Caloric Content of Food
Hands-On Labs, Inc.
Version 42-0143-00-02
Review the safety materials and wear goggles when
working with chemicals. Read the entire exercise
before you begin. Take time to organize the materials
you will need and set aside a safe work space in
which to complete the exercise.
Experiment Summary:
You will describe a calorimeter. You will also compare
and contrast carbohydrates, lipids, and proteins for
energy utilization in the human body. You will create
a calorimeter to determine the energy content of
three different foods, and compare their findings
to the estimates found on nutrition labels. Finally,
you will calculate the amount of estimated energy
content of the three foods by using Atwater factors.
EXPERIMENT
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Learning Objectives
Upon completion of this laboratory, you will be able to:
● Define calorie, kilocalorie, dietary calorie, and specific heat capacity of water.
● Describe a calorimeter.
● Describe carbohydrates, lipids, and proteins for energy utilization in the human body.
● Describe Atwater factors.
● Create a rudimentary calorimeter and use it to determine the energy content of three foods.
● Calculate the percent difference of the estimated energy content of the food between the
output of the calorimeter and the estimated energy content of the food as listed on a nutrition
label.
● Calculate the estimated caloric content of foods based on Atwater factors.
Time Allocation: 2 hours
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Experiment Caloric Content of Food
Materials
Student Supplied Materials
Quantity Item Description
1 Aluminum pie pan
1 Aluminum foil
1 Bottle of distilled water
1 Dish soap
1 Food item of choice (examples include potato chips or popcorn)
1 Lighter OR matches and a candle
1 Marshmallow
1 Nut (pecan, almond, walnut, or other)
1 Roll of paper towels
1 Source of tap water
HOL Supplied Materials
Quantity Item Description
2 Aluminum cups, 2 oz
1 Burner stand
1 Digital scale, precision
1 Glass beaker, 100 mL
1 Pair of safety goggles
1 Test tube clamp
1 Thermometer
Note: To fully and accurately complete all lab exercises, you will need access to:
1. A computer to upload digital camera images.
2. Basic photo editing software such as Microsoft Word® or PowerPoint®, to add labels, leader
lines, or text to digital photos.
3. Subject-specific textbook or appropriate reference resources from lecture content or other
suggested resources.
Note: The packaging and/or materials in this LabPaq kit may differ slightly from that which is listed
above. For an exact listing of materials, refer to the Contents List included in your LabPaq kit.
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Experiment Caloric Content of Food
Background
Calorimeter
A calorie (cal) is a unit of energy. It represents the amount of heat necessary to raise the
temperature of one gram of water by one degree Celsius (°C) which is also called the specific heat
of water. Therefore, the specific heat of water (C
water
) is:
When measuring with calories, the term “dietary Calorie” (with the capital C) represents a
kilocalorie (kcal) or 1000 calories. In order to determine the amount of energy that is stored in
a substance, a calorimeter is used. A calorimeter is a tool that is used to measure heat that is
released from chemical reactions.
There are different types of calorimeters, but a specific type of calorimeter, called a bomb
calorimeter, is often used in measuring the caloric content of a substance. A bomb calorimeter
is used to measure energy changes in reactions that occur in a constant volume. Within a bomb
calorimeter, a “bomb” is a chamber that holds the reactants that are measured. The bomb is
immersed in an insulated bath of a known quantity of water. Reactants begin a reaction because
they are ignited within the bomb using an electrical wire. The heat that is produced from the
reaction is absorbed by the surrounding water. The temperature of the water is taken before and
after the reaction. Knowing the heat capacity of the calorimeter (including the bomb and water)
and the final temperature of the system, the amount of heat that was released by the chemical
reaction can be calculated. See Figure 1.
Figure 1. Pictorial representation of a bomb calorimeter.
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Experiment Caloric Content of Food
Carbohydrates, Lipids, and Proteins
Humans obtain the energy required for biological processes from eating food. The energy
contained in the chemical bonds of the food is released when that food is oxidized (combined
with oxygen) and products are formed in an exothermic chemical reaction. While some of the
energy stored in the food is released as heat, some of it is also stored in other chemical bonds,
such as in the formation of adenosine triphosphate (ATP). The energy released from foods is
measured as dietary Calories, or kilocalories.
