UV Light and Yeast Fermentation Rate
Medium
What happens to yeast when you shine ultraviolet light on it during fermentation? UV light kills bacteria, which is why some water filters use it. This project tests whether UV light also slows yeast fermentation. Yeast fermentation is the process where yeast turns sugar into alcohol and carbon dioxide.
You mix yeast into apple juice in a flask on a heating pad. A tube carries gas from the flask into an upside-down water-filled cylinder. You measure how much water the CO2 pushes out every 10 minutes for one hour. Then you repeat the test with a UV lamp shining on the flask.
The UV-exposed yeast produced no gas for the first 20 minutes. After that it fermented at a slower rate. The total CO2 output was about 60 milliliters less than the control.
Hypothesis
The hypothesis is that the UV light will reduce the rate of yeast fermentation, but not eliminate it.
Method & Materials
You will fill a water bath with water, fill a measuring cylinder with water, put plastic wrap over the measuring cylinder, flip the water-filled measuring cylinder over in the water bath, put 100ml of apple juice into a flask, heat the apple juice in the microwave, add 1/4 teaspoon of yeast to the flask, shake the flask to mix the apple juice and yeast, plug in a heating pad, put the flask on the heating pad, slide a stopper into the top of the flask, place a rubber tubing into the water bath, slip a plastic tubing up inside the cylinder, put a straw on the other side of the measuring cylinder to balance it, and watch for CO2 bubbles in the measuring cylinder.
You will need a flask, a measuring cylinder, a water bath, a stopper, a clamp and stand, an UV lamp, a teaspoon of yeast, a 100ml plastic tube, apple juice, a microwave, a heating pad, a pencil, and a paper pad.
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See what’s includedResults
The results showed that the UV light did affect the fermentation rate of the yeast. The amount of displaced water was about 60 milliliters. The water level went down about 30 ml every ten minutes in both the UV light trial and the control test. However, in the UV light trial, the water level didn't change for the first 20 minutes. The rate of bubbles in the UV light was much slower towards the end of the experiment than the control test.
Why do this project?
This science project is interesting because it provides insight into a new way to pasteurize juices.
Also Consider
Variations to consider include using a stronger UV light and doing more trials and averaging the results.
Full project details
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