2. Lipids: Nature’s Flavor Enhancers
Chapter 10
Lipids: Nature’s Flavor Enhancers

3. Objectives
Describe the molecular structure of glycerides, phospholipids, and sterols.
Define saturated, monounsaturated, and polyunsaturated fatty acids.
List categories of lipids based on physical state and dietary sources.
Relate physical characteristics of lipids to their performance in foods.
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4. Objectives Examine the functions of lipids in food preparation.
Analyze the nutritional impact of lipids in the diet.

5. Chemical Structure of Lipids
Lipids are organic compounds that are insoluble in water and have a greasy feel
They contain carbon, hydrogen, and oxygen
They differ from carbohydrates in chemical structure and function in food products
The 3 types of lipids found in food and in the human body are
triglycerides, phospholipids, and sterols

6. The Glycerides Glycerides have 2 basic parts
The base is a glycerol molecule with 3 hydroxyl groups that easily react with other compounds
Fatty acids are carbon chains with a carboxyl group (COOH) at one end
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7. The Glycerides
The carboxyl group of a fatty acid will readily react with a hydroxyl group of a glycerol producing a lipid and water
Glycerol can join with a
monoglyceride—glycerol with one fatty acid
diglyceride—glycerol with 2 fatty acids
triglyceride—glycerol with 3 fatty acids
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8. The Glycerides
When the positive carboxyl group on a fatty acid joins with the negative hydroxyl group on a glycerol, the polar ends combine, resulting in a nonpolar lipid
Mono- and diglycerides are partially soluble in water and soluble in fat
They are added to processed foods to keep mixtures of water and fats stable

9. Phospholipids
A phospholipid is a glycerol base with 2 fatty acids and a phosphorus-containing acid attached
Fatty acids dissolve in fat and the phosphorus-containing acid dissolves in water
Phospholipids are important because they
are part of cell membranes and help transport fats in and out of cells
help fats stay mixed in water-based solutions

10. Sterols
Sterols are complicated molecules that are derived from lipids and include
vitamin D
steroid hormones, including sex hormones
cholesterol, a part of every cell
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11. Categories of Lipids Based on Molecular Structure
First consideration ̶ how saturated the carbon chains are with hydrogen atoms
can form zero, one, or many double bonds
Fatty acids that
have the maximum number of hydrogen atoms are saturated
do not have the maximum hydrogen atoms possible are unsaturated
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12. Categories of Lipids Based on Molecular Structure
Monounsaturated fatty acids have one double bond
found in olive and canola oils, almonds, and walnuts
Polyunsaturated fatty acids have 2 or more double bonds
found in safflower, sunflower, and corn oils
Most lipids contain both types of fatty acids

13. Categories of Lipids Based on Physical State
Fats are solid at room temperature
butter, margarine, and shortening
Oils are liquid at room temperature
vegetable oils
The number of carbon and hydrogen atoms determine the temperature a lipid will liquefy
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14. Categories of Lipids Based on Physical State
Double bonds lower the temperature at which a lipid becomes solid
The melting point of a lipid is the temperature at which all the different fats and oils it contains are liquid
Each type of lipid has a different melting point
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15. Categories of Lipids Based on Physical State
Hydrogenation is the process of adding hydrogen atoms to an unsaturated lipid to increase its saturation level
Hydrogen is bubbled through liquid oil in the presence of a nickel catalyst
Double bonds in the fatty acid chain break and pick up extra hydrogen atoms
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16. Categories of Lipids Based on Physical State
Hydrogenation makes oils solid at room temperature
Advantages of hydrogenation include
longer shelf life than oil or lard
greater stability and lower production costs than lard
faster dissolving and setting properties in chocolate production

17. Categories of Lipids Based on Dietary Sources
Milkfats contain short chain fatty acids and come from cows, goats, and sheep
Lauric acids are lipids found in the oils of fruits and seeds from tropical palm trees
Vegetable butters come from seeds of tropical plants
Cocoa butter is the best known
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18. Categories of Lipids Based on Dietary Sources
Oleic-linoleic acids come from corn, peanuts, sunflowers, olives, and cottonseeds
Linolenic acid is found in soybeans and wheat germ and requires refrigeration
Animal fats are found in meats and poultry as seen by the marbling of meat
Marine oils are unsaturated oils from fish

19. Physical Characteristics: Melting and Solidifying
Lipids melt and solidify over a temperature range because of the mixture of fatty acids
The solidification point is the temperature at which all lipids in a mixture are in a solid state
The more saturated the fatty acid and the longer the length of the carbon chain, the higher is the melting point

20. Physical Characteristics: Nonpolar Molecules
Equal or balanced sharing of electrons means lipid molecules are nonpolar
Water, a polar molecule, will not mix with oil
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21. Physical Characteristics: Tendency to Deteriorate
Auto-oxidation is a complex chain reaction that starts when lipids are exposed to oxygen and results in deterioration
Rancidity is a form of food spoilage that poses no short term health risks and can be prevented by vacuum sealing or adding antioxidants to lipids

