TEMPERATURE EFFECT ON FERMENTATION

BY: JOSH PITTMAN

GRADE 9

PITTSBURGH CENTRAL CATHOLIC HIGH SCHOOL

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YEAST -There are 1500 different types of yeast discovered.

-Reproduce asexually.

-A single-celled fungus found on fruits and plants.

-Saccharomyces cerivisiae.

-When added to sugar, it releases CO2.

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ETHANOL FERMENTATION

-Sugar is converted into ethanol and carbon dioxide.-C6H12O6 → 2 C2H5OH + 2 CO2

-Oxygen prevents ethanol fermentation. -6 CO2 + 6 H2O ↔ C6H12O6 + 6 O2

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WHAT AFFECTS FERMENTATION?

-Enzymes’ temperature range.

-The speed of the fermentation depends on the temperature range.

-pH level.

-Various biochemical inhibitors.

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PURPOSE

-What temperature does table sugar water ferment best in?

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HYPOTHESIS

Null: Temperature will not have a significant effect on cell respiration of yeast.

Alternative Hypothesis: Temperature will have a significant effect on cell respiration of yeast.

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MATERIALS -Red Star Rapid Rise Saccharomyces cerevisiae

-Distilled water

-Water

- Table Sugar (sucrose)

-Thermometer

-Pipettes

-Ice cubes

-125 mL flasks

-Scale

-Weigh boats

-Graduated cylinders

-Balloons

-Saran Wrap

-Water tubs

-Heating plates

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PROCEDURE 1. 6 tubs of water were prepared at each of the 6 temperatures. For

temperatures over room temperature (30°, 40°, 50°), food heating plates were used to heat the water to the correct temperatures. For temperatures under room temperature (20°, 10°, 5°), ice was used to chill the water.

2. The sugar solution was made. 30 grams of table sugar was mixed with 300 mL of distilled water (10% sugar solution).

3. 32 mL of distilled water and 8 mL of the sugar solution were added to each of the 36 flasks (2% sugar).

4. 3 grams of Red Star rapid rise Cooking Yeast was added to each flask and balloons were immediately affixed to each flask. They were then transferred to the tubs of water: 6 flasks in each tub.

5. The yeast was exposed to the temperatures for 60 minutes.

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PROCEDURE CONTINUED 6. Each balloon was removed from the flask (careful to

prevent any leakage of gas; each balloon was pinched at the neck and twisted off.)

7. A plastic tub was filled with water.

8. Each graduated cylinder was filled with water to the brim and sealed with plastic wrap.

9. The cylinder was inverted and immersed into the water and the plastic wrap removed.

10. The balloon was placed into the water with the mouth placed into the cylinder.

11. The mouth was slowly released and the air was pumped into the graduated cylinder. The volume of gas was then recorded.

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↑ 40°C: 50 minutes in (above)

CO2 collection

process (below) ↓

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RESULTS

0

20

40

60

80

100

120

140

160

180

200

5 10 20 30 40 50

Vo

lum

e o

f C

O2 (

mL

)

Temperatures (°C)

Temperature Effect on Yeast Respiration

P = 2.27 E-11

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DUNNETT’S TEST

Temperature T value Interpretation

5° 9.656 Significant

10° 8.855 Significant

20° 2.54 Not Significant

40° 1.236 Not significant

50° 2.607 Not Significant

T crit. = 3.39Alpha = 0.05

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CONCLUSION

-The null hypothesis that temperature does not affect the yeast’s ability to ferment was rejected for the temperatures 5°and 10°

-The null hypothesis could not be rejected for the temperatures 20°, 40°, and 50°.

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LIMITATIONS AND EXTENSIONS

-Limitations: CO2 could have escaped from the balloons when measuring the CO2 produced.

-Small changes in temperature could vary in the tubs of water.

-Extensions: Variables could change.

•Test different types of carbohydrates.

•Test different types of environments.

•Test different types of yeasts.

•Directly testing the survivorship of the cells to assure viability. (trypan blue exclusion assay)

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REFERENCES

http://www.wisegeek.com/why-does-yeast-make-bread-rise.htm

http://en.wikipedia.org/wiki/Yeast#cite_note-YeastRef1-0

http://en.wikipedia.org/wiki/Fermentation_(biochemistry)

http://www.mrcroft.com/notes/resp/Temp-Fermentation.pdf

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