Chapter 17-Part 2

PROTEIN IN FOODS

Variety of sources

EggsMeatFishPoultry

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 vitaminsLacking:

-vitamin C-calcium only present in the shells

Proteins in EggsProtein 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 includeGlobular protein livetinHigh and low-density lipoproteinsContains all of the fat, along with most of the other nutrients

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.

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 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.

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-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.

Protein in Cooking

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 protein-containing 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 lightnessBegins when a protein-containing liquid is

whipped.Whipping introduces air and denatures the

protein molecules