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NHM 253 Lecture 3

by: Regan Dougherty

NHM 253 Lecture 3 NHM 253

Regan Dougherty
GPA 4.0

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Lecture Notes from Feb 2
Food Science
Dr. Crowe
Class Notes
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This 4 page Class Notes was uploaded by Regan Dougherty on Tuesday February 2, 2016. The Class Notes belongs to NHM 253 at University of Alabama - Tuscaloosa taught by Dr. Crowe in Fall. Since its upload, it has received 55 views. For similar materials see Food Science in Nutrition and Food Sciences at University of Alabama - Tuscaloosa.

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Date Created: 02/02/16
Tuesday, February 2, 2016 NHM 253 Lecture 3 Food Composition and Chemistry Part II - Lipids • 2 Groups of Lipids: - Fats • source: animals • Fats are usually saturated. • solid at room temperature - Oils • source: plants • Oils are usually unsaturated. • liquid at room temperature - Fats and oils differ in source, state, and saturation. • Lipids are insoluble in water. • Triglycerides are the most common form of edible lipids. - Formation of a triglyceride: • glycerol backbone (contains hydroxyl groups) • 3 fatty acids connected to the backbone - The fatty acids can differ. • 3 water molecules are released when the fatty acids bond to the glycerol backbone. Saturation • - Saturated - all carbons ar bonded to 2 carbons and 2 hydrogens • Saturated fats (MEMORIZE): meat, poultry, milk/butter/cheese, egg yolk, lard, chocolate, coconut/coconut oil, palm oil, vegetable shortening 1 Tuesday, February 2, 2016 - Unsaturated - one or more double bonds are present between carbons due to an absence of hydrogen(s) • Monounsaturated - only one double bond - MEMORIZE: avocado, peanuts/peanut butter, olives/olive oil • Polyunsaturated - more than one double bonds - MEMORIZE: vegetable oils (corn, safflower, soybean, sunflower, canola, etc.), margarine, mayonnaise, certain nuts (almonds, pecans, walnuts) - Lipids with a greater number of double bonds are more easily oxidized (have a shorter shelf life). - Lipids with a greater number of double bonds adhere less easily to artery walls. - Free radical - contains an unpaired electron in its outermost shell (it is unstable) • Lipids are the most easily oxidized molecule in food and in the body. • If a lipid becomes a free radical, it loses a lot of its nutritive value. - It smells bad. - It seeks to “steal” an electron from another lipid (forming another free radical). • Free radicals form due to over-exposure to light, heat, and oxygen. • Phospholipid - glycerol backbone + 2 fatty acids + phosphate group - It is a triglyceride that is missing a fatty acid (and that fatty acid is replaced by a phosphate group). - Ampiphilic - both hydrophilic and hydrophobic properties - Phospholipids are found in liquid foods that contain fats because they act as emulsifiers. - Phospholipids are found in cell membranes. - All phospholipids are lipids. But not all lipids are phospholipids. • Functions of Lipids in Food - heat transfer - aid in tenderization of foods 2 Tuesday, February 2, 2016 - texture and mouthfeel - flavor and satiety - phospholipids act as emulsifiers - Food Proteins • composed of amino acids joined by peptide bonds • contain C, H, O, and N exhibit primary, secondary, tertiary, and quaternary structures • - Primary - amino acids linked together - Secondary - 2 long amino acid chains - Tertiary - 2 amino acid chains “crumpled” up (3D) - Quaternary - multiple tertiary proteins (has a hydrophobic core) - Proteins in food primarily exist in the tertiary and quaternary forms. • Protein Denaturation - Denaturation is important for taste. - Chemical denaturation • Food-grade acids break down proteins. - ex. lemon juice, orange juice, vinegar, coffee, Sprite/Coke (carbonic acid) • Enzymes break down proteins. - Physical denaturation - exposure of proteins to heat • ex. cooking food - Mechanical denaturation - stress applied to protein • ex. pounding meat, cutting meat, tenderization • Functions of Proteins in Food - hydration - ability of protein molecules to attract and bind water • Some amino acids are polar (they are the ones that allow for the water-binding capacity). 3 Tuesday, February 2, 2016 • Allows proteins to thicken foods, form gels, etc. - emulsification due to amphiphilic nature • If a protein has polar and nonpolar amino acids, it can serve as an emulsifier. - buffering - protein molecules aid in resisting extreme pH shifts in food products - browning - two basic types of browning reactions • enzymatic - Causes loss of nutritive value • non-enzymatic - ex. Maillard reaction - color development in the browning of meat, roasted coffee, chocolate, some baked goods, fried foods. reactants are nitrogen in the amino acids, some sugars, and water • • slightly sweet with a robustness of other flavors • There are actually 3 types of browning of foods. The other is caramelization (browning of sugar, provides sweet taste). - enzymes - catalysts that speed up the rate of a biochemical reaction without getting destroyed in the process • All enzymes are proteins, but not all proteins are enzymes. • Enzymes in Food Production - adding pectinases to fruit juices to clarify the juice - producing high fructose corn syrup from cornstarch - adding rennin to milk to cause the milk proteins the coagulate • Enzymatic browning - polyphenol oxidase (PPO) catalyzes the oxidation of phenols into brown-colored melanin - Phenols - have antioxidant activity 4


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