Chemistry of Baking Ingredients 1: How Much Baking Powder Do Quick Breads Need?
AbstractIf you like to bake, this could be a good science project for you! Have you ever wondered about the purpose of each of the ingredients in your favorite recipes? For example, why is baking powder used in some muffin recipes? How does the baking powder affect how the muffins look, feel, and taste? In this food science project you will use a scientific method to find out!
To see how varying the amount of baking powder in a muffin recipe affects the outcome of the final product.
Andrew Olson, PhD, and Teisha Rowland, PhD, Science Buddies
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Warm muffins fresh from the oven, like the ones shown in Figure 1, below, 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 is interesting to see how the goopy batter gets transformed in the oven into a perfect, miniature cake with a golden brown top. In this science project you will learn about what goes into a muffin to give it a nice, fluffy texture.
Figure 1. Muffins are a tasty treat that normally have a nice, fluffy texture.
If you examine the texture of a muffin (or a biscuit, pancake, waffle, or slice of bread), you will see that the basic structure is a random sort of meshwork that surrounds air spaces of various sizes, as shown in Figure 2, below. What do you think the end result would look like without these air spaces? 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, and make dough and batter foam, are called leavening agents.
Figure 2. Muffins have air spaces inside of them, as shown in this muffin that has been cut in half. The air spaces are due to carbon dioxide gas produced by leavening agents during the baking process.
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 - when you use yeast in bread dough, you need to wait hours for the 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). (You do not need to know about the chemistry of acids and bases to do this science project, but if you would like to learn more about them, you can check out the Science Buddies resource on Acids, Bases, & the pH Scale.) When baking powder dissolves in the liquid ingredients in your recipe, the sodium bicarbonate (the basic component) can react with the sodium aluminum sulfate and monocalcium phosphate (the acidic components). 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.
Some baking powders are "double-acting" while others are "single-acting." This has to do with the exact ingredients that are in the baking powder and how they react with the sodium bicarbonate. Sodium aluminum sulfate reacts more slowly with the sodium bicarbonate, while the reaction of sodium bicarbonate with the other acidic component of baking powder, monocalcium phosphate, is faster. Double-acting baking powders contain both the slow- and fast- acting acidic components (sodium aluminum sulfate and monocalcium phosphate). Single-acting baking powders, on the other hand, only contain one of the acidic components. 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 Make It Your Own section for a related science project suggestion.)
If you get interested and learn more about baking, you will 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 are trying something new, it 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. In this science project you will find out what happens to the muffins when the amount of baking powder used in the recipe changes.
Terms and Concepts
- Carbon dioxide
- Leavening agents
- Quick breads (e.g., muffins, biscuits, pancakes, waffles)
- Baking powder
- Baking soda
- Chemical reactions
- How do baking powder and baking soda work to leaven quick bread?
- What is the main difference between baking powder and baking soda?
For information on baking powder and baking soda, try these references:
- Wikipedia contributors, 2007. "Baking Powder," Wikipedia, The Free Encyclopedia. Retrieved August 25, 2007 from 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. Retrieved August 25, 2007 from http://chemistry.about.com/cs/foodchemistry/f/blbaking.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.
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Materials and Equipment
- Muffin pan that holds 6 to 8 muffins
- Optional: Paper muffin cups, for lining pan
- Mixing bowl
- Measuring cups and spoons
- Muffin ingredients. Note: If you use the recipe in the
Procedure, these are the ingredients and amounts you will need, but if you use a different recipe you may need to change the ingredients and amounts needed:
- Flour, all-purpose (2 C)
- Corn meal (2 C)
- Sugar (2 Tbsp.)
- Baking powder (8 tsp.)
- Note: Either single action or double action baking powder can be used as long as you use the same type of baking powder across all batches.
- Eggs (4)
- Milk (2 C)
- Butter (1/2 C)
- Oven mitts
- Cooling rack
- Ruler, metric
- Optional: Kitchen scale is helpful, such as the Fast Weigh Digital Pocket Scale, 500 by 0.1 G , available from Amazon.com, but not absolutely necessary
- A camera is useful for photographing the results to put on Science Fair Project Display Boards, but again, this is not absolutely necessary.
- Lab notebook
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Chemistry of Baking Ingredients 1: How Much Baking Powder Do Quick Breads Need?
- Do your background research so that you are familiar with the terms, concepts, and questions, in the Background section.
- Use the muffin recipe in step 4, below, as a starting point (Beard, 1972), or pick your favorite muffin recipe. The recipe below will make 6-8 muffins. You should adjust any recipe you use so that it makes 6-8 muffins (this is often called a "half batch" and can usually be achieved by dividing the required amount of each ingredient by two). Be sure and note the ingredient amounts you use!
- Preheat the oven to 425° Fahrenheit (F).
