Name:__________________________________ Period:________ Date:____________
Root Beer Lab: Demonstration of Fermentation!
Cellular Respiration:
The breakdown of sugar (glucose) to form ATP ( the form of energy
cells can use organism). There are two types of cellular respiration:
aerobic and anaerobic (also called fermentation).
History of Root Beer: Root beer was made by our ancestors by soaking
Sassafras (a type of tree) root in water, and adding sugar and yeast (for
carbonation). In the early 1900 however, scientists discovered that safrole, a
chemical found Sassafras root, was a carcinogen (cancer-causing agent) and human
consumption has been banned. Now, a mixture of other herbs and spices makes up
“root beer extract” which is what is now used to make homemade root beer.
Background Information:
There are two types of cellular respiration:
aerobic (requiring oxygen) and anaerobic (without oxygen.)
Aerobic Respiration is more efficient in that it produces 38 ATP Molecules for every glucose molecule that
is broken down.
Anaerobic Respiration is much less efficient in that it produces only 2ATP Molecules of ATP for eery
glucose molecule that is broken down.
Anaerobic Respiration
Yeast cells (a type of fungus) obtain energy from glucose (sugar) by a specific anaerobic process called
fermentation. There are two types of fermentation, lactic acid fermentation (which occurs in muscle cells when
they are oxygen deprived), and alcoholic fermentation. Alcohol fermentation is involved in the making a variety
of food products including bread, cheese, beer, wine and sauerkraut.
Alcoholic fermentation begins after glucose diffuses into the yeast cell. The glucose is broken down into 2, 3
carbon molecules called pyruvic acid. The pyruvic acid is then converted to CO2, ethanol, and energy for the
yeast cell. Don't get excited, students, there is very little ethanol in this root beer. Yeast is used to make bread
and the “air holes” are actually the result of little pockets of CO2 (think of lots of little warm CO2 balloons) that
Yeast double its population in
about two hours through the process of budding (asexual reproduction)
the yeast produce during cellular respiration that makes the dough rise.
It is the carbon dioxide produced by the yeasts that will give our root beer its "fizz." The fizz in store bought
root beer is made using a carbonation machine that forces carbon dioxide into the root beer mixture, without the
aid of our little yeast friends.
C6H12O6 ====> 2(CH3CH2OH) + 2(CO2) + Energy (which is stored in ATP)
Sugar
Alcohol
Carbon dioxide gas
(Glucose)
(Ethyl alcohol)
Purpose: To produce a gallon of root beer by the Fermentation of sugar.
Materials:
-Large beaker for mixing
-Water
-Bakers yeast (the dry kind)
-Root beer extract
-Sugar
- Measuring cups
-Wooden spoon
-2 Liter bottle with cap
-Funnel
-Timer
Procedure:
1.
Dissolve 1/2 mL of Yeast in 150 mL of very warm water.
2.
Let stand for 5 minutes. Being in warm water activates the yeasts, and wakes them up from being
dried out.
Begin step 4 while waiting the 5 minutes.
In the large beaker, fill about half way up with water, combine 1 ½ tablespoons of root beer extract with
about 267 mL of sugar, warm the mixture to dissolve the sugar. Gently stir while the mixture is heating.
When 5 minutes has passed (from step 2) add the two mixures to the 2 liter bottle and add warm water to
bring the level of the liquid up to two liters (be sure to use very warm water).
Securely place cap on two Liter bottle and place in the cabinets next to the sinks.
3.
4.
5.
6.
We cannot drink the root beer for one whole week because…
Homemade root beer must be aged for 3 or 4 days in a warm, dark place. Then it must be stored in a
cool dark place for 2 more days. Refrigeration will stop the fermentation process and kill the yeast.
Day #1 Lab Discussion:
1. Describe the appearance of the root beer before the fermentation process.
2. Why were the yeast necessary in this experiment?
3. Why was the sugar necessary in this experiment?
4. Why did we heat the water?
5. What is the yeast trying to do with the sugar?
6. Why do we have to leave the bottle for a week before we drink it?
7. Why do we want the CO2 to collect in the bottle?
8. Could we survive using this same process? If not, why not?
Name: ___________________________ Date: ___________________Period:_________
Post Lab Questions (When the root beer is ready)
1. Describe the appearance of the root beer after fermentation. Does it look different from
the way it looked on day #1? If so, how?
__________________________________________________________________________________________
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2. Carefully open the bottle. Was the bottle under pressure? Was there any carbonation? If there was
carbonation, explain how the root beer came to be carbonated.
7. **What is safrole? Why do we not use it anymore?
8. **List the needed ingredients to make root beer.
9. Why did we put the yeasts in the warm water for 5 minutes?
10. **What is fermentation?