A Study of Mold Growth
Developers:
Benjamin Edoff, Robin Reilly
Philadelphia School District
Dr. Allen Marks, Deborah G. Fradkin
Rohm and Haas Company
Grade Level:
K through 12
Discipline:
Mycology, Hygiene, Food
Goals:
Upon completion of this lesson, the students will:
- Be introduced to terms associated with fungi.
- Apply the Scientific Method to problem solving.
- Recognize the importance of a control in an experiment.
- Develop data collection methods and observation skills.
- Discuss and develop safe laboratory procedures.
Objectives:
Upon completion of this lesson, the student will be able to:
- Understand where fungi and molds come from.
- Learn how fungi and molds are formed by growing them in the classroom.
- Determine the percentage of fruit juice in a fruit.
- Identify approximately 4 types of mold by color and size.
- Create graphs documenting fungal growth.
Background:
On a warm
afternoon just after Spring break, a group of 2nd graders arrived at
Science class, and began to settle down for their last class of the
day. As they would be dismissed for the day at the end of class, book
bags were in tow, and the children were getting their pencils out. As I
walked by one group, a boy was retrieving his pencil from deep in his
bag, and as he did so, a sandwich in a flip-top baggie tumbled out.
Immediately a chorus of "Euuu", "Yuck", "Disgusting", and "Nasty" went
up, and all the children gathered around to get a look. Apparently the
bologna and cheese sandwich had spent its Spring break in the book bag,
and was covered with several kinds of fungi. Immediately, a flood of
questions followed, and I shelved the lesson plan for the day and we
did a mini-lesson on the event, which led to discussion of germs,
hygiene and food spoilage. It was a rich session, and this series of
experiments grew from that teachable moment. The objective is to expose
common foods which children frequently have for lunch to different
conditions to see what happens.
As elementary
school teachers we always tell students the importance of washing our
hands to prevent transmission of germs and disease. However, the
effects of washing to curtail this transmission are never immediately
apparent to us, other than our hands looking and smelling clean.
Air-born particles and their role are usually not considered.
We live at the
bottom of an ocean of air which contains many different particles, most
invisible to the naked eye. One common type of air-born particle is
called a spore. When spores land on a suitable surface, under the right
conditions, they can germinate to produce molds. There are four common
types of molds. They are green, blue, black, and water molds. Bread
molds are called Rhizopus nigricans.
Molds live on
foods and liquids of animals and other living and non-living objects.
Most molds produce reproductive spores that are very tiny particles.
These spores are in a case or sac called sporangium. Once the spores
mature, this enclosed case opens and the spores spread into the
environment. These spores produce hyphae that are broken down by the
enzymes inside the food or liquid. In effect, the relationship between
the food and the mold is mutually beneficial. The food provides
nourishment to the mold and the mold breaks down the dead, organic
matter present, becoming visible to us as it grows.
The three
necessary conditions for successful mold growth are food, water, and
moderate temperature. When these three conditions are met, molds will
grow. In this experiment the hosts upon which mold will be encouraged
to grow are fruit, bread, and other common lunch foods. Molds need a
temperature of about 80 degrees Fahrenheit (room temperature) to do
best. Adequate moisture must be present for optimum growth. Water is
needed so that the parts of the cell can interact freely. Light also
affects mold growth. Light is not necessary for mold survival. Plants
need light for survival, but unlike plants, molds do not
photosynthesize, or make their own food using energy from the sun. In
fact, molds tend to grow better in the dark, because strong light can
cause them to become dried out, and their spores will not be able to
germinate.
Molds are useful
since they produce several commonly used drugs. Penicillin is a very
famous drug that is derived from molds. A British scientist named
Alexander Fleming discovered it in 1928. While working with bacterium
he noticed that the bacterium around a mold was dying. This resulted in
a new drug called Penicillin that is used to treat bacterial
infections. It is a widely used drug because there are few side effects
compared to those of other drugs. Molds have produced different forms
of penicillin.
Lesson 1 - Handling White Bread under Different Sanitary Conditions and Observing the Effects on Mold Growth
Several options
are available to the teacher for this series of experiments, which are
explained below. However, the need to address safety with the children
must come first.
