4.2: Lab - The Caloric Content of Food
- Page ID
- 438408
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Beta-Testing Notes
Location of supplies: H3233 (1151K Lab) – Next to the CRC References
- Please use rubber bands to close the food bag. Additionally, there are Ziploc bags (1-gallon and 2-gallons) provided with sealing the opened food items.
- Please do not dispose of the soda cans.
Equipment and Materials
Prepare 12 sets of equipment and materials for 24 students per class section. Include a few more for backup if needed. Each set should include
Equipment
- Glass rod
- Ring
- Ring stand
- Thermometer or Vernier temperature probe
- Cork stopper
- Hot pad
- Distilled water
Materials
- Empty Soda Can
- Large Paper Clips
- Food Samples: Cheetos\(\circledR\), Reduced Fat Puffs, Protein Puffs
- Student or Beta-Tester provided: A solid snack food item of your choice
- Lighter or Matches
- Understand how caloric content is measured
- Determine the energy content of various foods
Laboratory Skill
- The use of a homemade calorimeter
Equipment and Materials
- Empty Soda Can
- Glass rod
- Ring
- Ring stand
- Funnel
- 3-prong extension with clamp
- 50-mL Graduated cylinder
- Thermometer or Vernier temperature probe
- Large paper clips
- Cork stopper
- Food Samples: Cheetos\(\circledR\), Reduced Fat Cheetos\(\circledR\), Protein Puffs\(\circledR\), A solid snack food item of your choice
- Hot pad
- Distilled water
- Lighter or Matches
Safety and Hazard Information
- Before the beginning of the lab ensure that you can locate the lab’s fire extinguisher and pull back your hair if it is long. Clear your benchtop of any unnecessary debris (especially paper). Exercise caution at all times while using the lighter and igniting the food items. If, at any time, something other than the food or matches ignite, immediately inform the instructor. If any clothes or accessories on your body catch fire, stop, drop and roll.
Background Information
The expected caloric content in food is associated with carbohydrates, fat and protein. The Food and Drug Administration (FDA) has regulated the reporting of such macronutrients (carbohydrates, fats, protein) on food items in the United States. The label is referred to as the Nutrition Facts label on food packaging. This label provides the size of the serving (in grams or ounces [1 ounce (oz) ~ 28.3 grams]). Appropriate scaling of the food serving size has to be taken into consideration for accurate caloric content. Typical energy content values (kcal/g) for the macronutrients are:
| Carbohydrate – 4 kcal/g | Fat – 9 kcal/g | Protein – 4 kcal/g |
In order to obtain caloric content in food, food scientists perform an indirect measure of the amount of heat generated from the burning or combusting of a food item. Surprisingly, the combustion of food is very similar to what takes place in your body. After digestion, food is generally converted into glucose and combined with oxygen in a combustion reaction to generate energy for your body. When measuring the energy content of food in the lab, water is the medium that is used to monitor this heat that is generated. A calorimeter is usually an isolated environment in which the heat absorbed or generated can be accurately measured. The temperature change of the water, combined with its mass and heat capacity, allow for the heat released by a food item to be determined.
The equation for heat capacity (\(q\)) is:
\[q = m \cdot C \cdot \Delta T \label{1}\]
where \(m\) = mass of system in grams, \(C\) = specific heat capacity of the medium (water, for this lab) in \(\frac{\text{cal}}{g \cdot ^{\circ}\text{C}}\), and \(\Delta T\) = temperature change in \(^{\circ}\)C.
The specific heat capacity of water is 1 calorie per gram per \(^{\circ}\)C \(\left( 1\frac{\text{cal}}{g \times ^{\circ}\text{C}}\right)\). The calorie in this compound unit is a scientific calorie. A conversion is required between scientific calories (calories) to food calories (Calories): 1 Cal (food) = 1000 cal (scientific) = 1 kcal (scientific).
You will construct a calorimeter using a soda can. The food will serve as the system and the suspended water will be the surroundings. As a result of the conservation of energy, the sum of the heat of the system (\(q_{sys}\)) and the heat of the surroundings (\(q_{surr}\)) must equal zero calories:
\[q_{sys} + q_{surr} = 0 \label{2}\]
So, you will really monitor the \(q_{surr}\) which represents:
\[q_{surr} = -q_{sys} \label{3}\]
This negative quantity for heat of the system is heat released by the system.
The change in temperature of a system can provide a representation of the amount of heat that the system (food) absorbs. In this experiment, you will expose a soda can of distilled water to the heat generated by the combustion of a solid food item. The food items in this lab include regular Cheetos\(\circledR\), Reduced Fat Cheetos\(\circledR\), a protein puff (brand will be available in lab) and a solid food item of your choice. The food item will be suspended below the can of water. Once ignited, the observation of initial and final temperatures of the water in the can will provide data on the temperature difference in degrees Celsius.
Procedure
Measuring the caloric content of food
1. Measure the mass (in grams) of the can. Record it on the Experimental Report.
2. Construct the soda can calorimeter according to Figure \(\PageIndex{1}\).
Insert the glass rod through the loop of the can opening. Suspend the glass rod above the ring. Clamp the three-prong extension on the ring stand (above the ring) and place the temperature probe (or thermometer) in the three-prong extension and ensure that the probe just above the bottom of the can. Make sure that the cord for the temperature probe is away from any open flames.
