This article is one of a series of Experiments meant to teach students about how science is done, from generating a hypothesis to designing an experiment to analyzing the results with statistics. You can repeat the steps here and compare your results — or use this as inspiration to design your own experiment.
The best part of a kitchen-science experiment is baking it up. For Cookie Science, my goal is to bake up and test my first hypothesis. I want to share my delicious cookies with my friends. But one of them, Natalie, can’t eat gluten, a protein found in wheat (and therefore in cookies). Since Natalie can’t eat gluten, I need to design a cookie recipe without it. My goal is to have it taste as close to the regular cookie as possible. To achieve that, I’m beginning a series of experiments.
From reading about the role of gluten in baking, I came up with my first hypothesis: that replacing wheat flour with a gluten-free type is not enough to yield a comparable cookie. But to confirm that, I now need to bake up some samples.
When conducting an experiment, it’s important to make sure to control — keep unchanged — as many variables as you can. A variable is any part of your experiment that can be changed to influence the results. For my experiment, I will be changing one variable: the flour. Other variables such as time and temperature must remain the same.
I am basing my cookie on the Alton Brown “chewy” recipe. I like this recipe because instead of measuring flour by volume (teaspoons and cups, for instance), this one measures flour, butter, chocolate, milk and sugar by weight. Weighing these ingredient helps to ensure each batch will be consistent.
My control cookies will contain:
- 8 ounces unsalted butter (Land O’ Lakes brand)
- 12 ounces bread flour (King Arthur brand)
- 1 teaspoon kosher salt (Morton brand)
- 1 teaspoon baking soda (Arm and Hammer Brand)
- 2 ounces granulated sugar (Domino Brand)
- 8 ounces light brown sugar (Domino Brand)
- 1 large egg (organic store brand)
- 1 large egg yolk (organic store brand)
- 1 ounce whole milk (organic store brand)
- 1 1/2 teaspoons vanilla extract (McCormick brand)
- 12 ounces semisweet chocolate chips (Enjoy Life brand, dairy, nut and soy free)
As my control recipe, these cookies are the ones I will compare the new recipes against.
Notice, I not only listed all of the ingredients, but also the brands I used. Most scientific papers list the products they use and the company or brand of each. This is not because I, or any scientist, endorses certain brands over others. Instead, it is to help other scientists who might want to try and repeat the experiment in precisely the same way. Using the same products from the same places helps scientists reproduce an experiment as closely as possible.
For my two experimental cookies, I substituted the wheat flour with an equal quantity of gluten-free flour blend (made from a mix of tapioca starch, garbanzo beans, potatoes, sorghum and fava beans) or an equal amount of a gluten-free flour made from rice (both of these flours are from Bob’s Red Mill). I am testing more than one type of gluten-free flour because I want to make sure that any differences in how people rate my cookies are due to the flour being gluten-free, not due to one gluten-free flour tasting funny or having a strange texture.
I want to make sure that my cookies are baked at the same temperature. So I am baking them together. To do this, I carefully prepared all of the recipes in separate bowls at the same time. I weighed flour for each of the batches. I then weighed the other dry ingredients into each mixture. As I went, I carefully checked off each ingredient in my lab notebook to make sure I didn’t leave anything out.
Once I had added all dry ingredients together for each of batch, I began adding the wet ingredients. I added each new ingredient to each batch at the same time, so one batch would not sit out longer than another. Finally, I added food coloring to each batch. My control was red, the gluten-free flour blend was blue and the rice flour batch was green.
Then I put all three bowls of dough into the refrigerator for an hour (as the recipe called for). I cleared out my fridge to make sure I could put all three bowls on the same rack. This way one batch should not end up in a colder spot than another.
Rev up the oven!
After I finished preparing the dough, I preheated my over to 190° Celsius (375° Fahrenheit). When the dough had cooled, I scooped small balls of it onto the cookie sheet. I used a mini ice cream scoop to ensure that all cookies started out the same size. I washed out the ice cream scoop carefully between each batch, to make sure that one batch would not contaminate another.
