FRESHMAN CLINIC I
Chocolate Coated Cookie Processing
Objectives
In this experiment you will be exposed to food processing, Good Manufacturing Practices
for the food processing and pharmaceutical industries, and some basic statistics. Your
group will coat Oreo cookies with chocolate, then recalculate a nutritional label and
perform a simple statistical analysis as an introduction to quality control.
Introduction
The chocolate manufacturing process offers a unique sequence of chemical engineering
unit operations. These operations can be isolated to demonstrate different chemical
engineering fundamentals. The raw material, cocoa beans, undergoes many diverse
processing steps depending on the desired final products. An overview of the chocolate
manufacturing process is shown in Figure 1. Briefly, fermentation and drying of the
cocoa beans is followed by shelling, roasting, and grinding to obtain a chocolate liquor
which is 55% cocoa butter. A series of separation and mixing processes are used to obtain
the final product whether it will be cocoa butter, cocoa powder, or other consumer
products such as milk or dark chocolate.
Figure 1: Process flow diagram for milk chocolate, chocolate syrup, and cocoa powder
[1].
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The semi-sweet chocolate used in this week’s experiment is a blend of chocolate products
such as cocoa powder, chocolate liquor, and cocoa butter that have been separated from
the raw material (cocoa beans) then re-mixed in the desired proportions with other
ingredients such as sugar, lecithin (an emulsifier), milk solids, and flavorings. These
diverse components present many challenges for processing of chocolate in terms of
mixing, fluid flow, and temperature control.
One contributor to the unique characteristics of chocolate is cocoa butter, which can
comprise as much as 50% of a finished chocolate product. Cocoa butter is a complex fat
with interesting properties; it is a mixture of fatty acids and glycerides. As chocolate
cools, crystals begin to form—chocolate has up to six crystalline structures, each with a
different melting temperature, from 17oC to 35oC. Chocolate must be melted, then
cooled, then melted again to achieve satisfactory crystal nucleation and uniform
crystallization responsible for the glossy sheen of good quality chocolate. If chocolate is
cooled too rapidly or slowly, or not tempered properly, the chocolate may solidify into
unacceptable unstable or super stable forms. One example of a super stable form is
known as “fat bloom” because the crystalline structures resemble blooms. Care must be
taken during processing to keep chocolate at the appropriate conditions to prevent this
phenomenon.
Before beginning any food processing or food handling, personnel must be trained in
Good Manufacturing Practices (GMPs). GMPs are important in the food and
pharmaceutical industries because the quality and safety of products from these industries
in particular can have a profound effect on the health of people who consume them.
Therefore, care must be taken to ensure that food and pharmaceutical products are free
from contaminants that might harm consumers. You will be introduced to some basic
GMPs during this experiment.
Chocolate manufacturing requires not only the skills specific to chemical engineering, but
all types of engineering expertise. When developing a new product or improving an
existing one, engineers can contribute in the following areas:
Chemical Engineering:
Making sure products that are developed in test kitchens have the same characteristics
when produced on a large scale. As an example of how chemical engineers play a role in
chocolate processing, the chocolate liquor or chocolate components and other ingredients
must be transported from storage or mixing tanks to other locations, such as enrobing
stations. Flow through pipes must meet all GMP requirements and also not change the
characteristics of the chocolate. Therefore, variables such as temperature, flowrate, and
pressure must be controlled. Chemical engineers also design packaging that retards food
spoilage, and may help with safety, GMP compliance, and wastewater treatment and
transport. Chemical engineers are often plant managers at food manufacturing facilities.
Mechanical Engineering:
Mechanical engineers help design and fabricate the large-scale equipment used in food
manufacture, and are also responsible for implementing systems for transporting finished
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products. Other areas in which mechanical engineers may contribute include packaging
design and bulk packaging.
Civil Engineering:
Civil engineers are concerned with how the plant interacts with the environment. They
design the building, and also work to make sure all discharges from the plant
(wastewater, air, etc.) are in compliance with government and local regulations. Civil
engineers may design on-site wastewater treatment facilities, or arrange for transport to
municipal treatment facilities.
Electrical Engineering:
Electrical engineers design systems that ensure each package contains the right amount of
candy bars or cookies. These engineers also design control systems for complex
processing steps.
