TEACHER
ACTIVITY GUIDE
Root Beer Production
EXPECTED
OUTCOMES
This
activity will allow students an opportunity to explore yeast fermentation by
producing old-fashioned root beer.
ACTIVITY
OBJECTIVE
This
experiment will illustrate to the student that fermentation processes, as in
yeast fermentation, can be used to produce a naturally carbonated beverage.
ACTIVITY
LENGTH
Approximately
30 minutes for setup and 1-2 weeks to conduct.
SCIENTIFIC
PRINCIPLES
Traditional
root beer was naturally carbonated by the action of yeast. This action is
known as fermentation, a process that converts sugars into alcohol and carbon
dioxide.
MATERIALS
REQUIRED
2,
3, or 4-liter plastic container for food
1
package of baker's yeast
Root
beer flavoring extract, 15-20 mL
Sugar
Warm
tap water (37oC)
6-8
plastic, 2-L soft drink bottles with caps
5%
bleach rinse to clean bottles
Stirring
spoons
Balance
Permanent
marker
TABLE 1
|
Root
Beer (L)
|
Yeast
(g)
|
Sugar
(g)
|
|
2
|
0.325
|
227.0
|
|
3
|
0.49
|
340.5
|
|
4
|
0.65
|
454.0
|
STUDENT EXPERIMENTAL PROCEDURE
1.
Dissolve
yeast in 250 mL of warm water (37oC). Let this mixture stand for 5
minutes or longer. See Table 1 for appropriate quantity of yeast.
2.
With the permanent marker, mark the container at the desired level
where 2, 3, or 4 L of liquid would be.
3.
In the plastic container, combine root beer extract and sugar with
sufficient warm water (37oC) to dissolve the sugar (approximately 2
cups). See Table 1 for appropriate quantities of sugar. Use 10-30 mL of
extract, depending on your personal taste preference for root beer flavor.
Refrigerate the leftover extract.
4.
Taste for overall flavor. Add more sugar or root beer extract to suit
your taste. [Samples prepared for UD workshop are not for consumption.]
5.
Add the yeast mixture. Make sure that the yeast is suspended completely
before adding it. Mix thoroughly.
6.
Add additional warm water to bring the level to within 8 cm of the top
of the container.
7.
Wash the soft drink bottles well with detergent and hot water. Rinse
with a 5% bleach solution to sanitize. Rinse several times with warm water.
8.
Fill
bottles with root beer up to 2.5‑5 cm from the top. Tightly secure the
caps on the bottles. Lay bottles on their side to check for leaks. Reseal
bottles that show signs of leakage. Bottles not sealed properly may become
flat or sour.
TEACHING TIPS
·
Brewing
yeast can be purchased from a local home brewing store or hobby store.
Ale yeasts are the best. Champagne
yeasts can be used but tend to cause too much carbonation and internal
pressure. Root beer extract can be purchased at the grocery store or
home brew store.
·
Use
containers that are specifically for food.
Chemical containers, although they may look clean, may still have
chemical residues on them. Emphasize the proper water temperature (warm) for
C02 development.
·
If the
yeast mixture is not mixed correctly, the
carbonation process will be impeded and the end product will not have the
proper amount of carbonation.
·
Too
much sugar can be detrimental to proper yeast growth.
·
5% v/v
bleach rinse is made by adding 5 mL, of bleach to 95 mL of water.
Emphasize good cleaning and rinsing of the bottles and caps.
·
Fill
only to 1-2 inches from the top. Bottles
filled too full won't allow enough expansion for the gas. Bottles filled too
low will give too much headspace above the liquid, and the gas will escape
from the liquid into that area.
·
Store
the bottles in the refrigerator for only 1-1.5 weeks past the processing time.
Although refrigeration slows the fermentation process, it doesn't stop it
completely.
·
Yeast-carbonated
root beer will contain some alcohol. However, it would take 100 root beers to
equal the amount of alcohol in one beer!
·
Plastic
soft drink bottles are less dangerous than glass bottles. The pieces of an
exploded plastic bottle do less damage than pieces of an exploded glass
bottle. Also, plastic containers
can be squeezed to determine the internal pressure.
QUESTIONS
& ANSWERS
1.
Why should brewing yeast be used rather
than the yeast used to make bread?
Ans.
There are many strains of yeast. As yeasts carry out their metabolic function,
they produce flavors that are incorporated into the product. Each product is
characteristic of the flavor and odor of these different strains. For example,
it would be undesirable to have a "bready " flavor and odor in
the root beer. This would occur if common baker's yeast is used
2.