Under no
circumstances should any child taste any of the foods at any time. When
handling the samples, gloves must be worn, even though most items are
enclosed in bags or foil. While safety glasses are optional, some
spores will become air-born during handling, and to reduce the unlikely
chance of an eye reaction, glasses should be used if available. Have
all students wash their hands at the end of the lesson. When the
experiment is over, simple disposal in a plastic bag using a twist tie
to close it is adequate because none of the materials or molds are
toxic.
Within the
classroom setting, teachers can choose to test as many conditions as
they wish, for the bread, fruit, etc. In each case however, it is
necessary for each group to include a control. For example, a group may
have a set of samples handled by unwashed hands and a set of samples
handled with hands rinsed in water, or a set of samples handled by
unwashed hands and a set handled by hands washed using soap. Teachers
and children are invited to come up with additional conditions or items
consistent with the procedures described below.
Management of the
activities can also be adapted to suit particular needs. It is
suggested that cooperative groups of 4 or 5 children be established,
with groups testing one, two or more conditions each plus a control,
depending on the size and level of the class.
Materials:
4 loaves of sliced white bread | 1 roll of aluminum foil |
1 box of 150 ZiplocTM sandwich bags | 1 roll of paper towels |
1 box of 150 flip top sandwich bags | cardboard box |
1 bottle of antibacterial hand soap | disposable Latex gloves |
1 bar of soap (suggest IvoryTM Soap) | safety glasses |
Clock with a second hand or stop watches | hand lenses |
Procedure:
Children work in groups of 4 or 5:
In order to determine the effects of washing hands before handling bread, the groups will set up four treatment conditions:
- handling bread for 15 seconds with unwashed hands (which serves as a control),
- handling after rinsing with water for 15 seconds,
- handling after washing with soap for 15 seconds, and
- handling after washing with antibacterial soap for 15 seconds.
For the unwashed
hands condition, each child handles a slice for 15 seconds before
passing it on to the next child in the group, who in turn, handles it
for 15 seconds before passing it on. Each student handles each of the
three slices before wrapping one in aluminum foil, placing one in a
flip-top sandwich bag, and one in a sealed Ziploc(tm) bag, together
with a damp paper towel in each (Use the same amount of water on each
paper towel). These three enclosures are those most commonly used by
children who bring their lunches to school.
Next, one or two
groups will rinse their hands in water for 15 seconds, dry them, and
handle a slice of bread for 15 seconds before placing one in the foil,
one in the flip top bag, and one in the Ziploc(tm) bag. The 15-second
rinsing or washing is done before handling each of the three slices.
The other group members will need to fill the roles of timekeeper and
those who assist in labeling and preparing the bags, foil, and paper
towels beforehand. It is important that the person washing touches
nothing but the bread before placing it in its enclosure and then
closing or folding them shut. Furthermore, the other students should
NOT touch the bread at all. Students can take turns washing if desired.
Likewise, other
groups follow the same procedure for hands washed with the bar soap or
with the antibacterial soap. When completed, each group will have
between 6 and 12 enclosed slices of bread, depending on the number of
conditions tested. For example, if a group tests just one condition
plus a control group, they would have 6 test items - 3 slices handled
with unwashed hands, placing 1 wrapped in foil, 1 in a flip top bag,
and 1 in a Ziploc(tm) bag. Then they would do the same with another
three slices after choosing to wash with either water, soap, or
antibacterial soap. If two conditions plus a control group are tested,
there would be 9 test items.
Then, take all of
the slices and put them in a cardboard box (drawer or closet) and close
it so that it remains dark inside. Let them sit undisturbed for one
week.
Finally, children
write up the purpose, generate their own hypotheses, list all materials
used, and record the procedure they used.
Counting and Recording Colonies, Wet/Dark Conditions
Before returning
the bread to each group, review the purpose of the experiment,
hypotheses, and procedures used. It is important at this point to
discuss and review safety procedures, and have the class and teacher
together create the rules to follow in handling the bread. No one
should touch a mold directly. After reviewing the rules, distribute
gloves and safety glasses to each child.
Return the bread
to each group. Have the children group them by placing the handling
conditions horizontally, and the three enclosure conditions vertically
as in Table 1. Table 1 also shows the total number of colonies of the 4
different types of mold that we found on each piece of bread. Table 2
is a replicate table with the mold results removed and separate columns
for each type of mold. Table 2 can be used as a template for teachers
to use when recording results in their classroom.
