Chapter 17-Part 2 Protein in Foods

WHERE DO THEY COME FROM? Variety of sources Eggs Meat Fish Poultry 2

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 Egg Membrane Thin albumen Yolk Thick albumen 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

Nuts too high in fat to be considered a main source of protein 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.

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 lightness Begins when a protein-containing liquid is whipped. Whipping introduces air and denatures the protein molecules