Mix the following dry ingredients together in a mixing bowl, as shown in Figure 3, below:
- 1/2 cup (C) all-purpose flour
- 1/2 C cornmeal
- 1/2 tablespoon (Tbsp.) sugar
- 2 teaspoons (tsp.) baking powder
Figure 3. First mix the dry ingredients (flour, cornmeal, sugar, and baking powder) in the mixing bowl.
Make a well, or hole, in the center of your dry ingredients in the mixing bowl, as shown in Figure 4, below, and then mix in the following ingredients:
- 1 egg, slightly beaten, as shown in Figure 5, below
- 1/2 C milk
1/8 C (or 2 Tbsp.) melted butter
- Tip: Since you will be preparing multiple recipes, it may be helpful to melt a larger amount of butter in a bowl, as shown in Figure 6, below, and then measure out what you need from the bowl for each recipe. If the butter re-solidifies before you use it, be sure to melt it again before mixing it in with the other ingredients.
Figure 4. In the mixing bowl with the dry ingredients, make a hole, or well, as shown here, and then add in the wet ingredients there.
Figure 5. Slightly beat an egg, as shown here.
Figure 6. Prepare some melted butter and measure out what you need from it.
- Stir the mixture to a smooth batter, as shown in Figure 7, below.
Figure 7. Stir the batter until it is smooth.
Fill well-buttered (or paper-lined) muffin cups in the pan about two-thirds full, as shown in Figure 8, below.
- 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 the pan to get the muffins equalized. On the other hand, you do not want spend too much time on this, because the baking powder starts working as soon as it touches liquid.
Figure 8. Fill the muffin cups about two-thirds full with batter.
Bake at 425°F for 15-20 minutes, or until nicely browned and baked through.
- Remember to use oven mitts when putting the pans in the oven and when taking them out again.
- Place the muffin pan on a cooling rack, as shown in Figure 9, below, for a few minutes, and then tip the muffins out. Let them cool for a few more minutes before handling (or sampling!) them.
Figure 9. Place the muffin pan on a cooling rack for a few minutes before tipping the muffins out.
Repeat steps 4-9 but this time use no baking powder.
- Be sure to keep track of which batch is which as you make more muffins!
- Repeat steps 4-9 but this time use 1 tsp. baking powder.
- Repeat steps 4-9 but this time use 4 tsp. baking powder.
Compare the four different batches of muffins. In your lab notebook, make a data table similar to Table 1, below, and record your results and observations in your data table.
- Measure the height of each muffin in each batch (in centimeters [cm]) and record your results in your data table.
Calculate the average height for each batch and record this in your data table (in the bottom row).
- Note: If one muffin is much smaller than all the others, do not include it when calculating the average height.
- If you have a kitchen scale, you should also measure the weight of each muffin (in grams [g]). Record the weight of each muffin in a data table in your lab notebook similar to Table 1. Also calculate the average weight for each batch and record this in your data table as well.
- More advanced students can also calculate the density of each muffin (see the Make It Your Own section).
- Slice some representative muffins from each batch so that you can compare the texture. Record your observations in your lab notebook.
Although it is definitely not the case for most chemistry experiments, for this one it is OK to do a taste test! Remember to record your observations.
- Tip: For obvious reasons, it is important to do the size and weight measurements before the taste test!
|Muffin||No Baking Powder||1 tsp. Baking Powder||2 tsp. Baking Powder||4 tsp. Baking Powder|
Make bar graphs of your results.
- Make a graph showing the average height (in cm) of each batch of muffins on the y-axis (the vertical axis) and the amount of baking powder in the batch on the x-axis (the horizontal axis).
- If you measured the weight of the muffins, make a graph showing the average weight (in g) of each muffin batch on the y-axis and the amount of baking powder in the batch on the x-axis.
- If you calculated the density of each muffin, make a graph showing the average density (in g/cm3) of each muffin batch on the y-axis and the amount of baking powder in the batch on the x-axis.
Try to draw some conclusions based on your results.
- How did changing the amount of baking powder in the muffin recipe change the resultant muffins? How did it affect their height and weight (if you measured it)?
- Which muffin batch did you prefer and why?
- Can you explain your results in terms of what baking powder does? Tip: You may want to try re-reading the Introduction to explain this.
If you like this project, you might enjoy exploring these related careers:
- 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.
- You could try adding different amounts of baking powder than what you tested in this science project. Is there a point at which it looks like adding additional baking powder does not affect how the muffins turn out? What about adding less baking powder than what is used in the original recipe — how little baking powder can you add to still have muffins that are similar to the ones made using the original recipe?
- For a related experiment, see the Science Buddies project Chemistry of Baking Ingredients 2: Can Baking Soda Substitute for Baking Powder in a Recipe?
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