Carbohydrates, lipids, and proteins are the three main groups of large molecules (macromolecules)
that are used for energy in food. Each type of the three main groups has an important function in
the human body. Food labels typically include information about carbohydrates, fats and proteins,
all of which can be used by the human body for energy as well as other functions. The differences
in the elemental composition and molecular structures of these biological molecules results in
different amounts of energy released per gram of carbohydrate, protein or fat. In addition, the
human body utilizes these substances in different ways. Carbohydrates and fats are both very
important for energy metabolism. However, under normal conditions, proteins are not likely to
be used for energy because their component amino acids are more likely to be used to build the
body’s own proteins.
Carbohydrates, found in foods from plant sources, include simple sugars, starches and fiber. The
smallest unit of a carbohydrate is a simple sugar, also called a saccharide. A monosaccharide is one
saccharide molecule, the smallest building block of a sugar. See Figure 2. Most monosaccharide
molecules have the chemical formula C
n
(H
2
O)
n
, a “carbon-hydrate,” where “n” is three or greater.
The human body can utilize carbohydrates as the quickest form of energy in the body because it
is easily broken down into usable energy. Because of it’s chemical structure, fiber (another form
of carbohydrate) cannot easily be oxidized in the body because humans do not have appropriate
enzymes that can cause fiber molecules to react with oxygen.
Figure 2. The molecular structure of the monosaccharide fructose, C
6
H
12
O
6
(left) and glucose,
C
6
H
12
O
6
(right).
Lipids (fats) are composed of large molecules that include triglycerides (saturated and unsaturated
fats) which are long chains of linked carbons that have a glycerol backbone and three fatty acids.
See Figure 3. Like carbohydrates, fats are also composed of carbon, hydrogen, and oxygen. The
many bonds in the long chains of molecules such as fatty acids give fats a high amount of stored
energy (high amount of calories). Though the amount of energy obtained from fats is high,
breaking down the molecules for use of energy in the body takes more time than carbohydrates.
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Experiment Caloric Content of Food
Figure 3. The molecular structure of a triglyceride. The glycerol backbone is shown in red.
Proteins are composed of hundreds of small molecules called amino acids, which are linked
together through peptide bonds to form very large molecules, in much the same way that many
monomer sugar molecules, such as glucose, combine to form larger molecules, such as starch
and fiber. There are 20 different types of amino acids that can be found in proteins, all of which
contain an amino group, a carboxylic acid group and a variable component called an R group, as
shown in Figure 4. Like carbohydrates and fats, amino acids contain C, H and O. However, unlike
carbohydrates and fats, proteins also contain nitrogen (N). In general, the proteins consumed
from food are broken down into amino acids but are not further broken down to release energy.
Instead, these amino acids are used to build the body’s own proteins and nucleic acids, which
require the nitrogen found in proteins.
Figure 4. The basic structure of an amino acid includes an alpha carbon (black), alpha hydrogen
(orange), an amino group (blue), a carboxyl group (red), and an “R” group, or side chain (purple)
which varies among different amino acids.
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Experiment Caloric Content of Food
Atwater Factors
Each type of molecule releases a different amount of energy when it undergoes chemical reactions
in the body. Atwater factors were developed from research studies that used a bomb calorimeter
to determine the average amount of Calories from each type of macromolecule in food (per
gram). Food industries can use Atwater factors to determine the approximate amount of Calories
in foods without actually putting them into a bomb calorimeter.
The following are Atwater factors:
● Carbohydrates produce approximately 4 Calories per gram (when determining the amount
of usable carbohydrates in a food, subtract the amount of fiber per gram since the body
cannot break it down).
● Proteins produce approximately 4 Calories per gram.
● Fats provide approximately 9 Calories per gram.
When food industries use Atwater factors to determine the approximate amount of Calories
in a specific amount of food, they subtract out the amount of Calories from fiber (from the
carbohydrate amounts) and other indigestible portions of the food. Because these factors are
estimates, and because the food industries can round downward, caloric values on nutritional
labels and nutritional menus are often not correct.
Experiment Calculations
In this experiment, you will attempt to mimic a rudimentary calorimeter in order to determine
the energy content of food. You will burn a portion of food and capture the heat released by
placing the burning food beneath a beaker that contains a known mass of water. When you burn
the food, you can use the heat released as a determination of the energy content of that food.
To calculate the amount of heat energy released and transferred to the water, the initial and final
water temperatures must be taken then calculated:
In a study by Urban et al.