Table 1 Number of Colonies of Mold For Wet/Dark Condition
Handling Conditions ==> |
Unwashed |
Water |
Antibacterial Soap |
Bar Soap |
Enclosure |
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|
A1 Foil |
81 |
2 |
1 |
23 |
Ziplock TM |
7 |
12 |
5 |
17 |
Flip Top |
55 |
25 |
17 |
34 |
Table 2 Number of Colonies of Mold For____________Condition
Handling ==> |
Unwashed |
Water |
Antibac |
Soap |
Mold ==> |
Blck |
Grn |
Yllw |
Red |
Blck |
Grn |
Yllw |
Red |
Blck |
Grn |
Yllw |
Red |
Blck |
Grn |
Yllw |
Red |
Enclosure |
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A1 Foil |
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Ziplock TM |
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Flip Top |
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Table 3 shows our results for all the mold growth conditions. |
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Table 3 Number of Mold Colonies For All Handling and All Storage Conditions
Number of Colonies of Mold |
Handling ==> |
Unwashed |
Water |
Antibac |
Soap |
Type ==> |
Blck |
Grn |
Yllw |
Red |
Blck |
Grn |
Yllw |
Red |
Blck |
Grn |
Yllw |
Red |
Blck |
Grn |
Yllw |
Red |
Condition |
Storage |
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Wet/Dark |
A1 Foil |
45 |
9 |
27 |
0 |
0 |
2 |
0 |
0 |
0 |
0 |
1 |
0 |
18 |
0 |
5 |
0 |
Ziplock TM |
2 |
0 |
5 |
0 |
0 |
9 |
3 |
0 |
4 |
0 |
1 |
0 |
14 |
0 |
3 |
0 |
Flip Top |
15 |
23 |
11 |
6 |
6 |
16 |
3 |
0 |
5 |
6 |
4 |
2 |
22 |
0 |
9 |
3 |
Wet/Light |
A1 Foil |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
4 |
0 |
0 |
0 |
0 |
7 |
2 |
0 |
4 |
Ziplock TM |
8 |
12 |
5 |
0 |
6 |
15 |
4 |
0 |
2 |
3 |
1 |
0 |
10 |
0 |
4 |
0 |
Flip Top |
21 |
13 |
11 |
0 |
12 |
2 |
6 |
0 |
10 |
4 |
3 |
0 |
9 |
1 |
2 |
1 |
Dry/Dark |
A1 Foil |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
Ziplock TM |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
Flip Top |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
Dry/Light |
A1 Foil |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
Ziplock TM |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
Flip Top |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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The data sheet
above can be used for recording the number and color of colonies
observed. Up to four different colors of colonies may be present:
black, green, yellow/brown, and red. Regardless of size, simply count
the number of colonies, one color at a time, and list them on the data
sheet for each of the conditions. Do not disturb the contents of the
plastic bags - if a mold is growing on the paper towel, include them in
your count. In the case of the foil, it is necessary to turn the bread
as the count is made. Children should be instructed to wear gloves or
use tweezers and only touch the bread at places where no mold is
present. After all groups have finished recording their tallies and
comparing results, collect the bread and return it to its box.
Conduct a class
discussion to share and compare their findings, and ask if there is a
better way to view the results. Introduce the use of a bar graph, and
demonstrate how to display the data graphically. Use a colored marker
or chalk the same color as the mold to make each bar. Review the data
and conduct a class discussion, followed by students writing their
results and conclusions.
Wet/Light Conditions:
Following the
same procedures outlined in Lessons above, classes may conduct this
part separately or simultaneously. In this series, all samples are left
exposed to ambient light for a week. All other conditions remain the
same. Discussion of the effects of light on mold growth can then be
made in comparison with the wet/dark data. You may wish to run a series
with dry conditions as well.
For the wet/dark
conditions, we noted the following by order of most to least colonies
counted. The bread in the flip top bags showed the most mold growth
followed by the aluminum foil and finally the ziploc bags. The flip top
bags had up to four different colors while the foil and the ziploc bags
had the least.
We concluded that
the ziploc bags were the most effective in preventing mold growth
because they did not allow the foods to be exposed to the air. See
Table 3 for a summary of all our results on bread. As mentioned above,
mold growth requires water. As you can see from Table 3, when we tested
bread under dry conditions, very little mold grew. This may be an
instructive addition for teachers to include.
