WHAT ARE
LIPIDS?
Presentation prepared by
Alice F. Mullis
February 2011
DEFINITION of LIPIDS
• Lipids are a category of organic
compounds that are insoluble in
water and have a greasy feel.
• Contain mostly carbon, hydrogen
and some oxygen.
How do LIPIDS differ from
CARBOHYDRATES?
• They are not polymers (large molecule
that consists of large numbers of small
molecular units, which are linked).
• Do not provide structure to foods.
• Cannot be dissolved in water; they are
non-polar thus they are soluble in organic
compounds.
Why are Lipids important?
• Used to store lots of energy (lipids/fat)
– Lipids more difficult to break down
(metabolize), but store more energy than
carbohydrates
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Form cell membranes (the “skin” of the cell)
Cell communication
Hormones
Many others…
More Lipid information...
• Lipids are an integral part of our daily diet.
• Most oils and milk products that we use for cooking
and eating, like butter, cheese, etc., are composed of
fats. Vegetable oils are rich in various
polyunsaturated fatty acids.
• Lipid-containing foods undergo digestion within the
body and are broken into fatty acids and glycerol,
which are the final degradation products of fats and
lipids.
What do Lipids look like?
• Each molecule has a
“head” with a “tail”
– Tail usually consists of
two or three strands
Cell Membranes of Lipids
• Phospholipids make up cell membranes
• Cell membranes are predominantly
composed of phospholipids and cholesterol.
Cell membranes provide stability to cells
and control entry or release of chemicals
into or from the cell.
– Water is polar
– Phospholipids have polar and non-polar ends
• So water and phospholipids don’t mix well (one end
likes water, the other doesn’t)
What are Lipids?
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Fats
Oils
Shortening
Grease
Phospholipids
Sterols
Cholesterol
GLYCERIDES
Molecules that have a glycerol base are called
glycerides (a type of lipid).
Fatty acids are organic molecules that consist
of a carbon chain with a carboxyl group at
one end.
Fatty Acids + Glycerol = Lipids
Most lipids found in foods and in the body are
triglycerides.
GLYCERIDES continued…
Some glycerides are partially soluble in
water such as mono- and diglycerides.
These are added to processed foods such
as butter and margarine to keep mixtures
of water and fats stable.
PHOSPHOLIPIDS
• A phospholipid is a glycerol base with
two fatty acids and a phosphoruscontaining acid attached.
• Important role in the body - help carry fats
back and forth across cell membranes.
• Important role in food products – help fats
stay mixed in water-based solutions like
mayonnaise (keeps it from separating).
STEROLS
• Sterols are complicated molecules derived
or made from lipids.
• Sterols include:
Cholesterol
Vitamin D
Steroid hormones
CATEGORIES OF LIPIDS
• Saturated – when fatty acids have the
maximum number of hydrogen atoms.
• Unsaturated – if fatty acid does not
contain all the hydrogen atoms it could.
• Monounsaturated – fatty acids that have
one double bond in the carbon chain.
• Polyunsaturated – fatty acids have two or
more double bond bends in the fatty chain.
Why be concerned about
Trans-Fatty Acids?
• Found in many margarines.
• A product of hydrogenating vegetable oil.
• Humans may not be able to digest the
trans-form of these fatty acids & may add
build up in blood vessels.
• More study is required.
PHYSICAL STATE of LIPIDS
• Fats – lipids solid at room temperature
• Oils – lipids liquid at room temperature
• Melting Point – temperature at which a
lipid is completely liquid
• Hydrogenation – process of adding
hydrogen atoms to an unsaturated lipid to
increase its saturation level.
PHYSICAL
CHARACTERISTICS of
LIPIDS
• Three physical characteristics impact
the way lipids perform in food
products:
Melting Point
Solidification Point
Reaction to Oxygen
RESOURCES
Principles of Food Science, Glencoe, 2007. Janet Ward. Chapter 10, pages 216-240.
http://www.bigoven.com/glossary/shortening
http://en.wikipedia.org/wiki/Shortening
http://en.wikipedia.org/wiki/When_You're_Hot,_You're_Hot
http://www.youtube.com/watch?v=Bzewk-FMgS0
http://www.landolakes.com/Products/Butter/
http://www.landolakes.com/TestKitchen/TipsAndTechniques/FAQ/Butter.aspx
http://www.wisegeek.com/what-is-whipped-butter.htm
http://en.wikipedia.org/wiki/Mayonnaise
http://www.brooklynfarmhouse.com/basic-techniques/how-to-make-mayonnaise/
http://www.ask.com/wiki/Condiment
http://en.wikipedia.org/wiki/Biochemistry
http://www.biochemweb.org/lipids_membranes.shtml
http://www.encyclopedia.com/topic/lipids.aspx