Food of the gods… Model 1. Chocolate is a product of the cacao bean – a seed found within the fruit of the cacao tree, Theobroma (“food of the gods”) cacao. When removed from the fruit, the cacao bean is astringent, bitter and practically aroma-less. Since it is a seed, it contains the embryo of the cacao tree, as well as protein and fat (cacao butter) to nourish the seedling, and defensive compounds that deter animals from eating the seeds. The defensive compounds include astringent phenolics, anthocyanins, and two bitter alkaloids – theobromine and caffeine. Figure 30.1 (L) Roasted cacao bean cut in half (R) Raw cacao bean cut in half (image licensed under creative commons) The cacao seed is also ~65% water. Cacao fruit is a pod filled with many cacao beans/seeds embedded in a sugary pulp. When the fruit is mature, the pulp and seeds are removed and fermented. During fermentation the sugary pulp is consumed by yeast and bacteria. The yeast convert sugar (C6H12O6) to ethanol (C2H6O), and the bacteria use oxygen to convert the ethanol (C2H6O) into acetic acid (C2H4O2, the acid in vinegar). glucose ( C 6 H 12 O 6 ) C C C C C O H OH H H OH H OH CH 2 H HO OH yeast H 3 C CH 2 OH + 2 CO 2 2 O 2 H 3 C C OH O acetic acid ethanol O 2 2 bacteria destroys cell membranes of cacao beans Over time, the acetic acid breaks down cell membranes of the cacao seed, and the defensive compounds mix with enzymes and air. Figure 30.2. Fermentation of the cacao fruit pulp converts glucose sugars into acetic acid. As we have seen with browning of fruits and vegetables (Activity 21_Plants and Color), when phenolics mix with enzymes and air, oxidation turns the astringent phenolics into brown colored compounds that are less astringent. When the membranes are weakened by acid, released enzymes also break down the proteins inside the seed/bean into amino acids. After the fermentation, the beans are dried in preparation for roasting. Table 30.1. The Composition of Fermented Dried Cacao Beans Molecule % by weight Molecule % by weight Water 5 Sugars 1 Proteins and amino acids 12 Phenolic compounds 6 Cacao butter (fat) 54 Minerals 3 Starch 6 Theobromine (an alkaloid) 1.2 Fiber 11 Caffeine (an alkaloid) 0.2 Roasting uses dry heat to remove much (but not all) of the vinegary acetic acid by evaporation, and generate the browning Maillard reactions between the amino acids and sugars. Finally the heat develops flavor molecules from the Maillard reactions and the breakdown of some defensive compounds. This is similar to the process used to roast coffee beans. Chemists have detected over 600 different kinds of volatile molecules in chocolate – making it one of the most aromatic foods in the world. Figure 30.3. Cacao nibs (image licensed under creative commons) The inside of the cacao bean (the bean minus the shell) is called a kernel or nib. Since the shell is made of mostly fiber, the nibs were the “guts” of the cacao seed, and contain all of the cacao but ...

1. Food of the gods…
Model 1. Chocolate is a product of the cacao bean – a seed
found within the fruit of the cacao tree, Theobroma (“food of
the gods”) cacao. When removed from the fruit, the cacao bean
is astringent, bitter and practically aroma-less. Since it is a
seed, it contains the embryo of the cacao tree, as well as protein
and fat (cacao butter) to nourish the seedling, and defensive
compounds that deter animals from eating the seeds. The
defensive compounds include astringent phenolics,
anthocyanins, and two bitter alkaloids – theobromine and
caffeine.
Figure 30.1 (L) Roasted cacao bean cut in half (R) Raw cacao
bean cut in half (image licensed under creative commons)
The cacao seed is also ~65% water. Cacao fruit is a pod filled
with many cacao beans/seeds embedded in a sugary pulp. When
the fruit is mature, the pulp and seeds are removed and
fermented. During fermentation the sugary pulp is consumed by
yeast and bacteria. The yeast convert sugar (C6H12O6) to
ethanol (C2H6O), and the bacteria use oxygen to convert the
ethanol (C2H6O) into acetic acid (C2H4O2, the acid in
vinegar).
glucose
(
C
6
H
12
O

