chapter 17-part 2
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Chapter 17-Part 2. Protein in Foods. WHERE DO THEY COME FROM?. Eggs Meat Fish Poultry. Variety of sources. 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. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 17-Part 2
PROTEIN IN FOODS
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Variety of sources
EggsMeatFishPoultry
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Other Sources of Proteins• Fruits• Vegetables• Grains • Nuts (They just do not
have as many amino acids)
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Eggs
Contain almost every vitamin and mineral you need
Yolks are rich in: -iron -phosphorus-vitamin A
-several B vitaminsLacking:
-vitamin C-calcium only present in the shells
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Proteins in EggsProtein is the foundation of an egg.Shell contains protein molecules
interwoven with calcium carbonate crystals.
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Structure of an egg Air Pocket
Egg
Membrane Thin albumen
Yolk Thick albumen
Chalaza
Shell membrane
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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.
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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.
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Yolk – main components includeGlobular protein livetinHigh and low-density lipoproteinsContains all of the fat, along with most of the other nutrients
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Effects of StorageWhere 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.
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How can you tell if an egg is fresh?http://www.youtube.com/watch?v=9aytZn9cFgE
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Meat
Refers to any edible portion of mammals,
Including muscle and fatty tissue
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Muscle tissue - Lean part of meatAbout 15-20% proteinOther components include
Water, fat and mineralsMuscle is composed of
Fibrous proteins called actin and myosinThey form bundles of fibers , held together by connective tissues made of collagen and elastin Two proteins with long, strong molecules.
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Fish
Shorter, segmented muscle fibers are layered between thin sheets of connective tissue
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Nuts and Legumes
From plants nuts and legumes (dry deans, peas, lentils, soybeans
Nuts – peanuts, walnuts
cashews
Carry a rich source of nutrients
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Cholesterol-freeRange in fat from
Zero to very highNuts too high in fat to be considered a main
source of proteinSoybeans are composed of 40% protein,
their protein is equal to that of foods from animals.
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Protein in Cooking
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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.
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Foams
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
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Air bubbles incorporated and trapped in a protein film by whipping.Add volume and lightnessBegins when a protein-containing liquid is
whipped.Whipping introduces air and denatures the
protein molecules