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Unit
Food Science
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Problem Area
Handling and Storing PlantProducts
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Lesson
Oxidative Rancidity
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Student Learning Objectives
1. Explain why food packaging is a critical
component for the food industry.
2. Explain what rancidity is and why rancidity is
a problem to the food industry and consumers.
3. Explain the presence of off-flavors in food
products caused by oxidative rancidity.
4. Explain various practices that limit or stopoxidative
rancidity in foods.
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Terms
Antioxidants
Fatty acids
Glycerol
Hydrolytic rancidity
Oxidation
Oxidative rancidity
Rancidity
Saturated fatty acid
Unsaturated (polyunsaturated) fatty acids
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Why is food packaging a critical component for the food
industry?
Food packaging is critical to food preservation. The
purpose is to protect foods from light, microbial
contamination, chemical changes, and physical damage.
A. Food packaging can be made from a variety ofdifferent
materials.
1. Rigid and flexible metals can be made into cans, drums,
and aluminum foil.
2. Flexible plastics can be turned into a wide variety of
containers.
3. Paper, cardboard, and other wood products can be
turned into boxes and bags.
4. Containers made from laminates or multiple layers can
be created from any of the above sources.
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B. Packaging machinery and equipment must also be
very unique and precise. Equipment must be careful to
not contaminate, crush, or otherwise harm food
products.
C. Food packages must be strong enough to withstand
high heat and cold, sterilization, and for highly
convenient foods final cooking.
D. Food packages must meet stringent guidelines for
flexibility, permeability, burst strength, stretch and other
qualities.
E. Characteristics of good packaging materials include
non-toxic, odorless, flexibility, pliable, puncture
resistant,
good tensile strength at varying temperatures,
permeability, low transmission of vapor, easy
identification, grease proof, stain proof, good sealing,
and easy stripping for the consumer.
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What is rancidity and why is it a problem?
Rancidi ty is the condition reached in certain foods as
the lipid material (fat) undergoes oxidation reactions
producing aldehydes, hydroxyl acids, keta acids, and
other compounds which are responsible for the odor and
off-flavor producing stale foods. An oxygen ion isreplaced with
a hydrogen ion in the fatty acid.
A. Foods that are high in lipids and might become rancid
include potato chips, peanut butter, crackers, and others.
B. Light, oxygen, trace elements such as iron and zinc,
salt, water, bacteria, and molds are factors that speed up
the oxidation process.
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What causes the off-flavors and odors in foods caused
by oxidative rancidity?
There are two types of rancidity.
A. Hydro lyt ic Ranc idi ty is caused by a
breakdown of the fat into glycerol and fatty acid.1. Fatty acids
are organic compounds
containing carbon, hydrogen, and oxygen that
combine with glycerol to make a lipid.
2. Glycerol is the storage form of fat in animals.
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B. Oxidat ive Ranc idi ty results from oxidation of
unsaturated and polyunsaturated fatty acids
producing undesirable flavors and odors.1. Oxidat ion is when a
chemical reaction occurs
forming oxides by reacting with oxygen in the air.
2. Saturated fatty acids are fatty acid molecules
containing no double bonds between carbon atomsthemolecule is
saturated with hydrogen atoms. Saturated
fatty acids are the bad cholesterol.
3. Unsaturated (po lyunsaturated) fatty acids are fatty
acid molecules containing double bonds betweencarbon atomsplant
oils are unsaturated. These are
considered the good fats. Unsaturated fats are more
susceptible to oxidative rancidity than saturated fatty
acids.
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What practices are used for controlling oxidative
rancidity?
A. Adding ant iox idantsAntioxidants are
substances that are added to some foods to
slow down oxidative deterioration.
1. BHAbutylated hydroxyanisole2. BHTbutylated hydroxytoluane
B. Package food protected from light because
light accelerates oxidation.
C. Vacuum packaging to keep oxygen out
because oxygen accelerates oxidation.
However, this process is too costly for most
potato chip manufacturers.
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D. Adding nitrogen to the bag to replace the oxygen.
E. Speed up distribution to shorten the time fromprocessing to
consumption.
F. Shelf dating products allows for consumers to know
when to use food products. Factors that affect the
storage life of a perishable food include:1. length of
storage
2. temperature
3. relative humidity
4. light
G. Vitamin E and Vitamin C also slow oxidative rancidity.
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Review/Summary
Why is food packaging a critical
component for the food industry?
What is rancidity and why is it a problem?What causes the
off-flavors and odors in
foods caused by oxidative rancidity?
What practices are used for controllingoxidative rancidity?
