Introduction: How to Experiment With Bread Making, Yeast, and Gluten

By Magical Microbes
About: We make fun and educational STEM kits that let you play with microbes. Create electricity from the bacteria living in mud, or make bread while racing yeast!

With DoughLab (or the equivalent components from the store), you can design your own delicious bread experiments and learn about yeast! Before you start, here's the skinny on saccharomyces:

Yeast,a single-celled fungus that belongs to the same kingdom as mushrooms,is one of the most common microbes in the world. In the presence of oxygen, this fungus munches up sugars and produces carbon dioxide, or CO2, making bubbles in liquid or dough. (No wonder yeast means "bubbles" in old English and was dubbed saccharomyces, or “sugar fungus” in Latin!) This process of eating food and releasing waste is called “respiration.” Interestingly, even without oxygen, yeast continue to respire. However, instead of producing CO2, yeast will produce alcohols through a process called fermentation, making yeast a key player in beer and wine production.

Step 1: The Art of Experimentation

To design your own bread experiments, use the “Scientific Method":

The Scientific Method

  1. Purpose: What do you want to learn about?
  2. Testable Question: Turn your idea into a question that can be answered through experimentation.
  3. Independent Variables: Decide on your independent variables, the things you'll modify in your experiment (e.g., flour type, temperature).
  4. Dependent Variables (Measurables): Determine your dependent variables, the things you'll measure in your experiment (e.g., loaf rise time, bread taste, texture).
  5. Hypothesis: What do you expect the results of your experiment to be?
  6. Materials: List all the materials and supplies you'll need.
  7. Procedure: Write out each step so that someone else could repeat your experiment using your directions.

Analyzing Data

Once you’ve started your experiment, collect and analyze your data:

  1. Data Collection: Record what happens, especially to your dependent variables. Remember to include units, times of measurements, sketches, and any other observations.
  2. Data Display: Display your data so that others can easily understand it. Make graphs (line, bar, circle, or scatter) or a time series of sketches.
  3. Analysis: Examine your data, and describe any patterns, trends, and changes you see.
  4. Conclusion: Were you able to answer your testable question from your results? What did you find out? Were the results what you expected? Why or why not? Did anything go wrong along the way? Identify anything you'd do differently if you were to do the experiment again. Identify any new ideas or new questions that arise as a result of running this experiment.

Step 2: Prepare Your Experiment

Before you begin, plan your experiment! Determine which “independent” variables you’d like to change and which “dependent” variables you’d like to measure. How do your independent variables impact your dependent variables?

Independent Variables:

  • Sugar level
  • Yeast vs. no yeast
  • Rise time
  • Temperature
  • Water content
  • Water type (distilled vs. tap)
  • Other ingredients (yogurt, baking soda, salt, honey, etc.)
  • Can you think of more...?

Dependent Variables:

  • Yeast respiration rate (see below)
  • Dough expansion, AKA rising
  • Dough or bread texture
  • Dough pore size, AKA bubble size
  • Taste
  • Color, before and after baking
  • Can you think of more...?

Measuring Respiration Rate

“Respiration” describes the process of munching up food and releasing waste. Watching yeast respire involves putting gloves on top of your dough containers to capture your yeast's waste CO2 and seeing how fast this CO2 inflates the gloves.

Step 3: Sample Experiments

  1. How does yeast impact dough and bread?
  2. How does gluten impact dough and bread?
  3. How does temperature impact yeast’s “respiration” rate?
  4. What ingredients impact yeast’s respiration rate?

Bonus Experiment: Sourdough (Quick version)

Ever wondered what makes sourdough bread sour? Many types of bacteria, such as lactobacillus, produce lactic acid as a waste product when they eat, which makes bread and yogurt sour. In sourdough, these bacteria typically outnumber yeast 100-to-1! Try adding a bit of yogurt with active cultures to your dough to see if you can grow lactobacillus and make tasty sourdough bread! For the traditional method of making sourdough, skip to Step 10.