22. Functions of Lipids in Food Preparation
1. Lipids transfer heat from cooking utensils to food quickly, evenly, and at high temperatures
Smoke point is the temperature at which fatty acids break apart and produce smoke
Flash point is the temperature at which lipids will flame
Temperature is crucial to cooking food thoroughly without burning while deep frying
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23. Functions of Lipids in Food Preparation
2. Lipids tenderize baked products
Fats shorten flour’s protein strands, which cause chewiness and toughness
Fat to flour ratio determines flakiness
Lipids with high melting points work best for biscuits, pies, and puff pastry
Oils can be used in quick mix batters for products like pancakes, muffins, and waffles
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24. Functions of Lipids in Food Preparation
3. Lipids aerate batters
Aeration is the addition of air
Saturated fats allow tiny air pockets to form when beaten
Creaming fat and sugar together in cake recipes aerates the batter
Whipped margarine is an aerated form of margarine
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25. Functions of Lipids in Food Preparation
4. Lipids enhance flavors of other foods
Much of the flavor in food is due to the addition of salt, sugar, and fats
Common lipids that season foods are butter, margarine, and mayonnaise
Fats dissolve and disperse flavor compounds
Cottonseed oil is one of the most flavorless oils, followed by vegetable shortening and soybean and canola oils
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26. Functions of Lipids in Food Preparation
5. Lipids lubricate food components
This makes meat easier to chew as fat content increases
Greasy texture feels slick and smooth, making foods seem moister
Spreads like butter, margarine, and mayonnaise make sandwiches seem moister without making bread soggy
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27. Functions of Lipids in Food Preparation
6. Lipids serve as liquids in emulsions
An emulsion is a mixture of a lipid and a water-based liquid
Phospholipids stabilize emulsions because they have a polar end that attracts water and a nonpolar end that attracts the lipid
Examples are butter, margarine, mayonnaise, and bottled salad dressings

28. Lipids in Your Diet Lipids are necessary for a healthful diet
Lipids functions in the body to
provide a concentrated source of energy
give a longer feeling of fullness due to digestion time
help regulate body temperature
provide an energy reserve from lipids stored in adipose tissue
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29. Lipids in Your Diet Lipids functions in the body to
protect vital organs from injury
participate in cell production
transport vitamins A, D, E, and K
produce hormones, vitamins, and other secretions
provide essential fatty acids

30. Essential Fatty Acids
Lipids contain essential fatty acids for growth and development that the body needs, but cannot produce
Linoleic acid is found in corn, cottonseed, and soybean oils, as well as chicken
Linolenic acid is found in canola and soybean oils, walnuts, and fish

31. Omega-3 Fatty Acids
These are essential fatty acids that may help slow the growth of plaque in arteries
The Dietary Guidelines for Americans recommend 8 ounces or more per week of fatty fish such as tuna, salmon, and sardines
Alpha-linolenic acid from canola oil, flaxseed, and walnuts can become an omega-3 fatty acid in the body

32. The Role of Cholesterol
The body uses cholesterol to produce hormones and build cell membranes
Cholesterol is found in animal products
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Excess blood cholesterol leads to plaque buildup in arteries, or atherosclerosis
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33. The Role of Cholesterol
Cholesterol is transported through the body by lipoproteins
Low-density lipoproteins (LDL) carry cholesterol to the liver
High-density lipoproteins (HDL) find unneeded cholesterol and return it to the liver
High levels of LDL means a higher risk of developing atherosclerosis
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34. The Role of Cholesterol
To help keep LDL and HDL at healthy levels, recommendations include
limiting saturated fat and cholesterol intake
exercising regularly
maintaining a healthy weight
reading food labels carefully, especially for fat-free, low-fat, and cholesterol-free options as they may have added salt and sugar

35. Dietary Recommendations
To reduce the risk of heart disease
consume 20%–35% of daily calories from fat, mainly from polyunsaturated and monounsaturated fatty acids
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36. Recap Lipids are organic compounds insoluble in water
The 3 general types of lipids are
triglycerides, phospholipids, and sterols
Lipids can be categorized by
molecular structure
physical state
food sources from which they come
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37. Recap
Physical characteristics that impact the way lipids perform in food products are the
differing melting and solidification points
nonpolar nature of lipid molecules
tendency to deteriorate
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38. Recap Lipids serve 6 main functions in food preparation transfer heat
tenderize
aerate
enhance flavor
lubricate
create emulsions
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39. Recap Lipids function in the body to
provide a concentrated source of energy
regulate body temperature
protect vital organs
help produce body cells
transport fat soluble vitamins
produce hormones, vitamins, and other secretions
provide essential fatty acids
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40. Recap
Most fats in the diet should come from unsaturated fatty acid sources such as olive and canola oils, nuts, seeds, and fish
A fat-free diet does not provide the essential fatty acids needed for new cell growth and other body functions