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## The Effect of Yeast on Different Fruit Juices

Researched by Kristyn S.
2001-02

PURPOSE

The purpose of this experiment was to determine the amount of fermentation of four different fruit juices after adding yeast.

I became interested in this idea when I saw the fruit in my family’s refrigerator starting to ferment.

The information gained from this experiment may be used by wineries to determine which fruit juice ferments best.

HYPOTHESIS

My hypothesis is that the fruit juice with a higher percentage of sugar will produce more fermentation.

I base my hypothesis on the World Book Encyclopedia, which states,
"Yeast breaks down sugar obtained from fruit juice into ethyl alcohol and carbon dioxide gas for use in wine."

EXPERIMENT DESIGN

The constants in this study were:

• The temperature.
• The amount of juice (250ml).
• The amount of yeast (1g)
• Size and shape of container
• Time allowed to ferment.
• Method of measurement.

The manipulated variable was the type of fruit juice.

The responding variable was the amount of fermentation as shown by the reduction of sugar.

To measure the responding variable I used a brix meter to find the percentage of sugar before and after fermentation for each sample to calculate the difference.

MATERIALS

 QUANTITY ITEM DESCRIPTION 1 Brix meter 16 Transparent containers 12g Yeast 25000ml Orange juice 1250ml Apple juice 1250ml Cranberry-grape juice 1 Cylinder 1 Gram scale 1 Thermometer

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PROCEDURES

1. Gather materials.
2. Label four containers OJ control 1,2,3 and 4.
3. Label four containers as oj1, oj2, oj3, and oj4.
4. Label four containers as ap1, ap2, ap3, and ap4.
5. Label four containers as cgr1, cgr2, cgr3, and cgr4.
6. Add 250ml of orange juice to each of the containers labeled OJ control 1,2,3 and 4.
7. Add 250ml of orange juice to each of the containers labeled OJ 1,2,3 and 4.
8. Add 250ml of apple juice to each of the containers labeled AP 1,2,3 and 4.
9. Add 250ml of cranberry-grape juice to each of the containers labeled cgr 1,2,3 and4.
10. Measure the sugar in each of the juices before adding the yeast, record results.
11. Add one gram of yeast to each of the containers labeled OJ 1,2,3, and 4.
12. Add one gram of yeast to each of the containers labeled AP 1,2,3, and4.
13. Add one gram of yeast to each of the containers labeled cgr 1,2,3, and4.
14. Allow the juice to ferment for 72 hours.
15. Use the brix meter to measure the sugar after the fermentation process, record results.
16. Subtract first measurement from the second measurement, record results
17. Compare which fruit juice produced the most fermentation, record results.

Results

The original purpose of this experiment was to determine the amount of fermentation of 3 different fruit juices after adding a certain amount of yeast.

The results of this experiment were that the orange juice produced the most fermentation. Also the orange juice turned foamy on the surface. On the bottom of each container for each sample a "gooey" substance formed. The apple and cranberry-grape juice turned murky from the yeast and after a while bubbles formed on the surface.

Conclusion

My hypothesis was that fruit juices with a higher percentage of sugar would produce more fermentation.

The results indicate that this hypothesis should be accepted, because the orange juice, which had the highest sugar content, produced the most fermentation.

Because of the results of this experiment, I wonder if using more yeast wold produce more fermentation or if using another type of juice with two of them mixed together like the cranberry-grape juice, would produce less fermentation.

My findings should be useful to wineries because I found that the juices I used produced a large amount of fermentation therefore might make good wine.

If I were to conduct this project again I would do more trials, do a replication of the entire experiment, use more varieties of juices and use a better method of measurement .

ACKNOWLEDGEMENTS

I would like to thank the following people. Without their help, my project would not have been possible.
* My dad for transporting me to Tree Top to pick up a tool I needed for my experiment, buying me the supplies I needed for my experiment and picking me up after school from SOAR.
* John Baranowski of Tree Top for lending me that  tool and explaining how to use it.
* My sister Kaity for taking pictures of my experiment.
* My mom for helping me to make things better.
* Mrs. Helms for helping me with my display and showing me how to do things.
* Mr. Newkirk for always helping me with everything that has to do with my science project.

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