2. 6
)
C
C
C
C
C
O
H
OH
H
H
OH
H
OH
CH
2
H
HO
OH
yeast
H
3
C
CH
2
OH
+
2
CO
2
2
O
2
H
3

3. C
C
OH
O
acetic
acid
ethanol
O
2
2
bacteria
destroys
cell
membranes
of
cacao
beans
Over time, the acetic acid breaks down cell membranes of the
cacao seed, and the defensive compounds mix with enzymes and
air.
Figure 30.2. Fermentation of the cacao fruit pulp converts
glucose sugars into acetic acid.
As we have seen with browning of fruits and vegetables
(Activity 21_Plants and Color), when phenolics mix with
enzymes and air, oxidation turns the astringent phenolics into
brown colored compounds that are less astringent. When the
membranes are weakened by acid, released enzymes also break
down the proteins inside the seed/bean into amino acids. After
the fermentation, the beans are dried in preparation for roasting.
Table 30.1. The Composition of Fermented Dried Cacao Beans
Molecule
% by weight
Molecule
% by weight

4. Water
5
Sugars
1
Proteins and amino acids
12
Phenolic compounds
6
Cacao butter (fat)
54
Minerals
3
Starch
6
Theobromine (an alkaloid)
1.2
Fiber
11
Caffeine (an alkaloid)
0.2
Roasting uses dry heat to remove much (but not all) of the
vinegary acetic acid by evaporation, and generate the browning
Maillard reactions
between the amino acids and sugars. Finally the heat develops
flavor molecules from the Maillard reactions and the breakdown
of some defensive compounds. This is similar to the process
used to roast coffee beans. Chemists have detected over 600
different kinds of volatile molecules in chocolate – making it
one of the most aromatic foods in the world.
Figure 30.3. Cacao nibs (image licensed under creative
commons)
The inside of the cacao bean (the bean minus the shell) is called
a kernel or nib. Since the shell is made of mostly fiber, the nibs
were the “guts” of the cacao seed, and contain all of the cacao
butter (fat) and other cacao molecules; nibs are essentially raw

5. chocolate. Manufacturers then grind the nibs into very, very
small particles (0.02-0.03mm).
The particles are so small that the resulting material - called
chocolate liquor - is essentially the molecules (protein, fiber,
starch, sugar phenolics, alkaloids) suspended in the fat.
Chocolate liquor has a concentrated chocolate taste, but is still
quite bitter, astringent and acidic. The chocolate liquor is
further modified to make the chocolate we are used to eating. If
most of the fat is extracted from the chocolate liquor, the
resulting powdery solid is made into unsweetened cocoa powder
– often used in baking. The isolated fat or cocoa butter can be
added back to the chocolate liquor to increase the total amount
of fat and change the consistency of the final chocolate.
Table 30.2. The Composition (given in % of chocolate weight)
of different types of eating chocolate
% (percentage) by weight
Chocolate liquor
Added
cocoa butter
Added sugar
Added
milk solids
Total fat
Total carbohydrate
Total protein
Baking chocolate
Unsweetened
(solid baking chocolate)
99
0
0

6. 0
53
30
13
Dark Chocolate
(Bittersweet > semisweet)
70-35
0-15
30-50
0
25-38
45-65
4-6
Eating chocolate
Dark Chocolate (sweet)
15
20
60
0
32
70
2
Milk chocolate
10
20
50
15
30
60

7. 8
“white” chocolate
0
20
55
30
32
59
6
Unsweetened cocoa powder
(also for baking, cocoa butter is removed from chocolate liquor)
20
40
15
Vanilla (bean, extract or artificial) and lecithin are also
common additives to eating chocolate. Remember lecithin is a
soy derived phospholipid emulsifier, and emulsifiers are
amphiphilic molecules that help mix polar (hydrophilic) and
non-polar (hydrophobic) molecules. Lecithin is especially
useful in dark and milk chocolate where there is a large amount
of added sugar. The lecithin helps the fat mix with the sugar
. Typically lecithin is no more than 0.3-0.5% of the chocolate
weight.
“Dutch” or alkalized cocoa powder is produced from cacao
beans that have been treated with the alkaline substance,
potassium carbonate. This raises the pH of the cacao beans to a
neutral pH 7 or a slightly alkaline pH 8. The change in pH also
has effects on the chemistry of the chocolate, the most notable
of which is the reaction of flavor molecules with phenolics to
produce flavorless dark colored compounds. Thus, alkalized
cocoa powder is milder in flavor and has a darker color. Since

