© 2007 Institute of Food Technologists The Science of Food Speaker Name Speaker Title Date...

© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists

The Science of FoodThe Science of Food

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© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 2

What is Food Science?

Food Science is the discipline in which

biology, physical sciences, and

engineering are used to study the nature

of foods, the causes of their deterioration,

and the principles underlying food

processing.


What is Food Technology?

Food Technology is the

application of food science to

the selection, preservation,

processing, packaging,

distribution, and use of safe,

nutritious, and wholesome

food.


What does a Food Scientist do?

A Food Scientist studies the physical, microbiological, and

chemical makeup of food. Depending on their area of

specialization, Food Scientists may develop ways to

process, preserve, package, or store food, according to

industry and government specifications and regulations.


The science of food

• Food Chemistry is the study of: The composition of raw materials in foods The composition of the end-products of food

production The changes which occur in food during its

production, processing, storage and cooking

• Examples of the science of food in everyday life: Emulsions: Butter, ice cream, milk, mayonnaise Foams: Ice cream, marshmallows, whipped

cream, meringue Gels: Gelatin desserts, Pimento’s in olives,

pudding, gummy candies


Emulsions

• Oil and water don’t mix!

• But we are surrounded by foods

that are made by mixing oil and

water.

• Salad dressing, butter, ice cream,

and milk are all oil-in-water

mixtures that don’t separate

under normal conditions.

• So how can we explain this?

• All of these foods are emulsions.


Emulsions

• An emulsion is a colloid in which

liquids that do not normally mix are

spread throughout each other.

• Emulsifying is done by slowly

adding one ingredient to another

while simultaneously mixing. This

disperses and suspends tiny

droplets of one liquid (known as

the dispersed phase) through

another (known as the continuous

phase).

A colloid is a mixture of very tiny particles that are dispersed in another substance but do not settle out of that substance

Oil

Water

DispersedPhase

ContinuousPhase


Emulsions• To prevent the mixture from

separating, an ingredient, known as

an emulsifier, which is attracted to

both oil and water, is added, thus

allowing the two to mix.

• The emulsifier functions by

surrounding the oil droplets to form

a protective coat which holds the oil

droplets in suspension.

• One part of the emulsifier molecule

(the polar end) is soluble in water

and one part is soluble in the oil

(the non-polar end).

Oil

Non-polarendPolar

end

Water


Mayonnaise

• Mayonnaise is an example of an oil-in-vinegar emulsion.

• The basic ingredients in mayonnaise are: Large quantities of oil (dispersed phase) Small quantities of an acid (continuous phase), such as vinegar or

lemon juice, and Egg yolk (the emulsifier) Other ingredients may be added for flavor


Mayonnaise• The egg yolk is added because it

contains lecithin (phosphatidyl choline), a naturally occurring emulsifier.

• The lecithin functions by surrounding the oil droplets to form a protective coat which holds the oil droplets in suspension.

• One part of the lecithin molecule (the polar end) is soluble in water and one part is soluble in the oil (the non-polar end). Since lecithin is attracted to both the oil and the water it prevents them from separating.

Polar End

Non-Polar End


Foams

• A foam is a type of colloidal

dispersion in which very tiny

particles of gas are dispersed

(scattered) in a liquid or solid

substance and do not settle out of

that substance.

• Examples of foods that are

considered foams include ice

cream, whipped cream, foamed

milk, marshmallows, and beaten

egg white.


Foams• A foam is made by agitating a liquid (by beating or mixing) which in turn traps air inside the liquid film.

• As air is trapped in the liquid the dispersion increases in volume.

• This increase in volume is known as overrun.


Egg White Foam

• Egg white foam is a type of foam used in meringues,

soufflés, foamy omelets, angel food cake, and sponge

cakes to make them light and porous (airy).

• An egg white foam is a colloid of bubbles of air

surrounded by part of the egg white protein (albumen)

that has been denatured during beating.

Denaturation is the change of a protein’s shape under stress


Egg White Foam: Preparation• To prepare an egg white foam, egg

whites are initially beaten (with a wire wisk or electric mixer) until they become frothy.

• Then an acid (such as cream of tarter) and salt are added.

• These ingredients are not added at the beginning because they delay foam formation.

• The beating of the egg white foam then continues.

• The foam increases in volume and the air bubbles become smaller and more evenly distributed.


Egg White Foam: Preparation

• Several factors affect the formation and stability of egg white

foams. These include: Fat: The addition of even a small amount of fat will interfere with the

formation of a foam. Fat is present in the egg yolk so it is very

important that all of the egg yolk is separated from the egg white prior

to foam preparation. Salt: Salt is added to egg white foams for flavor. pH: Addition of an acid (such as cream of tarter) will decrease the pH

of the egg white foam to near the isoelectric point of the egg white

proteins. At the isoelectric point, the proteins are least stable and

more sensitive to denaturation.


Egg White Foam: Preparation

• Several factors affect the formation and stability of egg white foams.

