How is the energy value of foods determined

Caloric Content of Food

Chelsey Grasham

Lab Report Assistant

Purpose: The purpose of this experiment was to compare the calorie content of certain foods after finding the energy capacity of those foods. Also, a purpose of this experiment was to learn what calories really are.

Procedure: In this experiment, I weighed foods, made my own calorimeter to find the actual weight of the food, after I calculated the temp. of the water. I did this for the chip, pistachio, and marshmallow.

Conclusion: In conclusion, this experiment taught me how to effectively measure calories, compare calories between foods, and overall see how calories and certain foods affect the human body.

Exercise 1: Determination of Caloric Content of Three Foods

Data Table 1. Mass (g) of the Water.

Nut

Marshmallow

Chip

Mass of the water

45.8

44.7

49.2

Data Table 2. Caloric Calculations.

Food Item Description:

Nut (Type: green pistachio)

Marshmallow (Jumbo)

Other Sample (Chip)

Mass of food, cup, and clamp – initial

29.1 g

34.1 g

29.6 g

Mass of food, cup, and clamp – final

28.9 g

33.6 g

29.3 g

Mass of burned food

0.2 g

0.5 g

0.25 g

Observations of the Flame (intensity, length of time burning, etc.)

The pistachio caught on fire really quickly and it burned for a couple minutes

The marshmallow caught on fire and turned black but it only burned for maybe 8 seconds

The chip caught on fire quickly and burned for about 60 seconds with a small flame

Water temp – initial (°C)

31.0

28.1

31.1

Water temp – final (°C)

35.6

32.2

35.2

Change in temp (ΔT) (°C)

4.6

4.1

4.0

(Q) Energy Released (kcal/g)

1.2 kcal/g

0.35 kcal/g

0.8 kcal/g

Energy Estimated on Package (kcal/g)

5.7 kcal/g

1.7 kcal/g

5.4 kcal/g

Percent Difference

81%

80%

85%

Determination of Calories according to Atwater Factors (kcal/g)

6.1 kcal/g

3.3 kcal/g

5.5 kcal/g

Questions:

A. Compare the calorimeter that you built to a bomb calorimeter. How are they similar and different?

Similar: constant volume and temperature

Different: caught fire outside of water, not enclosed, no stirring of water

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? I thought this way a fairly simple at home way to measure calories as opposed to bomb colorimeters which are harder to make than the one I made. An error that I think occurred was that the heat started to come out of the tent so the heat started to become lost. If I had unlimited expenses I would probably try to recreate a real calorimeter instead of a make shift one.

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? Based on how each food burned, the chip and the pistachio burned the longest because of their carb and fat content. This is logical because the human body burns carbs and fats the slowest.

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? I think this is because protein in the body is not used for energy immediately, it is stored and used later.

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? The marshmallow had the least amount of calories per gram. This is true because there’s no fat.

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? The numbers were not the same. There might be some discrepancy because usually companies will round up when they are making calorie labels.