A. Describe ways in which protein is used in food preparation. b. Identify the essential and nonessential amino acids. c. Compare and contrast complete.

a. Describe ways in which protein is used in food preparation. b. Identify the essential and nonessential amino acids. c. Compare and contrast complete and incomplete proteins. d. Explain what happens during the

denaturation of protein and how the process occurs.

e. Explain coagulation and apply basic principles of the chemistry of

protein to cooking eggs, milk, and meat products and in creating egg foams and meringues.

Proteins have a role in both living organisms and in food productsPrimary food sources

Eggs, dairy products, meats, poultry, and fish Grain sources

Structural Protein is needed by every body cell.

Helps to replace and repair cells Most of the bodies hormones and enzymes

are largely proteins. Some proteins pick up, deliver, and store

nutrients in the cells. Antibodies (proteins) help ward off disease. Help to stabilize pH levels Proteins can supply energy but only when

the body is starved of carbohydrates (this is not good for the body)

These are large and complex & often called MACROMOLECULES (large molecules containing many atoms).

Protein molecules are made of the followingHydrogenCarbonOxygen NitrogenSometimes other elements* Nitrogen is not a component in other

nutrients ONLY PROTEIN

Protein molecules are made up of a chain of acids that contain carbon molecules called amino acidsThere are 20 amino acids in the human

body, and about 150 others found in plants and animals

Amino acids can be classified into two groups: essential and non-essentialThere are 20 AA’s found in the body

12 Non-essential AA’s can be made by the body

This leaves 8 essential AA’s that MUST BE SUPPLIED BY THE DIETThe body must have these to grow new tissue

and maintain its health

The essential AA’s are as follows:

Isoleucine (eye-suh-LOO-seen)Leucine (LOO-seen)Lysine (LYE-Seen)Methionine (muh-THIGH-Uh-neen)Phenylalanine (fen-ul-AL-uh-neen)Threonin (THREE-uh-neen)Tryptophan (TRIP-tuh-fan)Valine (VAY-leen)

Histidine (HISS-tuh-deen)*Because histidine is essential only for children, some

scientist don’t consider it an essential amino acid.

Foods that contain all eight essential AA’s are called complete proteinsMost of these sources come from animal

products, with the soybean plant also added to the list

Foods that are short of one or more of the essential AA’s are called incomplete proteinsMost of these are found in grains and

vegetables Combining these will create an essential AA

(examples):Whole wheat bread and peanut butterRice and red beansRefried beans and corn tortillas

High sources of protein in the diet would be considered…EggsMeatFish Poultry

Legumes provide some protein as well

Eggs contain almost every vitamin and mineral you need.

Eggs lack Vitamin C and Calcium. (calcium is found in the shell)

Protein is the foundation of an egg.

Draw Figure 17-7 on page 262 of the “Food Science” Book.

We are considering “Meat” the edible portion of mammals

Muscle tissue (the lean part of meat) is 15-20% protein.

Muscle is composed of fibrous proteins called Actin (AK-tin) and Myosin (MY-uh-sin).

Fish cooks quicker than meat due to less connective tissue.

When cooking fish is usually considered done when it will “flake with a fork”

Carry a rich store of nutrients Cholesterol-free Fat content range from 0-very high

depending on what you are eating. Nuts are usually too high in fat to be a main

source of protein.

Soybeans are composed of 40% protein = to animal protein. High in fiber High in polyunsaturated fatty acids May reduce coronary heart disease Used to create meat substitutes

Denaturation is when the actual nature of the protein is changed.

This usually occurs during food preparation when a protein is heated, agitated, or when chemicals are added to it

The molecules unravel themselves and lose their coiled structure. Creating a looser, less compact structure.

This process is usually not irreversible

Coagulation occurs when a protein is heated. Coagulation is when proteins form clots

Examples include curdling milk to form cheese or cooking an egg.

When a protein is agitated, disrupts the protein structures and causes them to form new positions with other molecules.

When chemicals, such as acids, are added to a proteins, it causes curdling

Both of these processes are used to make new foods (ex; milk to cheese) or to prepare foods (ex; cooking an egg) It is important to remember that

denaturation can be over done (over coagulation), which can cause a change in taste and texture of food. It also can ruin a recipe (ex; over agitation of a meringue will cause clots to form)

*Draw FIGURE 17-6 “Food Science” Book

Page 260

Proteins are used in the preparation of foods in many ways:

Texturize Proteins can be texturized through

denaturationThis process is used to make soybeans

into meat substitutes, or to create processed cheeses

Gelatin - Gelling agents Gelatin protein can be heated in water and then

cooled; or eggs, milk and sugar can be heated to make a custardGeltain provides several benefits:

Structure and support Stabilizer Thickening agent Controls ice crystal growth in frozen foods Gelatin can bind 100 times its weight

Foams – air bubbles incorporated and trapped in a protein film by whipping.

Foam is gas suspended in a liquid or semi solid

Foams can be made using proteins such as eggs or dairy by incorporating air, mechanical agitation or by a sudden release in pressure (aerosol can)

Examples of foams are: Meringues, marshmallows, whipped cream, and bread

Gluten- an elastic substance formed by mixing water with the proteins found in wheat.

It coagulates when baked and forms an airy texture, such as bread.

Gluten is developed as dough is kneaded which mechanically denatures the protein molecules.