The Effects of Alcohol Concentration on the Fermentation ...

1 Fermentation lab report 1 The Effects of Alcohol Concentration on the Fermentation Ability of Yeast By: Drew Bowles Biology 1015 November 14, 2012 Lab Partners: Jared, Sam, Caroline Fermentation lab report 2 introduction Fermentation is an anaerobic process that takes place when oxygen is not present to convert glucose to carbon dioxide and water. If yeast is in a condition where no oxygen is present, alcoholic Fermentation will maintain glycolysis (Audesirk, Audesirk & Beyers, 2005). Yeasts are unicellular eukaryotes that are able to live with or without oxygen. In aerobic conditions, yeasts metabolize sugar to carbon dioxide and water. However when yeasts are in anaerobic conditions they produce ethyl Alcohol and carbon dioxide through Fermentation (Kulp & Lorenz, 2003).

2 The purpose of this experiment was to determine the Effects of Alcohol Concentration on the Fermentation ability of yeast. The optimal Alcohol Concentration for the Fermentation of yeast is 12-14% (Buikema & Sarmadi, 2012). A Concentration above 14% would likely result in the Alcohol killing the yeast so it is unable to complete the process of Fermentation . The highest optimal Alcohol Concentration for yeast Fermentation is 14%, so I expected any concentrations higher than 14% would cause Fermentation to stop and cease the production of CO2. At the Alcohol Concentration of 12-14%, I expected the yeast Fermentation to produce the greatest amount of CO2 because it is the optimum Concentration . METHODS First, we mixed a yeast recipe that would be inserted into the different concentrations of Alcohol .

3 We then measured the Alcohol concentrations of 8%, 12%, 14% and 16% into separate tubes. Each Concentration was repeated in two tubes so that we ended up with 8 tubes of Alcohol concentrations. Then we added as much water as Fermentation lab report 3 was needed to each test tube in order to equal the volumes of all the tubes, no matter the Concentration of Alcohol . Next, we marked the level of volume in each test tube so we could later determine the amount of CO2 that was produced by measuring the difference in volume. We inserted the same amount of yeast into all 8 test tubes and allowed them to sit and complete the Fermentation process for 20 minutes before we checked their progress. After 20 minutes, we marked the new volume level of each test tube.

4 Lastly, we measured the change in volume that occurred in each test tube in order to determine the amount of CO2 that was produced. RESULTS The average change in volume in the two test tubes that contained only 8% Concentration of Alcohol was .6cm. In the test tubes that contained 12% Alcohol , the average change in volume measurements was .45 cm. Increasing the Alcohol Concentration to 14% gave us a volume change of .25cm in both test tubes. Finally, the 16% Concentration test tubes only changed volume by .1 cm in both tubes. When all of the volume changes are compared to each other, the 16% Alcohol Concentration obviously produced the least amount of CO2 whereas the 8% and 12% concentrations produced the most (Figure 1).

5 When I conducted a one-tailed T-test to compare the volume changes, I got a p-value of Since this number is greater than , there is no statistically significant difference between the groups. Fermentation lab report 4 DISCUSSION The results supported my hypothesis in that once the Alcohol Concentration passed 14%, the production of CO2 would significantly decrease. However, I did not expect more CO2 to be produced at the 8% Concentration than the 14% Concentration , considering the optimum Alcohol Concentration for Fermentation is 12-14%. By conducting this experiment, we have achieved the results that prove Alcohol decreases Fermentation in yeast at concentrations higher than 14%.

6 We have also reached the conclusion that lower concentrations of Alcohol (between 8% and 12%) were actually more ideal for Fermentation than the higher optimum Concentration of 14%. A design that may have given us more accurate results for this experiment would have been to increase the Alcohol Concentration by 1% for each test tube. For example, we could have started at 8% and continued on to 9% then 10% until we eventually reached 16%. This way, we would have obtained more exact results concerning CO2 production rather than only measuring every other percentage. We also could have varied the strains of the yeast to observe how this would have affected CO2 production as well. Another way we could have conducted the experiment concerns the amount of time we let the yeast ferment.

7 Instead of waiting 20 minutes before gathering results, we could have waited different time intervals (10 minutes, 30 minutes, ect.) in order to determine if time had any affect upon CO2 production. In other experiments conducted to research the Fermentation of yeast, a carbon dioxide sensor was used to determine the CO2 Concentration over time (Kulp & Lorenz, 2003). I feel as if an instrument that is used specifically to measure CO2 production may Fermentation lab report 5 have produced more accurate results than simply using a ruler to measure the changes in volume before and after Fermentation . REFERENCES Audesirk, G., and T. Audesirk and Beyers. (2005). Biology: Life on Earth with Physiology, 9th ed.

8 Pearson Benjamin Cummings, San Francisco. Buikema, , and Sarmadi. (2012). Fermentation . Laboratory Manual: Introductory Biology, Hayden-McNeil Publishing, Plymouth, MI. Kulp. K., and Lorenz. (2003). Handbook of Dough Fermentations, 1st ed. Marcel Dekker, New York, NY. Fermentation lab report 6 Figure 1. Change in volume (cm.) in response to different Alcohol concentrations. Series 1- Trial 1 Series 2- Trial 2 8% 12% 14% 16% 8% 12% 0 1 2 3 4 Change in Volume (cm.) Percent Alcohol Amount of Volume Displaced in Different Alcohol Concentrations Series1 Series2