Food Composition - Lipids and Proteins PDF

Food Composition Lipids ANSC 2053 Emilio Gutierrez, PhD Lipids – Fats and Oils Fats are solid at room temperature Usually derived from animal sources Oils are liquid Usually derived from plant sources Exceptions? Plant oils that are solid? Coconut oil Ani...

Food Composition Lipids ANSC 2053 Emilio Gutierrez, PhD Lipids – Fats and Oils Fats are solid at room temperature Usually derived from animal sources Oils are liquid Usually derived from plant sources Exceptions? Plant oils that are solid? Coconut oil Animal oils that are liquid? Fish oil Lipids – Fats and Oils Of all foods, fats have the highest caloric density. 9 calories/gram Contribute the most to the feeling of satiety after a meal. Lipids contribute unique mouthfeel and flavor to foods. Can be heated higher temperatures than the boiling point of water. Heat transfer  crispy crust textures Foods High in Lipids High in fats from animal sources: Examples: Meats, poultry, dairy products High in fats from plant sources: Examples:Nuts, seeds, avocado, olives, coconut Invisible fats: not easily observed in foods. Visible fats Vegetable oils, butter, margarine, shortening, lard, tallow Composition of Lipids Composed of carbon, hydrogen, and oxygen. Similar to what other nutrient type? How do we determine if a substance is a lipid? Solubility test; Acetic acid is the one lipid that will dissolve in water because its particle size/ molecule is so small. Edible Lipids – Classification Triglycerides (fats and oils) Phospholipids Sterols Edible Lipids – Triglycerides Fatty acids rarely found “free” in food 95% of lipids are triglycerides Three fatty acids attached to a glycerol molecule. Fatty acids can be identical (simple), or different (mixed) Fatty Acids Fatty acids can be differentiated in three ways: 1.Chain length (# of carbons) Usually even and can range from 2 to 20 Acetic acid is the shortest (2 carbons) 2.Degree of saturation (# of double bonds) No double bonds: saturated Double bonds: unsaturated 3.Type of double bond Trans and cis fatty acids Oleic acid is no double bond so saturated Linoleic acid is double bonded so is unsaturated Fatty Acids – Melting Point Chain length and melting point Saturated fatty acids of >10 carbons are solid at RT. Longer the chain the fattier the acid Degree of unsaturation affects the melting point The more unsaturated, the more liquid at RT. The more saturated, the firmer its consistency. High or low melting point? Vegetable oils Butter Chain Length Degree of Saturation Fatty Acids (FA) Most foods contain all 3 types of FAs, but 1 predominates 1. Monounsaturated: canola and olive oil, avocado 2. Polyunsaturated: most vegetable and fish oils 3. Saturated: animal fats, coconut and palm oils Polyunsaturated to saturated ratio (P:S) Animal origin: 50:50 Plant origin: 85:15 Fatty Acids Fatty Acids Approximately 40 FAs found in nature. Essential fatty acids- usually Polyunsaturated FA (PUFA) -Omega-3 (ω-3), omega-6 (ω-6) When consumed in moderate amounts ω-3: cognitive development, reduce inflammation, prevent heart disease. ω-6: regulate metabolism, skin and hair growth, and maintain bone health. Fatty Acids – Omega-3 and Omega-6 NOTE: Determine if a fatty acid is omega 3 or omega 6, count the number of carbons atoms that are in the methyl end to the double bond Fatty Acids – Cis and Trans Describes geometric shape of the fatty acid. Cis: hydrogens on the same side as the double bond. Trans: hydrogens on either side of the double bond. Cis and Trans Fatty Acids Most of the fatty acids in nature are in cis or slightly v-shaped configuration. Trans fats are naturally found in food products from ruminants. -like butter and cheese The presence of a trans double bond in an unsaturated fatty acid increases its melting point. Oleic (cis) and elaidic (trans) are both 18-carbon FAs. Oleic 14ºC Solid or liquid at RT? Elaidic 44ºC Trans Fatty Acids – Hydrogenation Unsaturated fatty acids can be made solid at RT through hydrogenation. Hydrogenation: addition of hydrogen atoms to an unsaturated fatty acid causing the double bonds to become single bonds (saturated). Turns vegetable oil into shortening. Shortening? -Any fat that is solid at room temperature. Examples? - Vegetable oil and lard Trans Fats – Hydrogenation Complete hydrogenation results in all double bonds being converted into single bonds. Partial hydrogenation makes the oils more stable and less likely to become rancid. -Can withstand heating