8. natural cocoa powder is acidic and “Dutch” or alkalized cocoa
powder is neutral or basic, using the right one for a recipe is
important.
Questions:
1. A raw cacao bean has a purple colored interior. Which of the
defensive compounds within the cacao bean could be
responsible for the purplish color of its interior?
2. Why is chocolate liquor…
a. …essentially molecules suspended in fat?
b. …acidic?
3. What molecule(s) are primarily responsible for the bitter
taste of dark chocolate (the darkest chocolate is synonymous
with bittersweet)?
4. Why does unsweetened cocoa powder have less than half the
total fat content of unsweetened baking chocolate?
5. White chocolate seems like an oxymoron….
a. Does white chocolate contain caffeine? Why or why not?
b. White chocolate has no chocolate flavor. What is the
chemical explanation for this (i.e. what molecules are
responsible for chocolate flavor and why doesn’t white
chocolate have any?)
c. Some white “chocolate” is made with solid or hydrogenated
vegetable fats instead of cocoa butter. Is this stuff rightly called
white chocolate? Why or why not?
6. In the Joy of Cooking, the authors recommend the following
substitutions for natural or Dutch processed (alkalized) cocoa
powder – if you find yourself without the necessary cocoa

9. powder for the recipe:
· Substitution for 3 tablespoons (18 grams) Dutch-processed
cocoa: 3 tablespoons (18 grams) natural cocoa powder plus
pinch (⅛ teaspoon) baking soda
· Substitution for 3 tablespoons (18 grams) natural cocoa: 3
tablespoons (18 grams) Dutch-processed cocoa plus ⅛ teaspoon
cream of tartar or ⅛ teaspoon lemon juice or vinegar
What is the chemical reasoning behind these recommended
substitutions?
What makes chocolate so special?
Model 2. One of the reasons chocolate is special is the
temperature at which it melts. Chocolate melts between 94-97°F
thanks to the sharp melting point of cocoa butter (the fat that
comprises over half of the chocolate weight), which is right at
human body temperature (~98°F). Chocolate literally “melts in
your mouth”. Although cocoa butter is a plant fat, is it
comprised of over half saturated fats. These saturated fats make
cocoa butter a solid at room temperature
(hence the “butter” reference), and the relatively small number
of fatty acid types makes the cocoa butter solid melt over a
relatively narrow temperature range (remember, the melting
temperature of a solid is influenced by the purity/homogeneity
of the solid – Activity 11).
Table 30.3. % Fatty acids that comprise the triglycerides found
in the oil/fat
Fats
Saturated
Mono
unsaturated
Polyunsaturated
Oil/Fat
Capric Acid
Lauric Acid

10. Myristic Acid
Palmitic Acid
Stearic Acid
Oleic acid
Linoleic Acid
α-linolenic acid
Butterfat (cow)
3
3
11
27
12
29
2
1
Cocoa butter
--
--
--
25
38
32
3
--
Olive Oil
--
--
--
13
3
71
10
1
Diets high in saturated fats may raise the risk for heart disease,
which sounds like bad news for eating chocolate!
However….despite cocoa butter’s higher than typical

11. concentrations of saturated fats, the saturated fat in largest
concentration – stearic acid – is immediately converted by the
enzymes in the body to oleic acid, a cis monounsaturated fat.
So, chocolate’s effective saturated fat content is low er thanks to
the stearic to oleic acid conversion, and scientists do not
believe that chocolate consumption poses cardiovascular risks.
C
O
O
C
H
2
C
C
CH
2
C
H
2
H
2
C
C
H
2
H
2
C
C
H
2
H
H
C