Lesson 2 - Determining Mold Amounts on Whole Fruits
Materials for whole fruits:
These materials are for whole fruits. |
14 "Sun Maid" Raisins | 14 4-oz containers |
7 "Coastal" Strawberries | 14 16-oz containers |
7 "Red Delicious" Apples | 7 8-oz containers |
7 "No Name" Lemons | Five 64 ounce Plastic Jugs |
7 "Bosc" Pears | |
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Solution Preparation Per One Quart of Water (32 fl. ounces)
Add
the following amounts of solutions to one quart of water. The following
Table gives amounts in either grams, cups, or fl. oz. Use whichever
measure is most convenient. |
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Material |
Wt in g |
Volume in cups |
Volume in fl oz |
| |
A. |
Salt |
200 grams |
2/3 cup |
5 1/2 fluid ounces |
B. |
Antibacterial Soap |
300 grams |
1 1/3 cups |
11 fluid ounces |
C. |
Lemon Juice |
300 grams |
1 1/3 cups |
11 fluid ounces |
D. |
Coffee |
13 grams |
1/4 cup |
2 fluid ounces |
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Students should
work in pairs or groups of four for this activity. Teachers may decide
to use these activities separately or simultaneously depending on the
age level of their students. In addition, teachers should not feel
restricted to using the fruits included in our series of experiments.
Activity 1 - Apples
Each group takes
one whole apple and places the apple into a one-pint container. There
should be 7 containers with 7 apples inside. Fill each container with
the following solutions or until the apple floats.
20% Salt in water
30% Lemon Juice in water
30% Antibacterial Soap or Soft Soap
1.3% Instant Coffee
100% HiC Punch
One Container with Nothing in it
One Container with only Water in it
Activity 2 - Pear
Each group takes
one whole pear and places the pear into a one-pint container. There
should be 7 containers with 7 pears inside. Fill each container with
the following solutions in Activity 1 above or until the pear floats.
Activity 3 - Strawberry
Each group takes
one whole strawberry and places the strawberry into a 1/4 pint
container. There should be 7 containers with 7 strawberries inside.
Fill each container with the following solutions in Activity 1 or until
the strawberry floats.
Activity 4 - Raisin
Each group takes
two whole raisins and places the raisins into a 1/4 pint container.
There should be 7 containers with 14 raisins inside. Fill each
container with the following solutions in Activity 1 or until the
raisin float.
Activity 5 - Lemon
Each group takes
one whole lemon and places the lemon into a 1/2 pint container. There
should be 7 containers with 7 lemons inside. Fill each container with
the following solutions in Activity 1 or until the lemon floats.
Note:
- For the water condition fill the container enough so that the fruit can float.
- For the dry condition simply place the fruit inside its respective containers.
Partially cover
each fruit in its container with a lid and store all the containers in
a five-gallon pail with the lid ajar. Add one pint of water to the
bottom of the pail to prevent moisture loss. The lid should be placed
on each pail to allow airflow from outside. After one day, open up the
containers and pour off the water in the containers. Allow mold to grow
for 7 days and then observe the results. Record your results using the
following "YUK" factor ratings:
The "YUK" Factor Scale
O = no mold growth
1 = Little amount of mold (a spec, a dot)
2 = Some mold growth (partially covered fruit)
3 = Lots of mold growth (mostly covered, pretty bad)
Table 4 shows the
results from our evaluation. Table 5 is a blank that can be used as a
template. The data in Table 4 is shown graphically as a bar graph
generated in an Excel spreadsheet.