and used fot long period of time Negative Effects? - Some double bonds change configuration from cis to trans -Trans fats are linked to coronary heart disease. Economical alternative to animal fats. Edible Lipids - Animal Sources Butter: high amount of saturated fat. Poultry: highest amount in the skin. chicken, turkey, duck, highest amount in skin Dairy products: major source of short-chain saturated FAs. Whole milk, ice cream, cheese, sour cream, yogurt, cream Edible Lipids - Animal Sources Processed meats: high amounts of saturated fat, high in calories, and low in nutritional value. Bacon, sausage, bologna Eggs: high saturated fat and cholesterol Where? Yolk or white? -The yolk Red Meats: medium and long chain saturated FAs. Steak, porterhouse, T-bone, sirloin, ribeye, filet, hamburger and ground beef Phospholipids Similar to triglycerides One fatty acid is replaced by a phosphate group. Makes the phospholipid hydrophilic. Fatty acid components are hydrophobic. -Can be Amphipathic molecules Important component of cells Cell membranes Sources of animal origin: egg and liver. Phospholipids – Food Uses Emulsifier: compound that possesses both hydrophilic and hydrophobic properties, so it disperses in either water or oil. - Helps mix the mixtures into one thing Lecithin most used phospholipid in the food industry. Source: egg yolk and soybean Used in beverages, baked goods, mayonnaise, and candy bars. Sterols Interconnected rings of carbon atoms with variety of side chain attachments. Many sterols are important in maintaining the human body Cholesterol Bile Sex hormones (testosterone, estrogen) Adrenal hormones (cortisol) Vitamin D Sterols - Cholesterol Cholesterol: most significant sterol in foods. NOTE: Both animal and plants contain sterols. Cholesterol only found in foods of animal origin Meat and poultry Fish Organ meats (brain, liver) Butter portion of dairy products Egg yolks Sterols – Cholesterol Sterols - Dietary vs Blood Cholesterol Do we need to pay attention to the cholesterol in foods? For years, dietary cholesterol was implicated in increasing blood cholesterol levels  elevated risk of CVD. 85% of blood cholesterol is made in the liver Not coming directly from food The biggest influence on blood cholesterol level is the mix of fats and carbohydrates in your diet. Not the amount of cholesterol we eat from food. Limit the amount of dietary cholesterol if you have diabetes or other metabolic conditions. Bad vs Good Cholesterol Cholesterol travels through the blood on proteins called lipoproteins. LDL (low-density lipoprotein) cholesterol: “bad” cholesterol Makes up most of the body’s cholesterol. ↑ LDL increases risk for heart disease and stroke. HDL (high-density lipoprotein) cholesterol: “good” cholesterol Absorbs cholesterol in the blood and carries it to the liver  discarded. ↑ HDL lower risk for heart disease and stroke. Bad vs Good Cholesterol Too much LDL cholesterol leads to “plaque” formation. Review Questions – Homework Food Composition Proteins Protein Greek word proteos of “prime importance” Body makes most necessary carbs and lipids, but it can only make about half of the compounds required for protein synthesis. What is needed to manufacture proteins?? Protein – Amino Acids Building blocks of proteins. 20 amino acids commonly found in proteins. 9 are essential for humans (10 for animals) Phenylalanine Histidine Valine Isoleucine Tryptophan Lysine Methionine Leucine Threonine ?? Proteins – Composition Proteins differ from carbohydrates and lipids. Proteins contain nitrogen atoms  “amino” Polymers of amino acids linked by peptide bonds. Amino acid characteristics drive protein folding. Protein structure determines function. Proteins – Structure Primary structure: most basic level of organization. Identified by the sequence of amino acids listed in order. Secondary structure: intramolecular hydrogen bonding between neighboring amino acids. Identified by the formation of helical or pleated structure. Tertiary structure: the secondary structure can be further folded into various configurations by the formation of different types of bonds. Identified as the 3D structure of a protein. Quaternary structure: association of multiple proteins and non- proteins structures to form a functional molecule. Protein Structure – Hemoglobin Protein – Synthesis How are proteins formed? Transcription Translation Proteins in the Body At least 100,000 different proteins in the human proteome. How many genes in the human