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PROTEINS The Science of Food What are Proteins? Amino Acids Essential amino acids Complimentary proteins Specific chemical properties (charge, hydrophic, hydrophilic) Amino acid chemistries give proteins their primary, secondary, tertiary structure Structure function relationships Biological roles of proteins Organization of Information- From Genetics to Protein 1. Proteins are made of amino acids. 2. The amino acids are chemically different and can occur in any order. (ate, eat, tea) 3. The amino acids chemically interact with each other to give the protein its shape and function. Essential Amino acids • There are eight amino acids that cannot • • • • • • • be produced by the human body. body Histidine, Isoleucine, Leucine, Lysine, Phenyl-alanine, lysine, methionine, threonine, Valine Complete proteins contain all the essential amino acids. acids Incomplete proteins lack one or more Complimentary proteins make up for each other’s deficiency. deficiency Beans lack methionine. methionine, Corn lacks lysine. lysine Other complimentary proteins: Soybean & sesame, Rice and black-eyed peas Peptide bonds and Primary Structure Protein measurement- measure # of amino ends. Protein adulteration- add melamine, many amino ends. Secondary structure Alpha helix Beta Pleated Sheet Tertiary structure The overall conformation that arises from the secondary structure Show chain demonstration Do protein denaturation demonstration Start attendance sheets Conventional Wisdom, The “Central Dogma of Biology” DNA makes RNA makes (only one) Protein. Corollary: Only DNA can transmit information. (Proteins store that information.) Stanley B. Pusiner Puisner discovers prions! Human TSEs include Creuzfeldt-Jacob disease (CJD), Familial fatal insomnia (FFI), Kuru, and Gerstmann-Straussler-Scheinker disease (GSS). Animal TSEs (aka “Mad Cow”) Stanley B. Pusiner, 1997 Nobel Prize Biological Functions of Proteins • • • • • • • • Catalysis - enzymes Movement –actin, myosin, trypomysin Antigens Antibodies Toxins Structure –collagen, Keratin Transfer – Iron, O2 Actin and Myosin The muscles in your body are made of the proteins actin and myosin. The use a combination of Ca2+ and ATP to contract and release. The muscles in a body will under go rigor mortis once there is no energy going through them. (Tenderization) Functions of Proteins in Foods • Precipitation – loss of solubility (milk, casein, para-kapppa casein – denaturation) • Flocculation –aggregation without denaturation, clarification • Coagulation – internal self association • Gelatinization- ordered self association Functions of Proteins in Foods • Emulisfication • Dough formation • Color and flavor formation • Water binding, foaming, viscosity Proteins and Nutrition 4 Cal/gram Protein Quality = Protein Efficiency Ratio P.E.R = weight gain in rat per gram of protein Food P.E.R Eggs 3.5 Milk 2.7 Beef 2.6 TVP 1.7 Peanut Butter 1.5 White Bread 0.8 Corn Chips 0.5 Meat: 10-20 pounds feed 1 pound beef Poultry: 1.5 pound feed 1 pound poultry Meat has 15-20% protein, 5-40% fat, rest water Meat: 10-20 pounds feed 1 pound beef Poultry: 1.5 pound feed 1 pound poultry Meat has 15-20% protein, 5-40% fat, remainder is water Protein Requirements Person Requirement Adult male 56g Adult female 46g Lactating female 70g Average American 90g Athletes need more. 4:1 carb:protein Enzymes Make reactions go faster Have no side products Are highly specific Natural – no one has ever chemically synthesized an enzyme Work at relatively low temperatures “Gentle” Enzymes in Foods Enzyme Action “Naturally” In food processing Amylase glucoamylase Breaks down starch to glucose Saliva, barley malt, “softening” Makes fermentable sugars for bakers and brewers, Aids moisture retention, Clarification of liquids Invertase Breaks down sucrose to glucose and fructose Yeast Chocolate covered cherries Pectinase Breaks down pectin to glucoromic acid Fruit softening Clarification, improved pressing yields, separation of mandarin orange segments Glucose Isomerase Turns glucose in fructose Microbial High-fructose corn syrup Proteases Breaks up proteins into amino acids “proteolytic spoilage” of meat and fish Meat tenderization, chill-proofing of beer, Production of protein hydrolysates, texture, dough rheology papin Pineapple Enzymatic Reactions in Foods Lipases break down triglycerides to mono and diglycerides Polyphenol oxidase causes the natural browning of foods Summary of Proteins •The information in genes is translated into a specific sequence of amino acids. •The information in the amino acid sequence determines the protein’s secondary, tertiary, sequence and ultimately functions. •Diverse functions of proteins nutrition movement functions in food enzymes