(2011), researchers used a bomb
calorimeter to measure energy content of
restaurant food items in order to compare
them to the stated estimated energy content.
Of the 269 food items studied, 50 of them
had energy contents of at least 100 Calories
more per portion than the Calories estimated
per portion of food. In some food items,
discrepancies were as high as 392 Calories
per portion more than the Calories
estimated by the restaurants.
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Experiment Caloric Content of Food
Equation 1. Determining the energy released by a reaction:
Where Q = heat energy absorbed (in Calories (kcal), ∆T, which is equal to T
final
–T
initial
is the change
in temperature (in °C), m = mass of substance that is heated (in grams), and C = specific heat
capacity (use water only and assume that the glass beaker is negligible). The specific heat capacity
of water (C
w
) is 1.00 cal/g °C. You will determine the percent difference of your findings compared
to what the nutrition label indicates is the amount of Calories in the food. In addition, you will use
the Atwater factors to calculate the amount of Calories in the food based only on looking at the
amount of carbohydrates, lipids, and proteins (in grams).
For example, suppose you built the calorimeter and a 2 g cracker was burned down to 1.6 g which
raised the temperature of 50 g of water by 10°C. Refer to Equation 1 to calculate the Calories
(kcal) per gram of food:
Step 1
Calculate the amount of energy released by the reaction:
As 0.4 g of food was burned:
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Experiment Caloric Content of Food
Step 2
Determine the Percent Difference between calculated and published:
Use the information on the food label to determine the theoretical value. Take the number of
Calories per serving and divide by the number of grams per serving to determine the theoretical
value for Calories per gram for the food. The experimental value is what you measured using the
calorimeter.
Because the package says that 15 g is 70 kcal, you would determine how many Calories are in 1
gram of food, and use as the “Theoretical Value.”
Then:
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Experiment Caloric Content of Food
Step 3
Determine Calories According to Atwater Factors:
According to the values on the box of crackers, 15 g of crackers has 10 g of total carbohydrates
(less than 1 g of fiber, so we are not going to subtract any fiber; if fiber is above 1 g, subtract
from the total g of carbohydrate), 3 g of total lipids (fat), and 1 g of protein. Therefore:
● Calories from Carbohydrates:
● Calories from Lipids (Fats):
● Calories from Proteins:
● Total Calories:
References:
1. Urban, Lorien E., Megan A. McCrory, Gerard E. Dallal, Sai Krupa Das, Edward Saltzman, Judith
L. Weber, and Susan B. Roberts. “Accuracy of Stated Energy Contents of Restaurant Foods.”
Journal of the American Medical Association 303, no. 3 (2011): 287-293. doi: 10.1001/
jama.2011.993
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Experiment Caloric Content of Food
Exercise 1: Determination of Caloric Content of
Three Foods
In this exercise, you will build a calorimeter to measure the caloric content of three foods: a nut,
a marshmallow (jumbo), and another sample of the food of your choice. You will compare your
data to the nutrition labels found on the packaging of these foods. In addition, you will calculate
the caloric estimation of the food as listed on the nutrition label and based on Atwater factors.
Procedure
1. Gather the materials listed for this experiment. It is necessary to perform this experiment on
a steady surface such as a tabletop, and in an area that is not carpeted as you will be burning
substances. You will also have to wash some materials with soap and water, so perform this
experiment near a source of tap water.
2. Place the 100-mL glass beaker on the digital scale and tare it.
3. Pour and weigh approximately 50 g of room-temperature distilled water into the glass beaker.
4. Record this value in Data Table 1 of your Lab Report Assistant.
5. Place the burner stand on the pie pan and then place the glass beaker with approximately 50
g of distilled water in it on the burner stand.
6. Put the thermometer in the beaker.
7. Use approximately 2 feet of aluminum foil to wrap around the burner stand and beaker to
minimize heat loss. The top of the aluminum foil should enclose the thermometer, but the
thermometer should be sticking out of the top of the aluminum foil for easy measurement.
One side of the foil should be open to allow for some air flow in order to keep the substance
burning underneath the beaker. See Figure 5.
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Experiment Caloric Content of Food
Figure 5. Complete setup of calorimeter.
8. Tare the scale and weigh the nut, the aluminum cup, and the test tube clamp all together.
Record the total mass (in grams) of these items in Data Table 2 in your Lab Report Assistant .
