from each batch so that you can compare the texture.
   5. Although it is definitely not the case for most chemistry experiments, for this one it's OK to do a taste test!
   6. Tip: for obvious reasons, it's important to do the size and weight measurements before the taste test!

Variations

• More advanced students can use height and diameter measurements to calculate the approximate volume of each muffin, and then use the measured mass of each muffin to calculate the density. Density is equal to the weight (in grams) divided by the volume (in cubic centimeters).
• Does double-acting baking powder (e.g. Clabber Girl® and Davis® baking powders) produce fluffier muffins than single-acting baking powder (e.g. Rumford® baking powder). Design an experiment to find out!
• From your background research on leavening agents, can you figure out a way to substitute baking soda for baking powder in your muffin recipe, without ending up with an unpleasant alkaline taste? Design an experiment to find out.
• Pick a different ingredient from the muffin recipe. Do research to understand the function of the ingredient in the recipe, and then predict what will happen when you change the proportion of that ingredient in the recipe. Design an experiment to test your prediction.
• Try modifying a bread recipe instead of a muffin recipe. For example, you could experiment to find out what happens if you reduce the amount of yeast used in the dough.
• For a related experiment, see the Science Buddies project Chemistry of Baking Ingredients 2: Can Baking Soda Substitute for Baking Powder in a Recipe?

• For more science project ideas in this area of science, see Cooking & Food Science Project Ideas.

Credits

Andrew Olson, Ph.D., Science Buddies