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© 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.
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 3
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.
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 4
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.
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 5
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
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 6
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.
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 7
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
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 8
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
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 9
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
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 10
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
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 11
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.
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 12
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.
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 13
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
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 14
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.
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 15
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.
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 16
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.
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 17
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
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 18
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.
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 19
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)
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 20
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).
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 21
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.
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 22
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
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 23
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
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 24
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
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 25
Questions?
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 26
Activity
• I Second That Emulsion
• Baffling Beaters
• Alginate Gummies
Photos courtesy of Peter Machado, University of Maryland
© 2007 Institute of Food Technologists© 2007 Institute of Food Technologists 27
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.
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