Science Writing ARCHIVED Pandemic Version

YeastPilot Experiment

Directions

For your pilot experiment, your goal is to quantify how two things, temperature and pH, affect one specific growth outcome: the length of time it takes for a quantity of bread dough to double in volume.

The steps below describe how to set up a single replicate for each of 4 experimental conditions. Each student should complete at least three replicates in total. You will not have enough jars to do all three at the same time -- it's up to you how you divide things up. In other words, you could do the entire procedure once, then again, and again after that - OR you could follow the instructions in triplicate. Either is fine.

Step 1

Create a set of 4 “graduated cylinders”.

To quantify dough volume, you will be placing the dough into cylinder-shaped Mason jars. So before you begin, you will need to add volume markings to a set of 4 jars to turn them into “graduated cylinders.” Fifty-mL increments should work well. To create your volume markings, start by filling a 50-mL plastic centrifuge tube with water up to the 50 mL mark. Pour the water into one of your jars and mark and label the line with a Sharpie. Then pour this water into your next jar and repeat the same process for all your jars. Once this is complete, add another 50 mL to label the 100-mL volume. Repeat this whole process until all of your jars have markings in 50-mL increments up to a total of 300 mL.

Also label each jar with a unique number or letter to help keep track of which jar is which.

Step 2

Prepare your dough.

A standard ratio of ingredients for bread baking is to use what’s called the “baker’s percentage” (by weight): 100% flour, 60% water, 3% fresh yeast, and 2% salt (Ruhlman 2009). In other words, if you were to prepare a small loaf, you could do so by using 100 g of flour, 60 g of water, 3 g of yeast, and 2 g of salt – just around the right amount to make enough dough for a personal pizza, or two dough balls for this experiment.

Although it is most accurate to measure out these ingredients based on their mass, this requires access to a scale. Since we may not have access to a scale with an appropriate degree of precision, it may be simpler to work with volume-based measurements instead. The amounts in the table below will yield enough dough for 2 jars. (If you add the optional ingredients, this recipe makes dough that should taste pretty good. Make sure you and your teammates reach an agreement about whether to add or omit the optional ingredients!)

Dough Mixtures

Step 3

Create the pH x temperature treatments

Neutral pH: Prepare a single ball of dough by adding the flour, yeast, salt, and optional ingredients to the water, and then mixing until the dough starts to hold together. You should also make a decision about the total length of time for mixing the dough and keep it standard. I would recommend somewhere between 1-3 minutes. Divide this ball of dough in half.

Temperature:
- Put one dough ball into one of your prepared mason jars. Measure and record its starting volume. Then place in the refrigerator.
- Repeat with the other dough ball, placing the jar in a room temperature location.
- Put a thermometer next to each cylinder, give the thermometer at least 180 seconds to adjust, and record the starting temperature.

Acidic dough (pH = 4): Start by measuring the pH of the water you are working with, using a small piece of pH paper. For your acidic dough, add some vinegar to the water, a few drops at a time, and then retest with the pH paper to get a feel for how much vinegar you will need to add in total.

Temperature: Once you have reached a pH of 4, proceed with the same temperature steps described above.

Tip #1: your data collection will be easier if you place the neutral and acidic doughs in the refrigerator at the same time!

Tip #2: Your jars should not be sealed! They can be uncovered, or just loosely covered with a paper towel or tissue.

Step 4

Collect Data

Tracking changes in dough volume. One of your goals for this pilot experiment is to determine how long it takes for your dough to grow, but the timescale may vary dramatically, from a range between minutes to days. Therefore, I recommend checking your dough volumes according to the following schedule: 15 minutes, 30 minutes, 45 minutes, 1 hour, 1.5 hours, 2 hours, 3 hours, 6 hours, 12 hours, 24 hours, and beyond 24 hours, in 24-hour increments as appropriate. End your measurements after you collect at least 3 measurements in a row that are similar to each other (this does not include any measurements where the dough volume has not changed at all yet from the starting volume).

Tip: Make yourself a table and checklist to keep your data organized, and set a timer to remind yourself to check your experiment!

What to do with the dough at the end?

If you have access to a kitchen, there are a number of different tasty things you can do with the dough after your experiment is over. If you roll it thin, you can cook it in a frying pan over medium heat for a tortilla-like experience. Or, as suggested above, top it with your favorite pizza toppings and bake it in the oven at 350 degrees F for 15-20 minutes until the cheese is melted and starting to brown. You can also shape it into a roll and either bake it right away (also 15-20 minutes at 350 degrees F) or put it into the freezer to bake it later.

Team Check-In Meeting Midway Through the Pilot Experiment

At the end of the first week, arrange a time to meet face-to-face as team. Your choice whether that’s in person, Zoom, Google Meet, conference call, or something else -- but IT CANNOT BE A TEXT CHAIN OR GROUP CHAT! You must actually be able to speak to each other!

At your check-in meeting, you should accomplish the following things. You'll be uploading your notes and answering a few questions in the Pilot Check-in: Team Assignment in Canvas

Sharing Observations

Choose one person to take notes in their lab notebook.
Each team member should describe what they have observed from their experiments so far.
- Did anything surprising happen?
- Were there any challenges that came up? If so, were they able to resolve the problems? If not, what steps need to be taken next? Should this be brought up in your meeting with me?
- Would it be useful to repeat or redo any aspects of the experiment? If any aspects are redone, what changes will be made?

Team Sharing & Assignment

Upload your discussion notes to Canvas (if notes were handwritten, upload a photo)
Answer the Team Assignment questions in Canvas
Schedule your team meeting with me
Every student should write any decisions made at the meeting down in their own lab book. Take a photo of your personal notes and upload it to Canvas.

Individual Data Sharing & Assignment

use your phone to scan your notes, and upload the resulting pdf to your team's shared drive
enter your data into your team’s shared Google Sheet
answer questions on Canvas (Pilot Wrap-up: Individual Assignment)

Team Meeting at the End of the Pilot Experiment

Arrange a time to meet face-to-face as team (your choice whether that’s in person, Zoom, Google Meet, conference call, or something else -- but IT CANNOT BE A TEXT CHAIN OR GROUP CHAT! You must actually be able to speak to each other!)

At your meeting, you should accomplish the following things. You'll be uploading your notes and answering a few questions in the Pilot Wrap-up: Team Assignment in Canvas

Choose one person to take notes.
Verify that all students have added their data to the shared data sheet
Does anyone have questions about the data?
Did anyone encounter unexpected problems or challenges while collecting data?
Is there anything from this experience that will be especially valuable in planning your main experiments?

Team Sharing & Assignment

Upload your discussion notes to Canvas (if notes were handwritten, upload a photo)
Answer the Team Assignment questions in Canvas

References

Ruhlman M (2009) Ratio: The Simple Codes Behind the Craft of Everyday Cooking. Scribner, New York, NY

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