Making Root Beer

Subject: Microbiology

Objectives:

  • Students will observe the production of root beer using yeast.
  • Students will learn how the organism’s cell uses carbohydrates (sugars) from food to make energy.
  • Students will be able to describe the difference in production of ATP in aerobic respiration versus anaerobic respiration?

Vocabulary:

Cellular respiration, glycolysis, Krebs Cycle, aerobic respiration, anaerobic respiration, lactic acid fermentation, and alcoholic fermentation

Safety:

Make sure all utensils have been washed with soap. All bottles need to be rinsed with 10% bleach. Wash hands and bleach bench-tops before starting experiment.

Lesson Plan:

Engage:

Have a student volunteer to stand up and their arms out stretched and then gave them weights to hold. Have the student describe how their muscles feel. Fill test tube 4/5 full with warm tap water and add combine package of yeast. Mix well with finger covering opening of tube. Then add a 1/2 package of sugar and covering the opening with small water balloon. Ask the students what compound that is being produced that allows the balloon to expand.

Explore:

Distribute handouts describing the laboratory activity entitled, “Root Beer Fermentation”. Small group of students will carry out the lab activity, data collection, and analysis of the data handout.

Materials:

Clean, empty, 2 L plastic bottle + caps

Funnel

1 cup measuring cup

¼ tsp measuring spoon

1 T. measuring spoon
Water (preferably spring water)
Powdered bakers yeast
Root beer extract (grocery store brand is fine, although
(Zatarain’s, Hires and A&W do sell their version of extract for a
hefty price)
Sugar

Commercial Root Beer (taste control)

Prep Time: 30 min

Total Time: 3 to 4 days
Procedure:
1. Assembly the necessary equipment and supplies.

2. With a funnel, add in sequence:

1 level cup of sugar (May need to adjust to desired sweetness. Cutting the sugar in half still produces adequate carbonation with much less sweetness).

3. Add 1/4 teaspoon of yeast (fresh and active).

4. You can see the yeast granules on top of the sugar.

5. Shake to distribute the yeast grains into the sugar.

6. Swirl the sugar/mixture in the bottom to make it concave (to catch the extract).

7. Add with funnel:

1 T. of root beer extract (I prefer Zatarain’s, but Hines, etc. will work) on top of the dry sugar.

8. The extract sticks to the sugar which will help dissolve the extract in the next steps.

9. Half fill the bottle with fresh cool water (the less chlorine, the better). Rinse in the extract which sticks to the tablespoon and funnel. Swirl to dissolve the ingredients.

10.Fill to the neck of the bottle with cool water, leaving about an inch of head space, securely screw cap down to seal. Invert repeatedly to thoroughly dissolve.

11. Place at room temperature (RT) about 3 to 4 days until the bottle feels hard to squeeze. Move to a cool place (below 65°F).

12. Refrigerate overnight to thoroughly chill before serving. Crack the lid of the cool root beer just a little to release the pressure slowly.

NOTE: Do not leave the finished root beer in a warm place once the bottle feels hard. After a couple of weeks at RT, especially in the summer when the temperature is high, enough pressure may build up to cause the bottle to explode! There is no danger if the bottle is refrigerated.

Explain:

Respiration: The breakdown of sugar (glucose) to form ATP (a form of energy
for an organism). There are two types, aerobic and anaerobic (also called
fermentation).

History of Root Beer: Root beer was made by our fore fathers by soaking
Sassafras (a type of tree) root in water, and adding sugar and yeast (yeast
for carbonation). In the early 1900's however, scientists discovered that
safrole, a chemical found in Sassafras root, was a carcinogen (which means
it is a cancer causing agent.) Now, a mixture of other herbs and spices makes
up "root beer extract" which is what we now use to make homemade root beer.

Background Information: There are two types of respiration: aerobic (requiring
oxygen) and anaerobic (without oxygen). 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, which
is involved in the making of food products. 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. Fermentation is used to make a variety of food
products, including the making of beer, wine, bread, cheese, sauerkraut, and baked
goods. It is the carbon dioxide produced by the yeasts that give root beer its "fizz."
This fizz is produced in store bought root beer by a carbonation machine that forces
carbon dioxide into the root beer mixture, without the aid of yeast.

General Equation for alcoholic respiration:

C6H12O6(glucose)+ yeast  2CO2 +2 CH3CH2OH (alcohol) + 2 ATP (energy)

Now we can explain the process that the body goes through to produce the lactic acid that they felt when holding the weights as well as how the CO2 and alcohol is produced through the root beer experiment.

Elaborate:

Discuss how fermentation is important in production of many products. Cheese, buttermilk, sauerkraut, yogurt, etc are made through lactic acid fermentation. Beer, bread, root beer, etc. are made by alcohol fermentation.

Evaluate:
Students will complete a data chart and questions.

Questions:
1. What is fermentation?

2. Why was the sugar necessary? It is possible to produce a low-calorie root beer using this method? Why?

3. Why were the yeasts necessary in this experiment?
4. What would happen if you resuspended the yeast in hotter or colder water? Why?

5. List the needed ingredients to make root beer.

6. Explain how commercial (store bought) root beer is carbonated.

7. Explain how homemade root beer will be carbonated.

Resources:

Fankhauser, D. Root Beer: How to make it at home.U.C.ClermontCollege. 1996.

Microbiology in Food Systems: Root Beer Production. Institute of Food Technologists.