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Investigating Alcoholic Fermentation And The Affects Of Yeast On Dough

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Biology Lab Report

Investigating Alcoholic Fermentation and the Affects of Yeast on Dough

Aim: The aim was simply to investigate whether or not yeast had any affect on causing dough to rise when baked and to experiment with alcoholic fermentation eg. to see if it gave off carbon dioxide.

Introduction: Following a few weeks of fermentation theory, groups of three to four were assigned and told to conduct a series of experiments involving the affects of fermentation. My group consisted of myself, Won Jin, Brendan and Sun-Ho and we chose to investigate alcoholic fermentation and the affects of yeast on dough, more specifically to see if yeast caused the dough to rise in anyway. We followed the instructions in our biology textbook on page 129.

Hypothesis: According to what I've learned, I would expect that the yeast does indeed cause the dough to rise due to the carbon dioxide gas given off by the yeast. For our alcoholic investigation, I can safely assume that carbon dioxide will be given off as the formula for anaerobically respiration in alcoholic fermentation for turning glucose into alcohol is [ Glucose -> Alcohol + Carbon Dioxide + Energy ] so obviously Carbon Dioxide is a part of this. Also I assume that the fermentation will give off heat and the sugar will probably be turned into alcohol.

Materials: ca. 100 g flour



10 per cent solution Glucose

Liquid Paraffin

Four Test Tubes

Lime Water (Used as an indicator)

Practical: Our first experiment was to see if yeast impacted dough in anyway and to do this we brought in supplies such as flour and yeast. We followed the instructions and made three groups of dough. For each group we added 50 g of flour and added a little bit of water while mixing it. Due to my lack of "kitchen skills" I had to throw away my first two attempts, as they had gotten too sticky. But like they say, third time's the charm and we finally made suitable dough.

We mixed warm water and yeast together in a bowl and added about 10 g of sugar, which is necessary for the dough to expand. We split the dough into two smaller mounds and added the yeast solution with only one of them to see the difference of dough with yeast and dough without yeast subjected to the same conditions to analyse the difference.

We placed both mounds of dough on top of a windowsill where we would leave it for an hour. We though this was a suitable place as the sun had already caused the surface to warm up. After an hour, the Dough mound with yeast did rise while the Dough mound without, didn't. Not much of a surprise. I'll return to the rest of our results in my conclusion.

For our second experiment (Alcoholic Fermentation) we moved to the Chemistry lab, from the kitchen, in order to better our chances of conducting a good experiment in a suitable environment. Our teacher, Mr. Barling, provided the Liquid Paraffin used in this experiment.

We poured the 10 per cent Glucose solution into a test tube and boiled it to be rid of any excess oxygen that could contaminate the experiment by affecting the yeast. After cooling the test tube, we added a little Yeast and poured



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