I kept the cookies spaced evenly on the cookie sheet. And I alternated rows of control, the gluten-free flour blend and the gluten-free rice flour. This way, one batch would not end up in a warmer spot in the oven (because yes, the temperature can vary quite a bit depending on where in the over you make your measurements). I then gently pressed four chocolate chips into each cookie, trying to space them evenly. I wanted to make sure that no one cookie was more chocolately — and potentially more delicious — than another.
Then, I slid my first batch into the oven and set the timer for 12 minutes. The recipe says to bake for 15 minutes, but I know that my oven runs a little hot on the edges. So I altered my procedure to account for this.
Bake and learn
Science often involves changing things up as you go. I wanted to put all of the batches on the same cookie sheet at once so that I could ensure they baked equally long and hot. Unfortunately, my first batch of cookies showed that this wouldn’t work. The gluten-free blend and rice-flour cookies spread out much more during baking than the controls did. They also baked much faster. This meant a fully baked control would have led to burning the gluten-free alternatives.
To solve this problem, I ended up having to bake each batch separately. Both gluten-free batches went in for only eight minutes each. I also had to spread out the dough from these batches more so that the cookies did not merge into each other as they baked. To make sure the baking sheets had a constant temperature before they went into the oven, I soaked each in cold water for one minute and dried it between each use.
Finally, I increased my chocolate chips from four to five per cookie (as the four chips looked very lonely on the finished snack).
When you are running an experiment, you may come across something that you didn’t anticipate. If you do, measure it!
I noticed, for instance, that as I baked my cookies the gluten-free types spread out much more than the control did during baking. I recalled from readings that gluten free flours produce a wider, thinner cookie during baking. I decided to measure how much my cookies spread out, and picked 10 cookies of each type at random to measure before and after baking. I will also incorporate these data into my next experiment.
After several hours and many, many batches of cookies, I was ready to have people taste them. Stay tuned for part two of baking it up, when I put my cookies to the test!
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bias The tendency to hold a particular perspective. Scientists often blind subjects to the details of a test so that the participant’s biases will not affect the results.
blinding (in research) The deliberate hiding of some important test information from a participant. For instance, a researcher might put a blindfold on participants before they eat something. This prevents them from being influenced by a food’s appearance. For a test of how well a drug works, researchers may give each person a capsule or shot. But only one group gets the real drug. Others might get an inactive “sugar pill” or injection of salt water. By not knowing if they got the real deal or an imposter, participants’ responses should not be biased for or against a particular result.
celiac disease (or coeliac disease in the United Kingdom) A disorder in which the immune system attacks the small intestine after it encounters foods containing gluten, a wheat protein compound. People with this disease suffer from stomach pain, constipation, diarrhea and a constant feeling of fatigue. They must avoid gluten-containing products like bread, cake and cookies.
control A part of an experiment where nothing changes. The control is essential to scientific experiments. It shows that any new effect must be due to only the part of the test that a researcher has altered. For example, if scientists were testing different types of fertilizer in a garden, they would want one section of to remain unfertilized, as the control. Its area would show how plants in this garden grow under normal conditions. And that give scientists something against which they can compare their experimental data.
gluten A pair of proteins — gliadin and glutenin — joined together and found in wheat, rye, spelt and barley. The bound proteins give bread, cake and cookie doughs their elasticity and chewiness. Some people may not be able to comfortably tolerate gluten, however, because of a gluten allergy or celiac disease.
hypothesis A proposed explanation for a phenomenon. In science, a hypothesis is an idea that hasn’t yet been rigorously tested. Once a hypothesis has been extensively tested and is generally accepted to be the accurate explanation for an observation, it becomes a scientific theory.
protocol (in science) A written procedure to describe how an experiment will be conducted. Protocols are written before an experiment is performed and are used to make sure that the experiment meets standards for fairness and good practice. Protocols also allow other people to attempt the same experiment and see if they can replicate previous results.
variable (in mathematics) A letter used in a mathematical expression that may take on more than one different value. (in experiments) A factor that can be changed, especially one allowed to change in a scientific experiment. For instance, when researchers measure how much insecticide it might take to kill a fly, they might change the dose or the age at which the insect is exposed. Both the dose and age would be variables in this experiment.