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

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 unsaturated continued

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 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 continued

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 continued

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 continued

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 continued

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 continued

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

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 ©rob3000/Shutterstock.com Excess blood cholesterol leads to plaque buildup in arteries, or atherosclerosis continued

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 continued

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

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

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 continued

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 continued

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

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 continued

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