Name ____________________
Mrs. Ross
Root Beer Fermentation Lab
Regents Biology
Anaerobic Fermentation of Sucrose: Root Beer Lab*
Introduction: Cellular respiration is a process that provides chemical energy (ATP) for
an organism by breaking down glucose. If oxygen is available, the process is aerobic and
the ATP production per molecule of glucose is much greater than in the absence of
oxygen (anaerobic).
An anaerobic process called fermentation happens in cells when they break down glucose
without oxygen. There are two types of fermentation. Lactic acid fermentation occurs in
muscle cells when they are oxygen deprived, & alcoholic fermentation, which is involved
in making many foods.
Yeast cells (universal eukaryote & a fungus) obtain energy from glucose through
alcoholic fermentation. When yeast break down glucose, pyruvic acid is converted to
CO2, ethanol, & ATP. The CO2 provides the carbonation in fermented beverages such as
root beer, hence the term “carbonation”.
Root beer was made by our ancestors by soaking Sassafras (a type of tree) root in water,
& adding sugar & yeast. In the early 1900s however, scientists discovered that safrole, a
chemical found in Sassafras root was a carcinogen & human consumption was banned.
Now, a mixture of other herbs & spices make up “root beer extract” which is what is now
used to make homemade root beer.
Purpose: To produce carbonated root beer & observe the process of fermentation of
sugar.
Material
Water
Clean empty 2 liter bottles
Brewers yeast
Sucrose
Measuring spoons
root beer extract
beaker
funnel
mixing spoons
Empty 500mL bottles
Procedure:
Directions are measurements for a lab group of 2 people.
1. Measure out 0.25 g of yeast.
2. Measure out 50ml of warm tap water in a graduated cylinder.
3. Mix the 0.25g of yeast with the 50ml of warm tap water in a small beaker & let
allow mixture to sit for 5 minutes.
4. Measure out 4ml of root beer extract in a graduated cylinder.
5. Measure out 110g of sugar.
6. Warm a bottle of spring water in the microwave.
WARNING: YOU WILL ONLY RECEIVE 1 BOTTLE OF SPRING
WATER!! IF YOU HEAT YOUR BOTTLE TOO HIGH OR TOO LONG IT
WILL WARP, YOU WILL NOT GET A BOTTLE OF ROOT BEER &
WILL LOSE CREDIT FOR THE LAB!!!!
7. Pour your warm spring water into an empty 2L bottle using a funnel.
8. Add the root beer extract & sugar to the 2L bottle & swirl to dissolve the sugar.
9. Add the yeast mixture to the 2L bottle & add warm spring water until the bottle is
half full (1L of liquid).
10. Gently swirl the bottle to mix well.
11. Pour your mixture into two 500ml bottles. Close the cap tightly & hold upside
down to check for leaks.
12. Make a label with your first & last name and put the label on the bottle.
13. Observe & describe the appearance of your root beer in the observation table.
14. You will make observations of your root beer for approximately 10 days. The first
4-5 days your root beer will be placed in a warm, dark place. It will then be stored
in a cool, dark place for 5 more days.
15. At the end of 10 days you will place your root beer in the refrigerator.
Refrigeration will stop the fermentation process and kill the yeast.
Be sure to check your bottles every day for tightness. If they get too
pressurized, they will burst.
16. Enjoy your root beer & answer the questions!!
Date
Observations
Summary Questions:
1. Based on your before & after observations, describe how the appearance of the
root beer changed during the fermentation process.
2. Why was the yeast necessary for this experiment?
3. Why was the sucrose necessary for this experiment?
4. Briefly describe what fermentation is & where each of the ingredients you used in
this experiment fits into the process.
5. Write a chemical equation to show the products & reactants for this process.
*Adapted from Anaerobic fermentation of sucrose by Ms. Foglia