Step 4: Assemble Materials

You'll need the following materials, included in Magical Microbes's DoughLab, or available at your local grocery (or pantry!):

  • High-gluten flour
  • 3 large packets of cane sugar, or a bag of sugar
  • 6 small packets of salt, or a box of salt
  • Yeast packet
  • Measuring spoon (1/4 teaspoon)
  • 3 Graduated plastic containers
  • 3 Mixing sticks, or spoons
  • 3 Latex gloves
  • 3 Foil baking pans

Note: You'll also need a pen and scissors.

Step 5: Prepare Dry Ingredients

  1. Wash your hands. (Save the gloves for your yeast!)
  2. Optional: Put down newspaper on your workspace.
  3. Label your three clear containers. In these instructions, container #1 is the “Control,” container #2 has “Added Sugar,” and container #3 has “No Yeast.”
  4. For all three containers, add flour up to the 200ml mark (7/8 cup for each container).
  5. Add 3 large packets of sugar (1/4 tablespoons total) to container #2, the “Added Sugar” container.
  6. Add 2 small packets of salt (3/4 teaspoons total) to each container.
  7. Open the yeast packet using a pair of scissors. Add 3 small spoonfuls of yeast (3/4 teaspoon total) to container #1 (the “Control”) and Container #2 (the one with “Added Sugar”). Level off each spoonful (1/4 teaspoon) of yeast before adding it to your container. No yeast goes into container #3.
  8. Mix the dry ingredients together with a mixing stick (or clean spoon). Be sure to use a new stick (or spoon) for each container so that you don’t cross-contaminate the mixtures. Keep your mixing sticks in their corresponding containers. You’ll need them again later.
  9. Gently knock the jars down on the table a few times to level the mix.

Step 6: Activate the Yeast

  1. Get a big glass of luke-warm water from the sink. All containers should get the same temperature water.
  2. Pour the water over the dry ingredients up to the 350ml mark for each container (2/3 cup of water). Pour quickly so you've finished pouring before the water starts to seep into the flour. This ensures the same amount of water is poured into each container.
  3. Mix until the consistency is smooth. Use the same mixing sticks (or clean spoons) from Step 8 to avoid cross-contamination.
  4. Work out any flour clumps. If your dough is dry and difficult to mix, add water until all your doughs are the same gooey consistency.

Observation Time: Try pulling up the sticks to test the dough consistency. Why might it be stretchy?


What's Happening?

With the addition of warm water, yeast “activate,” meaning they begin to swim, eat, and multiply. This process starts immediately. Yeast prefer warm conditions which is why warm water is recommended.

The addition of water also allows the straggly glutenin and gliadin proteins to bond together to form gluten. Gluten proteins expand and become tangled up with other straggly gluten proteins nearby. This causes dough to become stretchy and gooey.

Step 7: Knead

  1. Optional messy-but-fun step: With washed hands, scoop up the dough and knead it (fold it in on itself repeatedly). Wash your hands between each container to prevent contamination.
  2. After kneading for a few minutes, squish the dough back into the container, and flatten the top.

What's Happening?

One of the reasons bakers knead dough is to uncoil gluten compounds and encourage more linkages between them. This strengthens the gluten network and gives bread a more uniform, chewy texture.

Once you let the dough rest, the yeast go to work! They start munching up sugars in a process called “respiration.” When yeast have lots of oxygen around, they perform “aerobic respiration,” releasing carbon dioxide (CO2) as a waste product. In this experiment, the gas fills up the gloves. The happier the yeast, the faster their respiration rate, and the faster the gloves will inflate!

Step 8: Rise

  1. Stretch the opening of the gloves tight over the tops of the jars so that they just cover the top rim.
  2. Let the containers rest at room temperature (out of direct sunlight) for 30-45 minutes, or until the dough has reached the top of the container.

Observation Time: Which glove inflated the fastest? Why? Is there is a difference in bubble size or consistency in the different doughs?

Step 9: Bake and Eat!

