Transcript FCS-FS-8. Students will discuss why proteins are important in food

a.
b.
c.
d.
e.
Describe ways in which protein is used
in food preparation.
Identify the essential and nonessential
amino acids.
Compare and contrast complete and
incomplete proteins.
Explain what happens during the
denaturation of protein and how the
process occurs.
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 products

Primary 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 following
Hydrogen
 Carbon
 Oxygen
 Nitrogen
 Sometimes 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 acids

There 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-essential

There 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 DIET
 The 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)




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
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*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 proteins

Most 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 proteins

Most of these are found in grains and vegetables

Combining these will create an essential AA
(examples):
 Whole wheat bread and peanut butter
 Rice and red beans
 Refried beans and corn tortillas
High
sources of protein in the diet
would be considered…
 Eggs
 Meat
 Fish
 Poultry
Legumes
well
provide some protein as
 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.

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
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
denaturation
 This 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 custard
 Geltain provides several benefits:





Structure and support
Stabilizer
Thickening agent
Controls ice crystal growth in frozen foods
Gelatin can bind 100 times its weight

Emulsifiers

An emulsion is a stable mixture of a fat and a water
based liquid
 An emulsifier is a molecule that has a polar end and
a non polar end and require heat or mechanical
action to denature and form the emulsion

Egg yolks are an excellent emulsifier, as is milk and
cheese
 Food products such as ice cream and mayonnaise
require emulsifiers to stay together

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.