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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
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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
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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