Download Protein in Foods

Chapter 17-Part 2
Variety of sources
 Eggs
 Meat
 Fish
 Poultry
Other Sources of Proteins
• Fruits
• Vegetables
• Grains
• Nuts
(They just do not have as
many amino acids)
Eggs
Contain almost every vitamin
and mineral you need
Yolks are rich in:
-iron
-phosphorus
-vitamin A
-several B vitamins
Lacking:
-vitamin C
-calcium only present in
the shells
Proteins in Eggs
 Protein is the foundation of an egg.
 Shell contains protein molecules interwoven with calcium
carbonate crystals.
Structure of an egg
Air Pocket
Egg
Membrane
Thin albumen
Yolk
Thick albumen
Chalaza
Shell membrane
Cracking open an egg you
first encounter
albumen (egg white) – makes up 54% of the
inner contents of an egg, known for
ovalbumin, a major protein in egg white.
Thickest part of the albumen is the
Chalaza – a twisted ropelike structure that keeps the egg yolk
centered.
Last part of the egg to
coagulate and may
remain slightly watery.
 Yolk – main components include
 Globular protein livetin
 High and low-density lipoproteins
 Contains all of the fat, along with most of the
other nutrients
Effects of Storage
Where should eggs NOT be stored in a refrigerator?
Why?
It exposes eggs to light and temperature every time you open
the door.
It hastens chemical changes that ultimately deteriorates the egg.
 How can you tell if an egg is fresh?
http://www.youtube.com/watch?v=9aytZn9cFgE
Meat
 Refers to any edible
portion of mammals,
 Including muscle and fatty
tissue
 Muscle tissue - Lean part of meat
 About 15-20% protein
 Other components include
Water, fat and minerals
 Muscle is composed of
 Fibrous proteins called actin and myosin
 They form bundles of fibers , held together by
connective tissues made of collagen and elastin
Two proteins with long, strong molecules.

Fish
 Shorter, segmented muscle
fibers are layered between
thin sheets of connective
tissue
Nuts and Legumes
From plants nuts and legumes
(dry deans, peas, lentils,
soybeans
Nuts – peanuts, walnuts
cashews
Carry a rich source of
nutrients
 Cholesterol-free
 Range in fat from
 Zero to very high
 Nuts too high in fat to be considered a main source of protein
 Soybeans are composed of 40% protein, their protein is equal
to that of foods from animals.
Emulsifiers – egg yolk, the
most common emulsifier
 Protein can stabilize oil-
and-water mixture
 Certain proteins contain
amino acids that are polar.
 One end of these amino
acids is attracted to water
while the other end avoids
water and bonds to oil.
Foams
 Air bubbles incorporated
and trapped in a protein
film by whipping.
 Add volume and lightness
 Begins when a proteincontaining liquid is
whipped.
 Whipping introduces air
and denatures the protein
molecules
 Air bubbles incorporated and
trapped in a protein film by whipping.
 Add volume and lightness
 Begins when a protein-containing liquid is whipped.
 Whipping introduces air and denatures the protein molecules