Images shutterstock.com Chapter 10 Lipids: Nature’s Flavor Enhancers

Images shutterstock.com

Chapter 10

Lipids:Nature’s Flavor

Enhancers

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.

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.

continued


Objectives

• Examine the functions of lipids in food preparation.

• Analyze the nutritional impact of lipids in the diet.


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


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

continued©Goodheart-Willcox Publisher

©Goodheart-Willcox Publisher


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

continued


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


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


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

©Goodheart-Willcox Publisher


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 unsaturatedcontinued


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


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

continued


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

continued


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

continued


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


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

continued


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


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


Physical Characteristics: Nonpolar Molecules• Equal or balanced sharing of electrons

means lipid molecules are nonpolar• Water, a polar molecule, will not mix

with oil

©SunnyS/Shutterstock.com


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


Functions of Lipids in Food Preparation1. 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 continued


Functions of Lipids in Food Preparation2. 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

continued


Functions of Lipids in Food Preparation3. 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

continued


Functions of Lipids in Food Preparation4. 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

continued


Functions of Lipids in Food Preparation5. 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

continued


Functions of Lipids in Food Preparation6. 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


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

continued


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


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


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


The Role of Cholesterol

• The body uses cholesterol to produce hormones and build cell membranes

• Cholesterol is found in animal products

continued

©rob3000/Shutterstock.com

• Excess blood cholesterol leads to plaque buildup in arteries, or atherosclerosis



• 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

continued



• 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


Dietary Recommendations

• To reduce the risk of heart disease– consume 20%–35% of daily calories from

fat, mainly from polyunsaturated and monounsaturated fatty acids

©yamix/Shutterstock.com


• 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

Recap

continued


• 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

Recap

continued


• Lipids serve 6 main functions in food preparation– transfer heat– tenderize– aerate– enhance flavor– lubricate– create emulsions

Recap

continued


• 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

Recap

continued


• 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

Recap

Documents

Images shutterstock.com Chapter 10 Lipids: Nature’s Flavor Enhancers