12. H
2
H
2
C
C
H
2
H
2
C
C
H
2
H
2
C
C
H
2
H
2
C
C
H
2
H
2
C
C
H
2
H
2
C
C

13. H
2
H
2
C
C
H
2
H
2
C
CH
3
H
2
C
C
O
O
C
H
2
H
2
C
C
H
2
H
2
C
CH
2
H
2
C

14. H
3
C
Stearic
Acid
-
an
18
carbon,
saturated
fatty
acid
(found
in
high
concentrations
in
cocoa
butter)
part
of
tricglyceride
part
of
tricglyceride
enzymes
in
the
human
body
Oleic
Acid
-
an
18
carbon,

15. cis
monounsaturated
fatty
acid
Figure 30.4. The conversion of stearic acid (a saturated fatty
acid) to oleic acid (a cis monounsaturated fatty acid) by
enzymes in the human body.
Many people believe chocolate can alter their mood, and
chocolate does contain molecules that have effects on the brain.
These molecules are part of the cacao seed’s chemical defenses
against predators and are present in the bean when it is
harvested, fermented and roasted.
Table 30.4. Psychoactive molecules found naturally in the cacao
bean and therefore in chocolate
Molecule
Structure
Physical Effects
Caffeine
N
C
N
C
C
C
N
C
H
N
O
O
H
3
C

16. C
H
3
C
H
3
Stimulant of the central nervous system
1oz of unsweetened chocolate contains 30 milligrams of
caffeine (~⅓ that found in a cup of coffee)
Theobromine
H
N
C
N
C
C
C
N
C
H
N
O
O
C
H
3
C
H
3
Stimulant of the central nervous system (although weaker than

17. caffeine) and toxic to dogs
.
1oz of unsweetened chocolate contains ~300 milligrams of
theobromine
Anandamide
H
2
C
C
C
C
C
C
H
2
C
H
2
C
C
C
C
C
H
2
H
2
C
C
H
2
C

18. O
N
H
H
2
C
C
H
2
O
H
H
2
C
C
H
2
H
2
C
C
H
2
C
H
3
H
H
H
H
H
H
H
H
A molecule found in chocolate and also produced naturally by

19. the human brain that blocks pain and depression
If anandamide looks a little like a cis polyunsaturated fatty acid
to you…you would be right – that’s what anandamide is made
from.
Phenylethylamine (PEA)
H
C
H
C
C
H
C
H
C
H
C
H
2
C
C
H
2
N
H
2
A molecule found in chocolate and also produced naturally by
the human brain which stimulates the parts of the brain that
keep you alert and mimics the brain chemistry of a person in
love.
Scientists believe that other molecules in chocolate inhibit the
breakdown of PEA in the brain, allowing its effects to last

20. longer.
But can chocolate actually be good for your heath? As a seed,
the cacao bean contains alkaloids (caffeine, theobromine),
anthocyanins, phenolics and polyphenols (made from phenolics)
for chemical defense. Molecules like phenolics and polyphenols
are great antioxidants – they protect against oxidative damage
from the oxygen we breathe by reacting harmlessly with
reactive oxygen species (also known as free radical oxygen).
Furthermore, scientists have shown that cocoa polyphenols act
as antioxidants in the human body! The polyphenols also had
additional beneficial effects on cardiovascular (i.e. heart)
health. All good reasons to eat chocolate!
C
H
C
C
C
C
H
C
C
H
2
C
H
C
H
O
C
C
H
C