These include: Temperature: An egg white foam is formed and reaches greater volume

more quickly when egg whites are at room temperature rather than at

refrigerator temperature. The stability of egg whites beaten at room

temperature, however, is not as great as those beaten at colder

temperatures. Sugar: Sugar is added during foam preparation because it creates a

smooth, stable foam – one that will not collapse and drain quickly (i.e.

syneresis will be delayed). Sugar is believed to contribute to the stability

of the foam because of its ability to hold onto water that might escape

from the foam. Sugar does, however, increase the beating time of an egg

white foam because it delays the denaturation of the egg proteins.


Gels

• Gels are defined as more-or-less rigid colloidal systems

• In the case of gels, solid particles are dispersed in a liquid. The solid particles form a network structure which traps the liquid and gives the gel its shape.

• In food preparation, gels are often formed by the proteins of eggs or flour in such products as puddings, batters, and doughs. Gelatin, a type of protein found in the bone and skin tissue of animals, also forms gels.

• Some types of carbohydrates such as alginate, starch, and pectin, also form gels.

A colloid is a mixture of very tiny particles that are dispersed in another substance but do not settle out of that substance


Alginate Gels• Alginate is a type of polysaccharide

that occurs naturally in all brown

algae as a skeletal component of

their cell walls.

• Alginate is used in food because it is

a powerful thickening, stabilizing,

and gel-forming agent.

• Some foods that may include

alginate are ice cream, fruit-filled

snacks, salad dressings, pudding,

onion rings, and even the pimento

strips that are stuffed into green

olives.

Ingredients: Olives, Water, Minced Pimento (Sodium Alginate, Guar Gum, Calcium Chloride),Salt, Lactic Acid.


Alginate Gels• Most alginate used in foods is in

the form of sodium alginate.

• In order to form a gel, sodium alginate needs to come into contact with divalent ions such as calcium (Ca2+).

• As soon as sodium alginate (Figure 1) is added to a solution of calcium chloride a gel forms as the sodium ions (Na+) are exchanged with calcium ions (Ca2+) and the polymer becomes crosslinked (Figure 2).

CO2- CO2

-

CO2- CO2

-

CO2-

CO2- CO2

- CO2-

CO2- CO2

-

Figure 1. Alginate polymer in NaCl solution(no crosslinking) (Waldman et al. 1998)

Na+

Na+

Na+

Na+

Na+

Na+ Na+ Na+

Na+ Na+

Ca2+

Ca2+

Ca2+

Ca2+

Ca2+

Ca2+

Ca2+

Figure 2. Alginate polymer in CaCl2 solution(crosslinking) (Waldman et al. 1998)


Alginate Gels

• The calcium ions are able to crosslink the alginate polymers

because they can form two bonds, as opposed to

monovalent ions such as sodium which can only form one

bond.

• The longer the alginate is in contact with the calcium

chloride solution, the more rigid the gel will become, as

more crosslinks are formed.

• Also, depending on the concentration of calcium ions, the

gels are either thermoreversible (low concentrations) or not

(high concentrations).


Alginate Gels

• Remeber the pimentos?

• Now, take a closer look at the

ingredients…

Ingredients: Olives, Water, Minced Pimento (Sodium Alginate, Guar Gum, Calcium Chloride),Salt, Lactic Acid.


Careers in Food Chemistry

• Job Titles: Food Chemist Scientist

• Employers: Food processors Ingredient

manufacturers/suppliers Academia (Higher Education) Contract research

laboratories/development firms Self-employed/Consultant

• Responsibilities: Analyze processing and

packaging methods Study effect of processing on the

appearance, taste, aroma,

freshness, and vitamin content of

the food Test samples to make sure

foods meet food safety laws and

experiment with new foods,

additives, and preservatives


Careers in Product Development• Job Titles:

Product Development Scientist Scientist

• Employers: Food processors Ingredient

manufacturers/suppliers Academia (Higher Education) Contract research

laboratories/development firms Self-employed/Consultant

• Responsibilities: Bench-top development Testing Plant scale-up Commercialization Troubleshooting


Want to learn more?

•Visit: http://www.ift.org http://school.discovery.com/foodscience/

•Find a Food Scientist: A database of IFT members who are willing to

provide more information about the field of food

science to you http://members.ift.org/IFT/Education/TeacherResources/findafoodscientist.htm


Questions?


Activity

• I Second That Emulsion

• Baffling Beaters

• Alginate Gummies

Photos courtesy of Peter Machado, University of Maryland


References• Belitz HD and Grosch W. Food Chemistry. Berlin: Springer, 1999.

• Himich Feeland-Graves, J and Peckham, GC. Foundations of Food Preparation. 6th edition. Prentice Hall: Englewood Cliffs, NJ, 1996.

• Waldman AS, Schechinger L, Govindarajoo G, Nowick JS, and Pignolet LH. 1998. The Alginate Demonstration: Polymers, Food Science, and Ion Exchange. Journal of Chemical Education. 75(11): 1430-1431.

Headquarters525 W. Van Buren StreetSuite 1000Chicago, IL 60607312.782.8424ift.org

Washington, D.C. Office1025 Connecticut Avenue, NWSuite 503Washington, D.C. 20036202.466.5980

© 2007 Institute of Food Technologists The Science of Food Speaker Name Speaker Title Date...

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