Chapter 10
Lipids are a category of organic compounds that are insoluble in
water and have a greasy feel.
There are three types of lipids with unique chemical structures:
The Glycerides:
• Monoglycerides
• Diglycerides
• Triglycerides
• Phospholipids
• Sterols
•
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The core of lipids is the
glycerol molecule.

Molecules that have a
glycerol base are called
glycerides.
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Fatty Acids are organic
molecules that consist of
a carbon chain with a
carboxyl group at one
end.
A carboxyl group is a
carbon atom, two
oxygen atoms, and a
hydrogen atom.
The carboxyl group of a
fatty acid will readily
react with a hydroxyl
group of glycerol.
Monoglyceride
One fatty
acid
attached
at the site
of a
hydroxyl
group.
Diglyceride
A glycerol
with two
fatty acids
attached at
the site of a
hydroxyl
group.
Major type of fat
found in foods and
in the body.
A glycerol
with a fatty
acid
attached at
each of the
three
hydroxyl
sites.
Triglyceride
•
•
•
Can have 3 different fatty acids attached
20 fatty acids to choose from
Create different characteristics
• Cooking performance
• Shelf life
• Nutritional value
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Is a glycerol base with 2 fatty acids and a
phosphorus-containing acid attached.
The fatty acids are soluble in fats.
The phosphorus-containing acid is soluble in
water.
Allows to mix w/both water-based and fatbased substances.
Phospholipids help fats stay mixed in waterbased solutions
 Keep foods like mayonnaise from separating.


Are complicated molecules derived or made
from lipids.
They include:
 Cholesterol (most familiar b/c part of every cell in human body)
 Vitamin D
 Steroid hormones
Based on Molecular Structure
Based on Physical State
Based on Dietary Sources
See page 273 in textbook

Saturated: when fatty acids have the maximum number of
hydrogen atoms.
 Butyric:
 Stearic:
Unsaturated: when fatty acid does not contain all the
hydrogen atoms it could contain.
 Monounsaturated: fatty acids that have 1 double bond in
the carbon chain.

 Oleic:
 Erucic:

Polyunsaturated: Fatty acids have 2 or more double bonds
in the carbon chain.
 Linoleic:
 Linolenic:
See page 278 in textbook
One of the easiest ways to categorize lipids is by their
physical state at room temperature.
 Fats: lipids are solid at room temp.
 Oils: lipids are liquid at room temp.
 The #’s of hydrogen and carbon atoms on a fatty acid
chain determine the temp. at which lipids liquefy.

 More hydrogen = higher melting point
 More double bonds = lower melting point

The type of fatty acid present in the largest amount
has has greatest effect on characteristics of the lipid.
(see page 277 in textbook)

Melting point: temp. at which a substance changes from solid to liquid.
Hydrogenated Vegetable Oils

Hydrogenation: the process of adding hydrogen atoms to
an unsaturated lipid to increase its saturation level.
 Used to make oils solid at room temp
▪ Ex : margerine
 Achieved by bubbling hydrogen through liquid oil in the presence of a
nickel catalyst.

Advantages include:
 Longer shelf life than oil or lard
 Greater stability than lard
 Lower production cost than lard
 Faster dissolving and setting properties in chocolate production.
Triglycerides come from 7 main groups of dietary sources.
Milkfats:
Lauric Acids:
Vegetable Butters:
Oleic-linoleic acids:
Linolenic acid:
Animal Fats:
Marine Oils:
Differing Melting and Solidification Points
Nonpolar Molecules
Tendency to Deteriorate

Lipids do not have a specific melting point
because most lipids are mixtures of different
fatty acids.

Lipids will also become solids at different
temps.

Solidification point: the temp. at which all
lipids in a mixture are in a solid state.

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Lipid molecules have a equal or balanced
sharing of electrons, which makes them
nonpolar.
Nonpolar molecules readily mix with other
nonpolar molecules but do not want to mix
with polar molecules
 This is why water and oil do not mix.

Lipids are large molecules with spaces
between the parts of the molecules.
 This causes lipids to be less dense than water.
▪ Ex: oil floats on water

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Lipids have a tendency to react with oxygen.
Auto-oxidization: complex chain reaction that
starts when lipids are exposed to oxygen.
 Oxygen will bind to the lipid molecules and then to other
compounds. (domino effect)
 Starts to form other compounds and makes food rancid
(bad flavor, color, and odor)

Antioxidants: compounds that quickly react with
oxygen to form new substances.
 Will react with oxygen before lipids do.
▪ Ex: vitamins A,C, and E.
Transfer Heat
Tenderize
Aerate
Enhance Flavor
Lubricate
Serve as Liquids in Emulsions
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Excellent heat medium
Temp. of lipids will continue to increase as
heat is added.
Every lipid has a temp. at which the fatty
acids begin to break apart and produce
smoke. This temp. is called the smoke point.
Once oil starts to smoke, nothing should be
cooked in it, or it should be discarded,
because it will cause an unpleasant flavor.

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Flash point is the temperature at which
lipids will flame (this occurs around 600
degrees F).
Do not salt food until after deep frying
because it will lower the smoke point of the
oil, reducing the time the oil can be used.

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Tenderize baked goods
Protein in baked goods have long strands and
the lipids tend to shorten those strands.
 That is why the solid white fate sold for baking is
called shortening.
Fat to flour ratio will determine how flaky a
baked product.
 You cut in fats to dry ingredients and do not over
mix or the dough will not be suitable for baked
goods.

 Will become a greasy ball
Aerate
The addition of air into a batter.
Saturated fats allow tiny air
pockets to form when batters are
sufficiently beaten.
 Oils are not suitable for this
because they will separate from
the mixture.
 In cakes:
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 You cream the ingredients together
to aerate them. You cant heat them
too high because you don’t want
them to melt (then they act like oils).
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Fat is a major flavor enhancer.
Overeaten by most people in the U.S.
Used in preparation of many foods:
 Salad dressings, sauces, soups, casseroles, etc.

When you want to taste more of the main
food product and not the fat, use oils that
have very little taste
 Ex: soybean oil, canola oil, and sunflower oil.
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Makes meat easier to chew as the fat content
increases.
Pleasant mouth feel
Feel slick or smooth to the tongue
Foods seem moister
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An emulsion is a mixture that contains a nonpolar lipid and a water-based liquid, which is
polar.
Another compound with a polar and nonpolar
end must be added to emulsify
Phospholipids have this chemical structure
and create emulsions.
 Ex: mayo, phospholipid (lecithin) fount in egg
yolks, prevents oil from separating.
Carbohydrates Versus Fats
 Which is more fattening,
See page
289 in
textbook
100 kilocalories of
carbohydrates or 100
kilocalories of fat?
Functions of Lipids in the Body
Essential Fatty Acids
The Role of Cholesterol
Unsaturated Oils
Dietary Recommendations
Calorie Density
See page 293 in textbook