3. Use a 50-mL graduated cylinder to fill the soda can with 50 mL of distilled water. Use a funnel as needed for the liquid transfer. Measure the mass (in grams) of the water and record it on the Experimental Report.
4. Anchor the Cheeto\(\circledR\) below the soda can using the large paper clip on a cork as shown in Figure \(\PageIndex{2}\). Adjust the height of the food item within 1-2 inches of the bottom of the can.
5. Weigh a regular Cheeto\(\circledR\) on the cork/paper clip stand and record the mass (in grams) in Table \(\PageIndex{1}\). Be sure to include all digits viewable on the balance; all digits are significant!
6. Record the initial temperature (in Celsius) of the water in Table \(\PageIndex{1}\).
7. Carefully ignite the Cheeto\(\circledR\) using a lighter or matches.
8. Once the Cheeto\(\circledR\) is fully combusted, record the final temperature (in Celsius) of the water in Table \(\PageIndex{1}\). Then remove the ignited food item using the cork stand and blow out the flame.
9. Once the food item has cooled, carefully take that burned food item on the cork stand to the balance to weigh the burned product. Record this mass in Table \(\PageIndex{1}\).
10. Allow the water to cool to within a few degrees of the initial temperature. If needed, use the hot pad to move the soda can and just replace the heated water with a new sample of water.
11. Repeat steps 3 to 8 with each other food item.
Experimental Report
Mass of the can: _______________________________________ grams
Mass of water in can: _________________________________ grams
Table \(\PageIndex{1}\): Water temperature before and after food combustion
| Food | Mass of Food Sample + Stand (\(g\)) | \(T_i (^{\circ}\)C) | \(T_f (^{\circ}\)C) | \(\Delta T (^{\circ}\)C) | Mass of Burned Sample + Stand (\(g\)) | Mass of Food Consumed (\(g\)) |
|---|---|---|---|---|---|---|
| Cheetos\(\circledR\) | ||||||
| Reduced Fat Cheetos\(\circledR\) | ||||||
| Protein Puffs | ||||||
|
A Solid Food of Your Choice: ________________ |
Data Analysis
Calculate the mass of the water or mass of the surroundings:
\[\text{Mass of water } = (\text{Mass of can }+ \text{ water}) - (\text{Mass of can}) \label{4}\]
Temperature change:
\[ \Delta T (^{\circ}\text{C}) = T_f (^{\circ}\text{C}) - T_i (^{\circ}\text{C}) \label{5}\]
Calculate the change in temperature (as shown in Equation \ref{5} above) of the water of each combusted food item and report this difference in Table \(\PageIndex{1}\).
\[\text{Mass of food consumed } = \text{ Mass of food sample with stand } - \text{ Mass of burned sample with stand} \label{6}\]
Calculate the change in mass (as shown in Equation \ref{6} above) of the food item and report this difference in Table \(\PageIndex{1}\).
Using the temperature change, mass of the surroundings, and the specific heat capacity of water (1 cal per \(g\) per \(^{\circ}\)C) and Equation \ref{1}, determine the quantity of heat (\(q\)) released by combusting each food per gram food consumed in Table \(\PageIndex{1}\). Record this energy/mass value (in calories/gram) in Table \(\PageIndex{2}\), Column 1.
Table \(\PageIndex{2}\): Caloric content of various foods
| Food | Heat released (in calories/gram food) | Heat released (in Food Calories/gram food) | Expected Food Calories (Cal/gram) from Macronutrients | Percent Error (%) |
|---|---|---|---|---|
| Cheetos\(\circledR\) | ||||
| Reduced Fat Cheetos\(\circledR\) | ||||
| Protein Puffs | ||||
| A Food of Your Choice |
Convert the scientific calories above in Column 1 of Table \(\PageIndex{2}\) into food calories and report this value in Column 2 of Table \(\bf\PageIndex{2}\). 1 Cal (food) = 1000 cal (scientific) = 1 kcal (scientific).
Follow-up Questions
Using information on the nutrition label of the food sample, calculate the Cal/gram. (Divide Calories per serving by the number of grams in a serving.) Report this quantity (in Food Calories) in Column 3 of Table \(\bf\PageIndex{2}\).
\[\text{Percent Error } (\%) = \frac{|\text{Experimental Value }-\text{ Accepted Value}|}{\text{Accepted Value}} \times 100 \label{7}\]
Calculate the percent error (use Equation \ref{7} above) between the expected calories as calculated by the macronutrient content with your experimental determination of the caloric content. Report this percentage in Column 4 of Table \(\bf\PageIndex{2}\).
In your calculation, you assumed that all the heat released by the combusted food item was absorbed by the water. Do you think this is true or not? If it is not true, would this tend to make your estimated calories too big or too small?
Use the macronutrients (product reported quantities of carbohydrates, fat, and protein) of each food item to determine the energy content (kcal) per gram of the combusted foods and report this below. (Multiply the bolded energy content by the mass of the respective macronutrient.) Which food had the highest energy content per gram? Why?
| Carbohydrate – 4 kcal/g | Fat – 9 kcal/g | Protein – 4 kcal/g |