The Science Behind Bread (Experiment)

Piper, Kira and Emily

White Bread

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Intro- In our Biology class, we made bread in order to better understand photosynthesis and cellular respiration. We are novices in the bread making business and we were tasked with figuring out the necessary ingredients and the amount of each ingredient as well as the science behind bread making.

Yeast

Yeast are actually living organisms! They are eukaryotic, single-celled organisms. Yeast plays a very important role in bread making. Yeast is capable of converting sugar into carbon dioxide and alcohol. In doing this, it causes the bread to rise. The warm water added to the dough “activates” the yeast. If the water is too hot, it will kill the yeast. If the water is not hot enough, the yeast will not wake up.

Cellular Respiration

The process yeast uses to make carbon dioxide and alcohol is called alcoholic fermentation. This process is a variation of cellular respiration, or the process of turning oxygen and sugar into energy, carbon dioxide, and water. Cellular respiration takes place in the mitochondria and it is used by humans and all other organisms to make energy.  The chemical equation for cellular respiration is 6O2+ C6H12O6 → 6H2O+ ATP+ 6O2. There are two types of  respiration: aerobic, which requires oxygen, and anaerobic, which does not. Within anaerobic respiration there is alcoholic fermentation for plants and lactic acid fermentation for animals.

Flour

Flour was wheat before it became flour. Wheat is a plant, and like all other plants it goes through photosynthesis. In the process of photosynthesis, glucose and oxygen is made from carbon dioxide and water. Although the flour no longer performs photosynthesis, when it was turned into flour some glucose that was produced was most likely left behind. Since yeast uses glucose to perform alcoholic fermentation and make the bread rise, the flour can be used as its “food” along with sugar. Flour is made up of glutenin and gliadin. When combined with warm water, the glutenin and gliadin turn into gluten. This is important in bread making because it strengthens the bread and provides structure.

Carbon Cycle

Making bread also plays a role in the carbon cycle. Because anaerobic respiration is being performed, carbon dioxide is being produced. Therefore, when bread is made, carbon dioxide is released into the air.

The Science Behind the Ingredients

Originally, our team was given a simplistic recipe for plain, white bread. This recipe involved flour,  120 degree water and yeast. Our job was to add ingredients that would produce better bread and understand the science behind what made those ingredients work well.

Butter- Based off of research, butter makes bread more tender and increases elasticity. It also adds a lot of flavor. However, it can cause the bread to rise slightly slower so we decided to only put ½ Tbsp of butter in our recipe. We figured this way we could still get the flavor without the negative effects on the rising speed.

Salt- Salt is another preference ingredient we chose to add. Like butter, it adds flavor but it also decreases rising time. We added only a pinch of salt to our recipe because we know that a little bit of salt goes a long way in terms of flavor. Also, we didn’t want the decrease the rising speed.

Sugar- Sugar, or glucose, is food for the yeast. Therefore, adding sugar will increase rising time. In our research we found that you should not add more that 2 teaspoons per cup of flour. Based off of that proportion, we could add up to 1 teaspoon of sugar. We chose to add ¼ teaspoon because we wanted to play it safe, and we didn’t want really sweet bread.

Before we made our final product, we had a day to experiment with and tweak our created recipe. We did not bake our experimental bread, but we monitored its rising time for 30 minutes. There was a control bread that we compared our bread to. The control bread was made with only flour, yeast, and water. We were very happy with the results of the our bread. It rose slightly more than the control bread and when we broke it apart after 30 minutes of rising, it had lots of holes which meant that alcoholic fermentation occurred. We decided not to change our recipe at all because we had good results.

Now that you understand the science behind bread making, here is the procedure we followed:

In a ziploc baggie, mix together ¼ teaspoon yeast and ¼ cup of flour

Heat 4 tablespoons of water to 120 °F - 130 °F (1 minute in the microwave). Then slowly add the 4 tablespoons of heated water to the baggie and stir to combine.

                        Add ¼ teaspoon of sugar

Let mixture sit for 10 minutes in order for the yeast to activate.

Mix another ¼ cup of flour into the baggie

Add ½ Tbsp of butter and a pinch of salt to the baggie

Take the dough out of the baggie and knead it for one minute.

Roll the dough into a ball

Place the dough ball under a heat lamp for 30 minutes.

Place the dough ball in a cupcake pan and bake for 15 minutes in 375 degrees.

Here is our final product!

Reflection

We were successful in making bread, however it did not turn out how we thought it would. It was very hard, dry and bland. We had the right ingredients but not the right amount. If we were to do this again we would use more butter for flavor, and a little bit more sugar to make the bread rise more. Overall, we consider this bread to be a failure. Although it looked delicious and smelled delicious, it tasted like cardboard. However, we learned a lot in the process. If we were to make bread again, it would turn out a lot better.