21. C
H
C
H
C
O
H
O
H
H
O
O
H
O
H
C
H
C
C
C
C
H
C
C
H
2
C
C
H
O
C
C
H
C
C
C

22. H
C
O
H
O
H
H
O
O
H
O
H
O
H
H
C
H
C
C
H
C
H
C
H
C
O
H
H
C
C
C
H
C
C
H
C

23. O
H
O
H
H
O
H
C
C
C
H
C
H
C
H
C
H
O
O
H
e
p
i
c
a
t
e
c
h
i
n
e
p
i
g
a

24. l
l
o
c
a
t
e
c
h
i
n
p
h
e
n
o
l
p
h
e
n
o
l
i
c
c
o
m
p
o
u
n
d
s
P

25. o
l
y
p
h
e
n
o
l
s
a
r
e
m
a
d
e
f
r
o
m
p
h
e
n
o
l
i
c
c
o

26. m
p
o
u
n
d
s Figure 30.5. Phenolic compounds and polyphenols found in
cocoa.
7. Why is chocolate (a high fat food derived from a plant) a
solid at room temperature when most plant derived fats are
liquid oils?
8. Based on the structures of caffeine and theobromine, why
does it make sense that both are stimulants of the central
nervous system?
9. What type of “eating chocolate” (i.e. sweet dark chocolate,
milk chocolate or white chocolate) is going to have the highest
concentration of caffeine and theobromine and other
psychoactive molecules? (i.e. what type of chocolate should you
eat right before that tough final exam!)
10. Scientists at the University of Scranton have “discovered
that in hamsters, cocoa powder at a dose equivalent to two dark
chocolate bars per day significantly inhibited atherosclerosis, a
type of heart disease in which fat clogs up arteries, and raised
the levels of good cholesterol.”
a. Chocolate has high levels of saturated fat. Why does this not
contribute to cardiovascular (i.e. heart) problems?
b. What molecules in chocolate are responsible for the
beneficial cardiovascular effects?
Putting it all Together:
11. Chocolate is a high fat food – and since fats go rancid, most

27. high fat foods have a limited shelf life. However, chocolate has
a remarkably long shelf life for a food that is comprised of
mostly cocoa butter (fat). As we saw in Activity 11, rancid fats
arise from two sources – oxygen in the air causes oxidation of
the double bonds and water causes hydrolytic rancidity. Since
chocolate has little moisture, the most problematic type of
rancidity would be from oxygen in the air.
a. What is it about the chemical composition of chocolate
prevents oxidation of the fats?
b. What type of typical “eating” chocolate would be most
capable of preventing this oxidation? What is the chemical
explanation for why?
c. Chocolate’s ability to combat oxidation of its fats is also
beneficial for human health. Explain why.
12. Your friend tried to make the following recipe for “Fudgy
Brownies” from yummly.com - but they didn’t turn out quite as
expected. The brownies were very dense and tasted less
chocolatey than your friend wanted. Here is her ingredient list.
Upon looking at the ingredients, you ask your friend – “what
kind of cocoa powder did you use?” Your friend responds, “I
forgot to buy cocoa powder at the store – so I used this Dutch
cocoa powder that I found here in the pantry”
Can you diagnose the problem? Why is the type of cocoa
powder so important to this particular recipe? What did NOT
happen as a result of the wrong cocoa powder being used?
¾ cup unsweetened cocoa powder
½ tsp baking soda
⅓ cup vegetable oil
½ cup boiling water
2 cups white

28. Sugar
1 tsp vanilla extract
⅓ cup vegetable oil
1 ⅓ cups all-purpose flour
¼ tsp salt
2 eggs
� See Activity 17_Browning for a lesson on Maillard reactions.
� Milk solids are dried milk protein and sugar
� Lecithin was discussed in Activity 12_Emulsions and
emulsifiers
� Activities 10 and 11 talk about the solid vs. liquid nature of
fats, as well as fat melting temperature.
� Food Fats and Oils, 9th edition. 2006. The Institute of
Shortening and Edible Oils. � HYPERLINK
"http://www.iseo.org/httpdocs/Publications/FoodFatsOils2006.p
df"
�http://www.iseo.org/httpdocs/Publications/FoodFatsOils2006.
pdf� Not every fatty acid is listed, so the numbers won’t add up
perfectly to 100%
� These fatty acids are part of triglycerides within the fat/oil.

29. � Dogs can suffer serious poisoning from chocolate candies,
which is perhaps evidence of the cacao bean’s powerful
chemical defenses against would-be predators.
Copyright © 2016 Wiley, Inc.
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