1. Chapter 5 - LIPIDS
Triglycerides,
Phospholipids,
and Sterols

2. TYPES OF LIPIDS
1. Triglycerides
2. Phospholipids
3. Sterols

3. TRIGLYCERIDES
 Triglycerides – Fats & Oils
1. Predominate form of fat in foods
and major storage form of fat in
the body
2. Structure – composed of 3 fatty
acids + glycerol

4. Fatty Acids
 Organic acid (chain of carbons with
hydrogens attached) that has an
acid group at one end & a methyl
group at the other end
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5. Fatty Acids & Triglycerides
 glycerol + 3 fatty acids 
triglyceride + H2O
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6. FATTY ACIDS
 Fatty Acids – carbon
chains, vary in:
1. Length – affects
absorption
2. Saturation –chemical
structure; affects
cooking & storage
properties and health

7.  Length of carbon chain
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Stearic acid – 18-carbon, saturated
Simplified structure

8. FATTY ACIDS
Saturation
 Saturated fatty acid – carbon chains
filled with hydrogen atoms (no C=C
double bonds)
1. Saturated fat – triglyceride
containing 3 saturated fatty
acids, such as animal fats
(butter, lard) & tropical oils
(palm, coconut)
2. Appear solid at room temperature

9. FATTY ACIDS
 Unsaturated fatty acid – carbon chains
lack some hydrogens (>1 C=C double bond)
1. Monounsaturated fat – triglyceride
containing fatty acids with 1 double
bond; i.e. canola & olive oil
2. Polyunsaturated fat- triglycerides
containing a high % of fatty acids with
>2 double bonds; i.e. corn, safflower,
soybean, sunflower oils and fish;
3. Appear liquid at room temperature

10. Oleic acid – 18-carbon, monounsaturated
Linoleic acid – 18-carbon, polyunsaturated

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12. Fatty Acids
 Location of double bonds
 Omega number – refers to the
position of the double bond
nearest the methyl (CH3) end of
the carbon chain
 Omega-3 fatty acid
 Omega-6 fatty acid
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Omega-3 and Omega-6 Fatty Acids Compared

14. FATTY ACIDS
 Hydrogenated – addition of
hydrogen to unsaturated fat
1. Makes it more “solid” or firm
2. Effects stability and protects
against oxidation; more “shelf-
stable”
3. Widely used by food industry in
margarine, shortening, peanut
butter, baked goods & snack food

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Hydrogenation

16. Hydrogenation
 Cis vs. trans-fatty acids
 In nature, most double bonds are
cis meaning that the hydrogens
next to the double bonds are on
the same side of the carbon chain
When a fat is partially
hydrogenated, some of the double
bonds change from cis to trans

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Cis- and Trans-Fatty Acids Compared

18. PHOSPHOLIPIDS
 Phospholipids – similar to
triglycerides in structure
except only 2 fatty acids +
choline
Phospholipids in foods:
Lecithin, egg yolks, soybeans,
wheat germ, peanuts

19. Lecithin
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20. Phospholipids
1. Functions: part of cell
membranes and acts as
an emulsifier (helps
keep fats in solution)
2. Not a dietary essential;
made by the liver

21. Phospholipids
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22. Sterols
Structure
consists of
carbon rings
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Thomson Learning

23. STEROLS
 Important part of:
1. Sex hormones – testosterone
2. Vitamin D
3. Bile (aids fat digestion)
4. Adrenal hormones - cortisol
5. Cholesterol – in foods and
made by the liver; dietary
sources include egg yolks,
liver, meats, dairy products

24. Fat Digestion
 Hydrolysis
 Triglycerides 
monoglycerides, fatty acids,
glycerol
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25. Fat Digestion
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26. Fat Digestion
 Mouth
 Melting
 Lingual lipase
 Stomach
 Churning and mixing
 Gastric lipase
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27. Fat Digestion
 Small intestine
 Pancreatic lipases
 Intestinal lipases
 Small intestine
 CCK
 Bile and emulsification

28. Emulsification of Fat by Bile
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29. Fat
Digestion
Overview
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30. Lipid Transport
 Lipoproteins – clusters of lipids and
proteins that are used as transport
vehicles for fat
 Chylomicrons
 VLDL = very-low-density
lipoproteins
 LDL = low-density lipoproteins
 HDL = high-density lipoproteins
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31. Size & Compositions of Lipoproteins

32. Functions of Fats
 In the body, fats provide:
1. Energy – 9 kcals/gm
A. Supplies 60% of body’s energy
needs at rest
B. Stored as adipose tissue
2. Insulation & protection
3. Cell membrane constituents

33. Functions of Fats
 In foods, fats:
1. Provide energy (9 kcal/gm)
2. Contribute flavor, aroma, and tenderness
3. Provide satiety
4. Carry fat-soluble vitamins (A,D,E &
K)
5. Provide a source of essential fatty acids

34. Fatty Acids
 Essential fatty acids – 2 polyunsaturated
fatty acids that must be provided in diet
1. Linoleic – omega-6 fatty acid and
Linolenic – omega-3 fatty acid
2. Founds in plant oils, nuts, seeds, whole
grains and fish
3. Play a role in normal growth &
development and may prevent heart
disease, hypertension, arthritis &
cancer

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36. Health Effects of Fats
 Excess fat intake contributes to many diseases
including:
1. Obesity
2. Diabetes
3. Cancer
4. Heart disease
 How?
1. High fat diets = high kcal diets
2. High saturated fat intake raises blood
cholesterol
3. High fat intakes may promote cancer

37. Health Effects of Lipids
 Risks from trans fats
 Risks from cholesterol
 Risks from saturated fats
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38. Saturated Fats in the U.S. Diet

39. Dietary Cholesterol
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40. Health Effects of Lipids
 Benefits from monounsaturated
fats and polyunsaturated fats
 Benefits from omega-6 and
omega-3 fats
1. May reduce blood cholesterol
& help prevent cancer
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41. Dietary Recommendations
1. Limit total fat intake to <30% of kcals
Example: If 2000 kcal diet, then
2000 x .30 = 600 kcals/9 kcals per gram =
65 gms of protein
2. Limit cholesterol to <300 mg/day
3. Saturated & polyunsaturated fats each
<10% of kcals

42. Cutting Fat Cuts Calories and Saturated Fat
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43. Dietary Recommendations
1. Use all fats in moderation
*1 tsp fat = 5 gm = 45 kcals
2. Beware of “hidden fats” – added to
convenience foods, processed foods, & in cooking
3. Choose lean meats, skinless poultry,
nonfat dairy products; limit meats to <7 oz./day
4. Choose fish 2-3 times/week
5. Choose monounsaturated fats – canola, olive,
peanut, or sesame oils; avoid hydrogenated oils
6. Limit egg yolks to 3-4/week

44. Heart-Healthy Choices
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47. Comparing Butter & Margarine Labels

48. Fat Substitutes
 Types:
1. Carbohydrate based – i.e. Oatrim &
Z-Trim; made from plant fibers
2. Protein based – i.e. Simplesse; made
from egg white or milk protein
3. Fat based – i.e. Olestra; made from
sucrose & fatty acids; passes through
body undigested

49. Fat Substitutes
 B. Do they work?
1. Potential health benefits – promote
weight loss and lower blood lipids
2. But like sugar substitutes, many people
just eat more instead of replacing fat
3. Side effects possible with Olestra
4. Use in moderation