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Yeast Science Fair Project

Grape Sugar Fermentation by Yeast

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Grape Sugar Fermentation by Yeast | Science Fair Projects | STEM Projects
What happens when yeast runs out of oxygen but still has sugar to eat? It switches to fermentation. That process produces alcohol and carbon dioxide instead of using oxygen. You place dried baker's yeast in a sealed plastic bag. Inside a second perforated bag, you crush 150 grams of grapes to release the juice. The juice mixes with the yeast. A pH strip taped inside tracks acidity changes. Over the next hour, gas fills the bag and foam appears. You test the gas with a glowing splint. Carbon dioxide snuffs it out. The pH drops as the juice turns more acidic. Leave the bag open for a few days and bacteria convert the alcohol to vinegar.

Hypothesis

The hypothesis is that yeast will use grape sugar as a substrate for cellular respiration, resulting in the production of carbon dioxide and ethanol.

Method & Materials

You will use two plastic baggies, yeast, and grapes to observe the results of cellular respiration of yeasts, using grape sugar as a substrate and yielding carbon dioxide and ethanol.
You will need two self-locking plastic baggies, one which has perforations, a heavy-duty freezer bag, 5 grams of dried bakers yeast, a pH indicator strip, and 150 g of grapes.

Results

The experiment showed that yeast can use grape sugar as a substrate for cellular respiration, resulting in the production of carbon dioxide and ethanol. The most interesting observation was that the carbon dioxide gas produced extinguished the splint.

Why do this project?

This science project is interesting and unique because it demonstrates the process of fermentation, which is used to make many different types of alcoholic beverages.

Also Consider

Experiment variations to consider include testing different temperatures to determine the best temperature for yeast enzyme activity, and allowing air to reach the juice after a few days to observe the conversion of alcohol to acetic acid due to bacterial action.

Full project details

Additional information and source material for this project are available below.

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