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Table 4 Yuck Factor for Whole Fruits
Fruit ==> |
Pears |
Apples |
Lemons |
Strawberries |
Raisins |
Total |
Nothing |
1 |
1 |
2 |
3 |
0 |
7 |
Water |
1 |
0 |
3 |
2 |
3 |
9 |
Anti Bac |
1 |
0 |
1 |
3 |
0 |
5 |
Coffee |
2 |
1 |
2 |
2 |
3 |
10 |
Lemon J |
1 |
0 |
1 |
2 |
0 |
4 |
Salt |
1 |
0 |
1 |
2 |
0 |
5 |
Fruit Punch |
1 |
1 |
3 |
3 |
3 |
11 |
Total ==> |
8 |
3 |
13 |
18 |
9 |
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Table 5 Yuck Factor for _________ Fruits
Fruit ==> |
Pears |
Apples |
Lemons |
Strawberries |
Raisins |
Nothing |
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Water |
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Anti Bac |
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Coffee |
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Lemon J |
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Salt |
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Fruit Punch |
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Lesson 3 - Determining Mold Amounts on Cut Fruits
Materials for cut fruits:
These materials are for Cut fruits. |
14 "Sun Maid" Raisins | 7 (1/4) pint containers |
7 "Coastal" Strawberries | 7 (1/4) pint containers |
7 "Red Delicious" Apples | 7 (1) pint containers |
7 "No Name" Lemons | 7 (1/2) pint containers |
7 "Bosc" Pears | 7 (1) pint containers |
Five 64 ounce Plastic Jugs | Cutting knife to cut the fruits |
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Repeat this
activity using the same procedure as in Lesson 2 except cut each fruit
into pieces before putting them into the container. The pieces of the
fruit should be about 1/4 the size of a whole apple, 1/4 the size of a
whole pear, 1/2 the size of 2 raisins, 1/2 the size of a lemon, and 1/2
the size of a strawberry. Use the "Yuk Factor" Scale and the
accompanying data sheet (Table 5) to record your observations. Table 6
shows the results we found for cut fruit. As can be seen by both the
whole and cut fruit experiment, certain fruits (like strawberries) are
more prone to mold and certain solutions (like fruit punch) will
enhance mold growth. Differences between the whole and cut fruit can be
attributed to the skin of the fruit. The solutions that enhance mold
growth do so because they provide food for the mold. Discuss your
findings with your students and try to hypothesize the reason for your
results. This may lead to ideas for further independent study or
individual science projects for your students.
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Table 6 Yuck Factor for Cut Fruits
Fruit ==> |
Pears |
Apples |
Lemons |
Strawberries |
Raisins |
Total |
Nothing |
2 |
1 |
3 |
3 |
0 |
9 |
Water |
2 |
1 |
3 |
3 |
3 |
12 |
Anti Bac |
1 |
1 |
1 |
2 |
0 |
5 |
Coffee |
2 |
3 |
2 |
2 |
0 |
9 |
Lemon J |
0 |
2 |
1 |
0 |
0 |
3 |
Salt |
1 |
2 |
0 |
0 |
0 |
3 |
Fruit Punch |
2 |
2 |
3 |
3 |
3 |
13 |
Total ==> |
8 |
3 |
13 |
18 |
9 |
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pH of the Solutions Used in Soaking Foods
Explain the
concept of pH (see glossary and other texts for reference materials on
pH) to the students. For practice you can measure the pH of the
solutions used to soak the fruit.
he following is a list of the pH of the solutions that were used in this experiment.
1- |
Nothing (As Is) |
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2- |
Lemon Juice |
30% in Water |
pH = 2.3 |
3- |
Fruit Punch (As Is) |
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pH = 3.1 |
4- |
Instant Coffee |
1.3% in Water |
pH = 4.8 |
5- |
Water |
|
pH = 6.6 |
6- |
Salt |
20% in Water |
pH = 6.7 |
7- |
Anti-Bacterial Soap |
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pH = 7.0 |
Sugar Content in Fruits
The following list provides the sugar content1
(in grams) for each of the fruits used in this experiment. We did not
find a correlation between mold growth and sugar content.
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Fruit |
Sugar Content in Grams |
Pear (raw)- 1 med. (166 g) |
17.4 |
Apple (raw)- 1 med. (138 g) |
18.4 |
Lemon (raw)- 1 med. (58 g) |
1.5 |
Strawberries (raw)- 1 cup (149 g) |
8.6 |
Raisins (dried)- 2/3 cup (100 g) |
65.0 |
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1Data
above provided by Lois Wegfahrt, R.D. at PennState College of
Agricultural Sciences, Cooperative Extension Bucks County, Neshaminy
Manor Center (Doylestown, PA)
Lesson 4 - Determining Mold Amounts on Other Lunch Foods
Materials for other lunch foods:
These materials are for other lunch foods. |
7 pieces of bologna about the size of a cracker | 7 four ounce cups |
7 pieces of cheese about the size of a cracker | 7 four ounce cups |
7 potato chips | 7 four ounce cups |
7 vanilla cookies | 7 four ounce cups |
Using the same
seven solutions that we used in Lesson 2 (Determining Mold Amounts on
Whole Fruits), we tested cheese, cookies, potato chips, and bologna in
the same manner.