genome? Fundamental component of tissues in animals and humans. Found in muscle, bones, skin, hair and virtually any other body part or tissue. Functions: structural, hormones, receptors, enzymes, carriers, metabolites, etc. Protein Requirements National Academy of Medicine says adults should get 0.8 grams of protein per every kilogram of body weight per day. 140-pound person  50 grams protein/day. 200-pound person  70 grams protein/day. Athletes?? Protein Quality in Foods Foods vary in protein content and quality. Complete: contains all the essential AAs in sufficient amounts for the body’s maintenance and growth. Most protein from animal sources. Incomplete: does not provide all the essential amino acids. Usually from plants Protein complementation? Protein Digestion No nutritional value until broken down Denatured in the stomach by HCl Broken down by enzymatic activity Proteases and peptidases End products Short peptides Amino acids Nitrogen and sulfur Protein Insufficiency or Excessive Protein Lack of sufficient protein can lead to severe metabolic diseases: Kwashiorkor- severe deficiency of protein Marasmus – severe deficiency of protein and energy Too much protein Overconsumption or excessive supplementation Hepatic and renal dysfunction Functions of Proteins in Foods Proteins are involved in a wide range of reactions that are responsible for the varied/characteristic color or texture of a food: Hydration Denaturation/coagulation Enzymatic reactions Buffering Browning Protein Functions – Hydration Ability of proteins to dissolve in and attract water. Gel formation Dough formation Gel formation: Protein strands attract water  firm structures. Milk, meat, egg Binders, stabilizers, and thickeners Used in preserves, confectioneries, and desserts Sausages Protein Functions – Hydration Bread making Water and milk mix with yeast and wheat proteins (gliadin and glutenin)  gluten. Gluten elastic qualities allow it to rise by the action of the CO2 produced by yeast fermentation. Protein Functions – Denaturation  Coagulation Denaturation: irreversible process by which the structure of a protein is disrupted, resulting in loss of function. Heat, extreme pH changes, alcohol, mechanic action Denaturation can result in coagulation. Clotting and precipitation of protein in a liquid into a semi- solid compound. Protein Functions – Enzymatic Reactions Enzymes combine with a substrate to catalyze (speed up a reaction) and release a product. Hydrolases, oxidoreductases, lyases, transferases, ligases, isomerases Enzyme structure Holoenzyme = protein portion of the enzyme + nonprotein portion (coenzyme or cofactor). Nonprotein portion necessary for activity Coenzymes are usually vitamins Cofactors are usually minerals Enzymes in the Food Industry Many foods on the market exist because of enzyme reactions Wines, cheese, corn syrups, yogurt, cottage cheese, baked good, sausages, juices, egg white replacers Rennin (cheese): milk into a curd Papanin, bromelanin, ficin: meat tenderization Polyphenol oxidase: dark color to tea, coffee, cocoa, and raisins Enzymes in the Food Industry Glucose oxidase: desugaring of eggs, flour, and potatoes. Salad dressing preparation. Baked products: used to prevent staling, improve flour and dough quality, bleach flour, and enhance crust color. Maltogenic amylase Used to improve filtration of beer. β-glucanase Enzymes in the Food Industry Activity influenced by pH and temperature Subject to denaturation Each has optimal pH and temp for operation. Most do best in 95°F-104°F with a neutral pH. Inhibit action of some enzymes Lipoxygenase activity in milk- produces off-flavors. Boiling fruits and vegetables may denature enzymes that cause spoilage. Pasteurization also halts enzyme activity. Enzymes in the Food Industry Quality testing Adequate pasteurization: measure phosphatase enzyme activity. Can be used to detect bacterial contamination in meat, poultry, fish, and dairy products. Enzymes in the Food Industry Enzymes are amphoteric. Capable of acting as an acid or base. Buffers: avoid extreme changes in pH Helps food keep appearance and structure for longer periods of time. Enzymes in the Food Industry Proteins play critical role in browning of foods 2 chemical reactions: Maillard Reaction (heat ~90ºC) Reaction between sugars and proteins  brown complexes Enzymatic Browning (oxygen, an enzyme, a phenolic compound) Tyrosinase oxidizes tyrosine  dark-colored melanin compounds Browning Review Questions – Homework