Write the type of nut that was used on the line provided in the column header next to “Type.”
9. Using the thermometer, stir the water and measure the temperature of the water in degrees
Celsius. Record the temperature in Data Table 2.
10. Hold the nut with the test tube clamp.
11. Outside of the aluminum foil, use a match to light a candle or use a lighter to ignite a flame
and then place the nut directly in the flame to catch the nut on fire.
Note: Using only matches (without a candle) is not recommended, as it may take more time to start
the food on fire than it takes for the matches to burn.
12. When the nut is on fire, immediately place it in the aluminum foil “tent” while still holding it
with the clamp, directly under the beaker. See Figure 6. Leave a portion of the aluminum foil
open just enough to keep the nut burning, and let it burn as long as possible.
13. Record any observations of the flame (including the amount of time it burned and intensity
of flame) in Data Table 2.
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Experiment Caloric Content of Food
Figure 6. Hold the clamp with the burning food directly under the beaker of water, leaving a
small opening in the aluminum foil to keep the food burning as long as possible.
14. When the nut is finished burning, set the remainder of the burned nut in the aluminum cup.
Set the clamp on the aluminum cup.
15. Immediately stir the water with the thermometer, and observe the reading of the thermometer
while it is in the water (but while reading it, hold the thermometer so it is not touching the
glass of the beaker). Record the reading in Data Table 2 in the row entitled “Water temp –
final (°C).”
16. Tare the scale, lay the clamp on the aluminum cup, and weigh the nut, aluminum cup, and
clamp together. Record the total mass of these 3 items in the row entitled “Mass of food, cup,
and clamp – final.”
17. Determine the change in water temperature, by subtracting the final temperature of the water
from the initial temperature of the water. Record the change in temperature in Data Table 2.
18. Determine the amount of the nut that was burned by subtracting the initial mass of the nut,
cup, and clamp from the final mass of the nut, cup, and clamp. Record the mass of the burned
food in Data Table 2.
19. Wash the clamp and aluminum cup if any food is stuck to it with soap and water, and dry it
with a paper towel. Dispose of the water in the beaker, and wash the beaker, using caution as
the beaker may be hot.
20. Repeat steps 2-19 using a marshmallow instead of a nut. Record values in Data Table 1 and
Data Table 2.
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Experiment Caloric Content of Food
21. Repeat steps 2-19 using another food of choice instead of a nut or a marshmallow. Record
values in Data Table 2.
Energy released by the reactions:
22. Use your results in Data Table 1 and Data Table 2 and the information provided in the
Background section to calculate the amount of heat produced per gram (in Calories/gram)
for each food, and record this value in Data Table 2.
Percent Difference:
23. Determine the energy per gram (kcal/g) that is estimated on the package for each food
according to the food labels. Record these values in Data Table 2.
24. Using “Step 2”, as outlined in the Background, determine the percent difference for each
food. Record the percent difference in Data Table 2.
Determination of Calories according to Atwater Factors (kcal/g):
25. Use the Atwater factors to determine the estimated kcal/g of each food according to the
nutrition label on the package. Record these values in Data Table 2 in the row entitled
“Determination of Calories according to Atwater Factors (kcal/g).”
Questions:
A. Compare the calorimeter that you built to a bomb calorimeter. How are they similar and
different?
B. Based on your results, was this setup a good way to measure Calories as opposed to a bomb
calorimeter? What types of experimental error may have occurred with this experiment? How
might you design this setup differently if you had unlimited expenses for materials?
C. Based on how each food burned, which food would be the best to use for a fuel that has a
steady flame and might burn for a long time? What was the composition of this food (which
macromolecule was it mostly composed of)? How does this relate to the way that the human
body utilizes this type of macromolecule as fuel?
D. Although protein was part of the composition of the foods in this experiment, it was not the
main macromolecule component of the nut or the marshmallow. Why do you think this type
of food may have been left out, based on what you learned about the way the fuel is “burned”
in the body?
E. Using your data, which food had the least amount of Calories per gram? Based on what you
learned about the structure of each macromolecule, why is this true?
F. When you determined the amount of estimated Calories in the foods based on Atwater
factors using the amounts of each macromolecule in the food, did you get the same number
as what was listed as the amount of Calories per serving on the nutrition label? If not, why do
you think there might be some discrepancy?
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Experiment Caloric Content of Food