Bread Making Lab

Background

Bread-making is a fascinating intersection of chemistry, biology, and food science. Two of the most common types of flour used in bread-making are white bread flour and whole wheat flour. Though they may have the same protein content per serving (4g), the quality and characteristics of the bread they produce can be quite different. Understanding the science behind these differences is essential to learning how ingredients affect the final product.

The Role of Gluten in Bread

Both white bread flour and whole wheat flour contain protein, primarily in the form of glutenin and gliadin. When mixed with water and kneaded, these proteins form gluten, a strong, elastic network that traps gas produced by yeast fermentation. This gives bread its structure and allows it to rise.

White bread flour is made from the endosperm of the wheat grain and has a higher concentration of gluten-forming proteins. This helps create bread with a soft, elastic crumb and a higher rise. Whole wheat flour, on the other hand, includes the bran and germ of the wheat grain. While it still contains gluten-forming proteins, the bran and germ interfere with gluten development by cutting through the gluten strands. This results in a denser loaf with a more coarse texture.

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Fiber Content and Water Absorption

Whole wheat flour contains more fiber due to the presence of bran, which absorbs more water than the starches in white flour. As a result, whole wheat dough tends to be stickier and more challenging to knead. This increased water absorption affects the texture and moisture of the final bread product, often leading to a denser loaf.

White bread flour contains less fiber, allowing for smoother gluten development. This produces a lighter, fluffier loaf with larger air pockets. The lack of fiber also means that white bread retains less moisture compared to whole wheat bread, which may result in faster staling.

Flavor and Nutritional Profile

The flavor difference between white bread and whole wheat bread can be attributed to the bran and germ in whole wheat flour, which contribute a nutty and earthy taste. Whole wheat bread also has a higher nutritional profile due to the fiber, vitamins, and minerals present in the bran and germ. White bread, while softer and more refined in flavor, lacks these additional nutrients, as they are removed during the refining process.

Yeast and Fermentation

Yeast plays a crucial role in bread-making by fermenting the sugars present in the dough and producing carbon dioxide, which helps the bread rise. The bran and germ in whole wheat flour slow down gluten development and can inhibit yeast activity to some degree, leading to a denser loaf with a lower rise.

In contrast, white bread flour provides an ideal environment for yeast fermentation, allowing the dough to rise more effectively, resulting in a lighter and taller loaf.

Lab Purpose

In this lab, you will compare the qualities of bread made from white bread flour and whole wheat flour, using identical ingredient weights. By observing differences in texture, rise, moisture content, and flavor, you will gain a deeper understanding of how the type of flour influences the final product.

This lab will introduce you to key concepts in food science, including gluten development, water absorption, fiber content, and yeast fermentation, all of which contribute to the texture, flavor, and nutritional value of bread.

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Materials

• 3 cups white bread flour
• 3 cups whole wheat flour
• ¼ teaspoon salt
• 3 tablespoons vegetable oil
• 2 tablespoons sugar
• 1 tablespoon yeast
• 1 ½ cups warm water (for each bread type)
• Bread machine
• Spatula
• Ruler
• Cooling rack
• Scale (optional)

Procedure

Preparation of White Bread

1. Add ¼ teaspoon salt, 2 tablespoons sugar, 3 tablespoons vegetable oil, and 1 ½ cups warm water to the bread maker pan.
2. Add 3 cups of white bread flour on top.
3. Sprinkle 1 tablespoon of yeast over the flour.
4. Set the bread machine on a 58-minute menu and press start. Use a spatula to scrape the sides if flour sticks to the pan.
5. Once baked, remove the pan from the machine and let it cool for 5 minutes. Transfer the bread to a cooling rack.

Preparation of Whole Wheat Bread

1. Repeat the same steps as above, but substitute white bread flour with 3 cups of whole wheat flour.
2. Use the same machine settings and process.

Evaluation Activities

Students will evaluate the loaves the following day of the lab.

Visual Appearance & Texture

1. Shape: Measure the height of both loaves using a ruler. Record the results.
2. Crust Color: Observe and note the differences in the crust’s color between the white bread and whole wheat bread.
3. Surface Texture: Feel the texture of the crust—smooth, rough, etc.—and record the differences between the two loaves.

Internal Texture (Crumb Structure)

1. Cut slices from both types of bread and observe the crumb (the internal part of the bread).
2. Pore Size: Compare the size of the air pockets (pores) in each slice.
3. Softness: Press down lightly on the slices with your fingers to compare the softness and elasticity of the white and whole wheat bread.

Flavor and Aroma

1. Taste both types of bread and describe the flavor. Is one sweeter, nuttier, or more earthy? Record your observations.
2. Compare the aroma. Which bread has a stronger or more distinct smell?

4. Moisture Content

Optional: Weigh both loaves before and after baking. Calculate moisture loss based on the weight difference, noting any major disparities.

Data Recording

Students will complete the table below as they evaluate both breads.

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Lab Questions

1. Which loaf rose higher? Why do you think that is?
2. How did the crust color and texture differ between the white bread and whole wheat bread?
3. How would you describe the internal texture of the two breads? Which had larger air pockets?
4. What differences did you notice in flavor between the white bread and whole wheat bread? Which one did you prefer and why?
5. Based on the bread’s structure and texture, how do you think the fiber content of whole wheat affected the dough’s performance?
6. How might the difference in gluten development have affected the texture and height of the bread?