  1. Now, get ready to bake by turning the oven to 350 F (adult supervision required). Mark the side and bottom of the foil pans with “1”, “2,” and “3”, by indenting them with your finger or by using a pen.
  2. Remove the gloves and place each ball of dough into the corresponding tin. Alternatively, shape your own foil packets (caution: your dough might ooze at the seams if you try this, so pinch the corners tight)! For a crispier crust, rub the top of your dough with oil or water.
  3. Bake the tins together for 20-30 minutes until the top of each loaf is golden-brown (adult supervision required). Let the loaves cool for a few minutes, then enjoy the results of your experiment!

Observations Time: What differences do you observe in your breads? Think about taste, texture, density, color, etc. Can you explain what caused these differences?

Step 10: Bonus: Catch Your Own Yeast! (and Make Sourdough)

For this experiment, you'll want a supply of whole wheat flour.

1. Prepare your Microbe Bait...

  1. In a clean jar, add flour up to the 200ml mark (3/4 cup + 1 tablespoon).
  2. Add room temperature water up to the 350ml mark (1/2 cup + 2 tablespoons). If you've got non-chlorinated water, bottled or filtered, use it!
  3. Mix well with a spoon or mixing stick.
  4. Place a clean glove over the top of the jar such that it covers the top rim.
  5. Store your fledgling starter (dough) in a warm place.

...and Wait

Now that you’ve set up your microbe bait, it’s time to wait. Naturally occurring yeast are probably starting to eat and replicate, though it may take time to see any activity.

2. Let your Starter Culture

  1. After 24 hours, remove half of your dough, and mix in 7 scant tablespoons of flour and 4 tablespoons of water. Put your glove back on the container. If your dough looks good, you can save the dough you removed in an air-tight container in the fridge and bake it later! Note: Do not eat your mixture raw. Although this is a time-tested method, there's no way to guarantee that good microbes are present and bad ones aren't. Use your eyes, nose, and the help of a microbially responsible adult to decide whether or not to use your mixture for bread.
  2. Repeat Step 1 daily until your starter is bubbling and yeasty or fruity smelling.

Once you see bubbling in the mixture and the glove inflating, your yeast are replicating! You’ve probably also got some acid-producing bacteria in there that will give you sourdough. If you see weird colors, fuzzy patches, or anything else that looks like mold, you’ve caught some other moldy microbes, and you’ll need to start your sourdough starter over.

3. Maintain your Starter

  1. Now that your culture is alive and well, continue to remove half and mix 7 scant tablespoons of flour and 4 tablespoons of water into your container every 12 hours. Put your glove back on your container after each addition. Repeat this step until your mixture looks slightly foamy, which can take up to 2 weeks.
  2. Once your mixture looks foamy, repeat step 1, and if your mixture doubles in volume in about 6 hours, it's time to use. Otherwise, continue repeating step 1 until your mixture doubles in 6 hours.
  3. Now, repeat step 1 one last time, and once your mixture is doubled in size and actively bubbling (a few hours), take what you need to use in your sourdough recipe of choice, and place the remainder in the fridge.

4. You're ready to bake! Use your starter from step 3.3 with any recipe you please!

Long-term care: Store your starter in the fridge, and feed by mixing in 7 scant tablespoons of flour and 4 tablespoons of water once a week. When you're ready to use your starter, take it out of the fridge, and return to Step 2, "Activate your Starter."

Step 11: Bonus: the Great Mold Race!

For microbes, some foods are easier to digest than others. Nutrients that are easily digested are called “bioavailable.” Foods that have a lot of “bioavailable” nutrients, like bread and milk, often mold or sour quickly, which is why many store-bought breads contain preservatives and other chemicals to prevent microbes from growing on them.

The following is a simple experiment that will show you which breads have the most “bioavailable” nutrients and the impacts of preservatives:

  1. In a clean plastic sandwich bag, place one small (2” x 2”) piece of damp paper towel.
  2. Place a slice of bread in the bag.
  3. Seal up the bag and let it sit at room temperature out of direct sunlight.
  4. Repeat steps 1-3 for the different breads you’ve made and/or breads from the store.
  5. Now, wait...