Experiment
Your group will be provided with the following materials and equipment:
 Microwave oven (shared)
 Glass bowls
 Kitchen utensils
 Trays and wax paper
 Refrigerator (shared)
 Balance
 Stopwatch
 Temperature probe
 Cookies (9)
 Chocolate (5 squares)
 Plastic Rubbermaid container
Procedure:
1. Wash hands thoroughly.
2. Don hair net (and beard net if you have facial hair)
3. Assign the following tasks to group members: record keeping, measurements
(cookie weight), cookie coating, time keeping.
4. Obtain all necessary equipment and materials.
5. Open a package and place 9 cookies in plastic container.
6. Weigh all cookies, keeping cookies in sequence.
7. Melt 5 squares of Baker’s semi-sweet chocolate or 140 g of chocolate chips for 2
periods of 1 min, stirring after the first minute. Chocolate may not be completely
melted—stir until small chunks disappear.
8. Coat cookies in the same order as they were weighed. Coating should be
performed by the same person for consistency. The cookie coater should dip each
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cookie for the same amount of time, and allow cookie to drip until excess
chocolate stops flowing from cookie. “Dip” and “drip” time should be the same
for each cookie. Excess chocolate should be removed from the bottom of the
cookie by scraping a knife along the bottom of the fork holding the cookie.
9. After each cookie is coated, place on a cookie sheet covered with wax paper.
Once all cookies are coated, place cookies in refrigerator to cool for ~20 minutes.
10. Remove cookies from refrigerator, and weigh each coated cookie.
Data analysis
1. Use the AVERAGE and STDEV function in Excel to calculate an average uncoated
and coated cookie mass in Table 1:
Table 1: Data and calculations for coated and uncoated cookies
Cookie #
Mass uncoated cookie (g) Mass coated cookie (g)
1
2
3
4
5
6
7
8
9
Average cookie mass
Standard deviation
Share your individual cookie weights with another group. Recalculate the standard
deviation. How does your standard deviation change?
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2. Using your average value
for the coated cookie and
the information in Figures 2
and 3, recalculate a
nutritional label for a
serving size of 2 cookies.
Your label should include
grams and percent daily
values of total fat, saturated
fat, cholesterol, sodium,
total carbohydrates, dietary
fiber, sugars, and proteins,
as well as percent daily
values of vitamin A,
vitamin C, iron, and
calcium.
Hint:
first
check
calculation of total calories
based on the knowledge
that each gram of fat
contains 9 calories, each
gram of protein contains 4
calories, and each gram of
carbohydrate contains 4
calories.
Figure 2: Nutritional label for oreo cookies
Figure 2: Nutritional label for oreo cookies
You
may
find
some
discrepancies between total
reported calories and calculated
calories.
Where might the
error lie?
Your nutritional label should
follow a format similar to the
one shown in Figures 2 and 3,
reporting percent daily values,
and serving size (2 cookies).
Figure 3: Nutritional label for semisweet chocolate
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Report
Your report must contain the following elements:
1. An introduction explaining the objectives of the experiment and some background on
chocolate.
2. A brief materials and methods, including some commentary on GMPs
3. A results and data analysis section in which a recalculated nutritional label and
statistical analysis is presented. A brief explanation of your method for recalculating
your nutritional label, as well as some commentary on possible reasons for any trends
observed should be included in this section. Do not present a table of all cookie
weights. Instead, compare your group’s results (average weight and standard
deviation) with your combined results (yours and another group’s weights and
standard deviations). Does your standard deviation change? Why or why not?
4. In your results and data analysis section, also compare your average coated weight
and nutritional information for 2 cookies to the nutritional information for
commercially available “fudge covered oreo” cookies. Note that the serving size is 1
cookie—multiply their values by 2 to compare with your cookies.
5. A conclusions and recommendations section that includes some discussion on how to
make your chocolate coating process more consistent.
6. An appendix with raw data and sample calculations.
In your report, remember to:
 Label figures
 Use headings for different sections
 Number pages
 Cite any references used
Reference
[1]
B. L. Zoumas and J. F. Smullen, "Chocolate and Cocoa," in Encyclopedia of
Chemical Technology, vol. 6, K. Othmer, Ed., 3rd ed. NY: John Wiley & Sons,
1979, pp. 177-199.
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