Full points received IB Biology SL Internal Assessment (IA) from May 2019 alumni. The experiment was conducted on the effects of increasing Theobroma cacao (cocoa that we know) content on energy in kilocalories (kcal).
Research Question: Does higher Theobroma cacao content in chocolate give out more
energy in kilocalories?
Background Information
Calorimetry is the science of measuring the change of energy involved in a chemical
process. Although there are many different designs of calorimeters, each is devised to
measure the heat that is released or absorbed during a chemical reaction. (Calorimeter)
The heat transferred is named as the calorie and the ‘calorie’ used in nutrition, usually
called the Calorie with a capital ‘C’ is a kilocalorie. A calorie is required to raise the
temperature of 1 gram (g) of water 1 degree Celsius (°C). (Gunnars)
All foods contain energy, but the potential energy stored in a particular food depends on its
composition of macronutrients, which takes us to the main focus of this experiment,
Theobroma cacao (Acevedo-Rodríguez et al.) or the cacao tree where a delicious piece of
chocolate all starts. The whole tree, its pods and beans are referred to as “cacao” while
“cocoa” is known as the dried and fully fermented cacao seeds. This is the basis for the
ground of obtaining cocoa liquor which is pressed to eventually yield cocoa powder or
cocoa butter. It is often said that the darker the chocolate is, the healthier it gets which has
a direct linkage to how much, by weight, is from pure cocoa beans (Rancourt). Before this
is taken into consideration, it should be noted that regardless of the percent cacao,
chocolate is comparatively high in calories, both in terms of sugar and fat. However, the
difference an increased cocoa mass makes comes from the difference in its nutrients; as
cacao percentage increases, total fat and saturated fat increases, while carbohydrates and
sugar decrease (Rancourt). Therefore, increased fat that comes from cocoa butter leads to
more calories. Nonetheless, various studies indicate more than half of the saturated fat
found in the cocoa bean comes from stearic acid, which is a fatty acid that helps improve
cholesterol levels. Furthermore, the cocoa bean is one of the most concentrated sources
of flavanols, which is a subgroup of the natural antioxidant plant compounds called
flavonoids. (Erdman 2008) Taking all of these into consideration, dark chocolate seems as
if it is a great source of energy while at the same time being a more beneficial choice of
chocolate.
I specifically chose this research question because I have been significantly involved in
fitness since I have lost more than 23 kgs which led me to maintain a balanced and
healthy diet and have a better understanding of nutrients. Therefore, one or two pieces of
dark chocolate have always been a great source of energy for me before working out
compared to milk chocolate, while at the same time being a healthier option. I often go for
the highest percentage of cacao I can found in chocolate and there are various
percentages put up by food manufacturers. This made me curious to see if the increasing
cacao mass content in chocolate indeed leads to a higher temperature—or in other words
higher energy content which I will find in terms of kilocalories.
Hypothesis
Null Hypothesis (H0): The three chocolates will increase the energy content in kcal,
however there will be no substantial difference in the findings.
Alternate Hypothesis (H1): As the cacao percentage increases, the energy content in
kcal will significantly increase likewise.
!1
, Variables
Independent Variables: Types of chocolate — Depending on the brand, the nutritional
content of each chocolate type will vary in cacao mass.
The 3 types of chocolate were of brands:
• Brand A — minimum of 25% cocoa solids
• Brand B — minimum of 54% cocoa solids
• Brand C — minimum of 99% cocoa solids
Dependent Variable: Energy content, measured in the increase of temperature of a fixed
volume of water. (°C) (±0.5)
Controlled Variables:
• The volume of water for each trial was kept at 50ml for accurate calculations and fair
comparison.
• The room temperature was kept at 24°C by closing the windows when exceeded, and
opening when normalised to remove external factors that could interfere with the heating
or cooling of the water.
• The distance between the burning chocolate piece and the test tube was kept the same
to reduce inaccuracy and irrelevant variation in the findings.
• The initial mass of chocolate piece and the filter paper that protected the sample from
dropping or melting over the tongs were kept the same to reduce inaccuracy.
• The set-up used for all trials throughout the experiment was kept the same to reduce
inaccuracy in findings.
• Each chocolate piece was burned until it could not burn anymore.
Materials
• Tap water, 50ml (± 2.00) — for each trial (750g in total)
• Vernier Stainless Steel Temperature Probe TMP-BTA — to measure the change in
temperature (°C) (± 0.5°C)
• 50ml Measuring Cylinder (± 2.00ml)
• Vernier LabQuest — for data collection
• Glass Dishes — to cut the chocolate pieces in, keeping the laboratory clean
• A lighter — to ignite the samples
• A mass balance (± 0.01g) — used to measure the mass of samples wrapped in filter
papers
• A clamp stand — to hold the water cylinder in place
• A homemade calorimeter — constructed from two insulators to keep flame just below the
test tube that is clamped firmly by the clamp stand.
• Tongs — to hold the sample during combustion
!2
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