Check the bags daily to see which pieces of bread are molding. Record what percentage of the bread is covered by mold, and see if the mold coverage follows an exponential growth curve. What differences do you see between the breads? Can you explain the results you find?

Step 12: Bonus: Gluten Isolation (Make Your Own Seitan!)

Wheat flour contains a protein, called gluten, which adds to the stretchiness of dough and the chewiness of bread. The following activity demonstrates how you can isolate gluten from flour to make seitan:

  1. In a container, mix 250 ml (1 cup + 1 tablespoon) of high-gluten flour with 150ml (1/2 cup + 2 tablespoons) of tap water.
  2. Knead the dough in your hands until it's a compact ball.
  3. Cup the dough in your hands, and run cold water over it continuously. The cold water will dissolve the starch in the dough, but it won’t dissolve the gluten.
  4. Continue rinsing and gently massaging the dough until the water is no longer milky-looking.

You now have a ball of gluten protein! Play with it, and notice that the ball is comprised of tightly-woven clumps of gluten. Try tearing those clumps apart to see how strong gluten strands can be.

After playing with your ball, knead it back together, and pop it in the oven at 450 degrees F for 15-20 minutes (with adult supervision). You’ve created seitan, a food enjoyed all around the world, commonly with soy sauce, ginger, and garlic. Yummm!

Step 13: Taste Tips

Trust the Crust

For serious bakers, crust is often the most important part of bread. If you’re a fan of tough, crunchy crusts, here are some tips:

A) Cut 1/2-inch deep slits into the top of your dough before baking.

B) Rub water or oil over the top of your dough before baking.

C) Use a higher oven temperature (and shorter bake time).

Perfect Pizza Dough

Through your experiments, you’ve learned different ways to make your bread denser or fluffier. Use that knowledge to create your own perfect pizza crust. Or, try:

A) Olive Oil: Smear olive oil onto your baking sheet and over your flattened dough before baking.

B) Salt: Add a couple more pinches of salt to the top of your flattened dough before baking.

When in Doubt, Add Chocolate

There are hundreds of ways to make dessert breads and cakes. We encourage you to experiment with the common additives below to find your own perfect recipe:

A) Vegetable Oil, to make the bread/cake moister

B) Eggs, to add to “fluffiness” and moisture and to help bind ingredients

C) Sweeteners: Sugar, bananas, apple sauce, sweetened chocolate, and even carrots are common ingredients that add sweetness!

Step 14: A Brief History of Bread

About 30,000 years ago, humans began making bread. Early bread was made of a grainy paste and was dense and flat, making it a perfect high-energy food that could be carried and stored. Today, we call these "flat breads," and they include breads from all over the world, like pita, tortillas, and naan.

Roughly 12,000 years ago, people living in modern-day Iraq first domesticated wheat and barley, leading to a massive rise in bread consumption during a period called the "Agricultural Revolution." All over the world, grains, like wheat, barley, rice, and maize started cropping up, due to humans’ careful selection of nature’s biggest and best grains. To grow these grains, people settled down and began to farm and build thriving communities. Populations boomed with these energy-rich, storable foods.

It was only a few thousand years ago that people started using yeast to make bread fluffier and more delicious. Dough was left out in the open to "rise," as yeast (which naturally live on grains and other foods) would munch up sugars and release gas bubbles into the dough. To make this process faster, people would add pieces of old dough, mashed grapes, or beer foam, which are all full of yeast.

Bread has changed quite a bit over the years. Many new ingredients, like vitamin C and anti-microbial preservatives, are now often added to bread to allow bakers to use less-expensive grains and to lengthen shelf-life. Bread started out consisting of only 3 ingredients, grain, salt, and water, but today, bread often contains over 30 ingredients in just one loaf! Bread-making all over the world continues its various traditions, in addition to enjoying new flavors, ingredients, and techniques.