PROTEINS

The Science of Food

What are Proteins?Amino AcidsAmino Acids

Essential amino acidsComplimentary proteinsSpecific chemical properties (charge, hydrophic, hydrophilic)

Amino acid chemistries give proteins their primary, secondary, tertiary structure

Structure function relationshipsBiological 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

• Histidine, Isoleucine, Leucine, Lysine, Phenyl-alanine, lysine, methionine, threonine, Valine

• Complete proteins contain all the essential amino acids

• Incomplete proteins lack one or more

• Complimentary proteins make up for each other’s deficiency

• Beans lack methionine, Corn lacks lysine

• Other complimentary proteins: • Soybean & sesame, Rice and

black-eyed peas

• There are eight amino acids that cannot be produced by the human body.

• Histidine, Isoleucine, Leucine, Lysine, Phenyl-alanine, lysine, methionine, threonine, Valine

• Complete proteins contain all the essential amino acids.

• Incomplete proteins lack one or more

• Complimentary proteins make up for each other’s deficiency.

• Beans lack methionine. Corn lacks 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 structureThe overall conformation that arises from the

secondary structure

Show chain demonstrationDo 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/gramProtein Quality = Protein Efficiency Ratio

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

P.E.R = weight gain in rat per gram of protein

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

90gAthletes need more. 4:1 carb:protein

EnzymesMake reactions go fasterHave no side productsAre highly specificNatural – no one has ever chemically

synthesized an enzymeWork at relatively low temperatures“Gentle”

Enzymes in FoodsEnzyme 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 FoodsLipases break down triglycerides to mono and diglyceridesPolyphenol 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

nutritionmovementfunctions in foodenzymes