When suspending the yeast, you were to use warm water (37oC).
What would happen if hotter or colder water is used? Why?
Ans.
Appropriate water temperature not only improves the ability of the yeast to
soften and dissolve but is essential in providing the necessary conditions for
proper yeast activity. Water that is too cold inhibits and slows the process,
whereas water that is too hot could kill the yeast or interfere with optimal
fermentation. The end product in either case will be a product with little or no carbonation
3.
What is the purpose of sugar in the formula?
Ans.
Because yeasts are unable to produce
their own energy through photosynthesis, they require a carbon source. Sugar
serves as this source. Because excess sugar is put into the formula, there is
enough for the fermentation process as well as extra for sweetening.
4.
Is it possible to produce a low-calorie root
beer using this method? Why?
Ans.
(Using minimal amounts of sugar will supply the necessary amount of food the
yeast will need. The sugar will be nearly or totally consumed by the yeast
during the fermentation process, leaving little or no sugar left to contribute
to the caloric content. An artificial sweetener can be added to increase the
sweetness but cannot be used to replace the sugar, since the bacteria cannot
use artificial sweeteners as a food source.
5.
What is the natural carbonation process? How are soft drinks carbonated artificially?
Ans.
As the yeast consumes the sugars during the incubation or processing time, it
converts them into C02 and alcohol. Soft drinks are carbonated
artificially by direct charging of the beverage with pressurized or bottled
carbon dioxide.
6.
Compare the sensory quality of the homemade root beer with commercially
produced root beer.
Ans.
Any answer is acceptable here.
STUDENT ACTIVITY GUIDE
Root Beer
Production
ACTIVITY
OBJECTIVE
This experiment will illustrate that fermentation
processes, as in yeast fermentation, can be used to produce a naturally
carbonated beverage.
BACKGROUND INFORMATION
Traditional root beer was naturally carbonated by the
action of yeast. This action is known as fermentation, a process that converts
sugars into alcohol and carbon dioxide.
MATERIALS REQUIRED
2,
3, or 4-L plastic container for food
1 package of baker's yeast
Root
beer flavoring extract, 15-20 mL,
Sugar
Warm tap water (37oC)
6-8 plastic, 2-L soft drink bottles with caps
5%
bleach rinse to clean bottles
Stirring spoons
Balance
Permanent marker
PROCEDURES TABLE
1
|
Root
Beer (L)
|
Yeast
(g)
|
Sugar
(g)
|
|
2
|
0.325
|
227.0
|
|
3
|
0.49
|
340.5
|
|
4
|
0.65
|
454.0
|
EXPERIMENTAL PROCEDURE
1.
Dissolve
yeast in 250 mL of warm water (37oC). See Table 1 for appropriate quantity of yeast. Let this
mixture stand for 5 minutes or longer.
2.
With
the permanent marker, mark the plastic container at the desired level where 2,
3, or 4 L of liquid would be.
3.
In the
plastic container, combine root beer extract and sugar with sufficient warm
water (37oC) to dissolve the sugar (approximately 2 cups). See
Table 1 for appropriate amount of sugar. Use 10-30 mL of extract, depending on
your personal taste preference for root beer flavor. Refrigerate the leftover
extract.
4.
Taste for overall flavor. Add more sugar or root beer extract to suit
your taste.
5.
Add the yeast mixture. Make sure that the yeast is suspended completely
before adding it. Mix thoroughly.
6.
Add additional warm water to bring the level to within 8 cm of the top
of the container. Wash the soft
drink bottles well with detergent and hot water. Rinse with a 5% bleach
solution to sanitize. Finally, rinse several times with warm water.
7.
Fill bottles
with the root beer formula, up to 2.5-5 cm from the top. Tightly secure the
caps on the bottles. Lay bottles on their side to check for leaks. Reseal
bottles that show signs of leakage. Bottles not sealed properly may become
flat or sour.
QUESTIONS
1.
Why
should "special" yeast be used rather than the yeast used to make
bread?
2.
When
suspending the yeast, you were to use warm water (37oC). What would
happen if hotter or colder water is used? Why?
3.
What is the purpose of sugar in the formula?
4.
Is it possible to produce a low-calorie root beer using this method?
5.
What is the natural carbonation process? How are soft drinks carbonated
artificially?
6.
Compare
the sensory quality of the homemade root beer with commercially produced root
beer.