Partially cover
each whole food in its container with a lid and store all the
containers in a five-gallon pail with the lid ajar. Add one pint of
water to the bottom of the pail to prevent moisture loss. The lid
should be placed on each pail to allow airflow from outside. After one
day, open up the containers and pour off the water in the containers.
Allow mold to grow for 7 days and then observe the results. Table 7
gives the "YUK" factors for our results. Table 8 gives a blank template.
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Table 7 Mold Growth with Various Liquids
Foods ==> |
Cookies |
Pot Chips |
Bologna |
Am Cheese |
Total |
Liquids |
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Nothing |
0 |
0 |
1 |
0 |
1 |
Water |
0 |
1 |
3 |
0 |
4 |
AntiBac Soap |
1 |
1 |
1 |
0 |
3 |
Coffee |
2 |
1 |
3 |
0 |
6 |
Lemon Juice |
3 |
0 |
1 |
0 |
4 |
Salt |
0 |
0 |
0 |
0 |
0 |
Fruit Punch |
2 |
1 |
3 |
0 |
6 |
Total ==> |
8 |
4 |
12 |
0 |
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Table 8 Mold Growth with Various Liquids
Foods ==> |
Cookies |
Pot Chips |
Bologna |
Am Cheese |
Total |
Liquids |
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Nothing |
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Water |
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AntiBac Soap |
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Coffee |
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Lemon Juice |
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Salt |
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Fruit Punch |
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Total ==> |
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We concluded that
the most mold growth were in the foods that were soaked in coffee and
fruit punch. Next came the foods soaked in water and lemon juice.
Finally, the foods soaked in soap and the nothing category had the
least mold growth.
Bologna proved to
be the food which molds like the best. This is probably due to a
consistent moisture content and an adequate source of food for the
molds to grow. Next were the cookies that the molds liked as well.
Potato chips showed some growth but surprisingly, the cheese showed
absolutely none. We concluded that this occurred because the cheese had
preservatives in it.
Lesson 5 - How much fruit juice is there in a piece of fruit?
Materials:
1 "Red Delicious" Apple | Hand Masher |
1 "Bosc Pear" | Mash Strainer |
1 "No Name" Lemon | Cheese Cloth |
1 "Coastal" Strawberry | |
2 "Sun-Maid" Raisins | |
Procedure for Juicing the Fresh Fruit
For the following
fruits (strawberries, pears, lemons, apples, and grapes) we used three
methods. We used a hand strainer, garlic press, and a masher to turn
each of the whole fruit pieces into juice. This procedure was repeated
for each of the above fruits.
- Weigh the fresh fruit and then cut it into small pieces (as needed to press out the juice).
- Using a hand
strainer, or a garlic press, or a potato masher, press the fruit
against the sides of the container until as much of the crushed fruit
comes out as possible.
- Use a cheesecloth to further separate the juice from the fruit.
- Squeeze out the remaining juice by hand.
- Weigh the juice.
- Divide the weight of the juice by the weight of the fruit. Multiply by 100 to get percent.
The following example shows how we determined the weight of the juice in a strawberry.
Weight of a container | 25 grams |
Place strawberry in a container and weigh it | 65 grams |
Weight of the Strawberry | 40 grams |
|
Weigh the container to determine the juice content | 25 grams |
Place juice in a container | 55 grams |
Weight of the juice | 30 grams |
|
% Juice = Weight of the Juice/Weight of the Fruit |
= 30/40 x 100% = 75 % |
After comparing
the three methods of extraction, the potato masher produced the
smallest amount of juice in the fruit. The garlic press was the best
extractor of juice followed closely by the hand strainer. We concluded
that the garlic press applied the most squeezing pressure and was the
most effective. Also, it appears that juice makes up roughly half of
the total weight of the fruit with the exception of the lemons which
are very thick skinned. Expect to find considerable variation from
student to student and different pieces of the same fruit. This is
where averaging is important.
