One of the main products of fermentation which has had an incredibly important role through human history is wine, and it has become a topic of my own interest for different reasons I mentioned within the following extended essay. There is a surprisingly large number of varieties of wine, but the two most common are red wine and white wine. They both come from same genus of grape, vitis, but they have different alcohol graduation, where red wines have an average percentage alcohol of 12º to 14º and white wines 10º to 12º. If the percentage alcohol in a fermented liquid depends on the microorganisms that have fermented it, this leads to the following question: To what extent does the type of grape, red or white, affect the growth rate and therefore the growth curve of leavening agents?
Colorimetry is commonly used in microbiology in order to determine the turbidity of a liquid. This allows quantification of the number of microorganisms in it. A colorimeter was used to measure the turbidity of grape juices inoculated with bakers yeast at specific time intervals over the course of a week. This was used to calculate the population growth curves of the microorganisms in the different samples. The population growth curves obtained of the red and white grape juice samples showed an statistically significant difference which was calculated through a paired T-Test.
A trend was present in all the populations of white grape juices. They started declining before the red grape juices populations, suggesting that there are less sugars in the white grapes than in the red grapes and therefore less alcohol can be formed by the yeast, leading to the conclusion that this may be one of the reasons why the alcohol graduation is lower for white than red wine.
Link to my Extended Essay:
https://www.scribd.com/document/325372393/Biology-Extended-Essay-Final-Draft