%Fruit Juice in Fruits
|
Hand Strainer |
Garlic Press |
Potato Masher |
Strawberries |
42 |
53 |
35 |
Grapes |
58 |
56 |
47 |
Apples |
44 |
56 |
45 |
Lemons |
15 |
16 |
17 |
Pears |
52 |
44 |
31 |
We determined the pH of the fruit juices, as well. Our results follow:
pH of Fruit Juices Using pH paper and a pH meter:
Juice |
pH Paper ( * ) |
pH |
meter | |
Strawberry - Fresh |
2 |
3.5 |
Grape - Fresh |
3 |
3.7 |
Apple - Fresh |
4 |
4.4 |
Lemon - Fresh |
0 |
2.3 |
Pear - Fresh |
3 |
4.4 |
Raisin - Fresh |
|
|
Old (1 Month in Refrigerator) | |
Strawberry |
2 |
3.3 |
Pear |
4 |
4.4 |
Lemon |
1 |
2.5 |
( * ) J.T. Baker pHIX (pH 0.0-14) Cat No. 4390-01
We found that all
fruit juices in this experiment were acidic. There was no correlation
between the pH of the juice and the mold growth on the fruit.
Investigating the role of fungi in our world.
Students may wish
to look deeper into how molds have affected us. For example, in Social
Studies the Irish potato famine and the exodus of millions to North
America can be examined. Likewise, their role as decomposers in the
ecosystem, sources of pharmaceuticals, and scourge of the gardener can
be investigated.
References:
Heimler, C.H (1989). Focus of Life Science. Merrill Publication, Columbus, OH.
K.J. (1998). How Rapidly Does Mold Spread on Different Types of Bread? Soar.
Law, Kathy (1997). Experiment: Bread Mold?, MAD Scientist Network.
McKane, L. Microbiology-Essentials and Applications. McGraw Publishing Co.
Acknowledgment:
Lois Wegfohrt from Penn State University
Glossary:
control experiment (k'n-trOl'ik-sper''-m'nt) noun
An experiment that isolates the effect of one variable on a system by
holding constant all variables but the one under observation.
fungus (fung'g's) noun
plural fungi (fun'ji, fung'gi) or funguses
Any of numerous eukaryotic organisms of the kingdom Fungi, which lack
chlorophyll and vascular tissue and range in form from a single cell to
a body mass of branched filamentous hyphae that often produce
specialized fruiting bodies. The kingdom includes the yeasts, molds,
smuts, and mushrooms.
[Latin; perhaps akin to Greek spongos, sphongos, sponge.]
hypha (h'f') noun
plural hyphae (-fe)
Any of the threadlike filaments forming the branching fibers of a fungus.
[New Latin, from Greek huphe, web.]
- hy'phal adjective
mold (mOld) noun
1.Any of various fungi that often cause disintegration of organic matter.
2.The growth of such fungi.
verb, intransitive
molded, molding, molds
To become moldy.
[Middle English moulde probably from past participle of moulen, to grow moldy, from Old Norse mygla.]
pH (p'ach') noun
Chemistry.
A measure of the acidity or alkalinity of a solution, numerically equal
to 7 for neutral solutions, increasing with increasing alkalinity and
decreasing with increasing acidity. The pH scale commonly in use ranges
from 0 to 14.
sporangium (sp'-ran'je-'m) noun
plural sporangia (-je-a)
A single-celled or many-celled structure in which spores are produced,
as in fungi, algae, mosses, and ferns. Also called spore case.
[New Latin : spor(o)- + Greek angeion, vessel. See angio-.]
- sporan'gial (-je-l) adjective
spore (sp�r, spor) noun
1.A small, usually single-celled reproductive body that is highly
resistant to desiccation and heat and is capable of growing into a new
organism, produced especially by certain bacteria, fungi, algae, and
nonflowering plants.
2.A dormant, nonreproductive body formed by certain bacteria in response to adverse environmental conditions.
verb, intransitive
spored, sporing, spores
To produce spores.
[Greek spora, seed.]
- spora'ceous (sp'-r'sh's, sp�-, spo-) adjective
solution (so-lu-shen) noun
Abbr. sol., soln.
1.a. A homogeneous mixture of two or more substances, which may be
solids, liquids, gases, or a combination of these. b. The process of
forming such a mixture.
2.The state of being dissolved.
3.a. The method or process of solving a problem. b. The answer to or disposition of a problem.
4.Law. Payment or satisfaction of a claim or debt.
5.The act of separating or breaking up; dissolution.
[Middle English, from Old French, from Latin solutio, solution-, from
solutus past participle of solvere, to loosen. See solute.]
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