either be different or all the same. Any of a large number of R groups can be attached, so any of the
three glycerol carbon atoms, so there is an amazingly large number of possible triglycerides.
For example, some of the triglycerides in olive oil are of the following form:
The carbon atoms in the R chains can be attached to each other either with double bonds (C=C), or
with single bonds (C-C). This will determine whether a fat is solid or liquid at room temperature.
Classification of fats
Fats that contain no double bonds in any of their R chains are referred to as saturated fats. They are
called “saturated” because they contain as many hydrogen atoms as they possibly can. These fats
tend to be solids at room temperature, and come from animal sources (for example animal fat and
Unsaturated fats, in contrast, do contain double bonds in their structure. They are unsaturated
because they do not contain as many hydrogen atoms as they could. They tend to be liquid at room
temperature and normally come from plants and fish. They are usually called “the oils”. Unsaturated
fats can be further classified according to their number of double bonds:
· Monounsaturated fats contain only one or few double bonds along their R chains, so they
can accommodate at least one more hydrogen atom. These types of fats include olive oil and
· Polyunsaturated fats, however, contain many double bonds, so can accommodate many
more hydrogen atoms in their structure. These types of fats include sunflower oil and corn oil.
Caution needs to be taken with these polyunsaturated fats because they are likely to become
rancid at room temperature.
Although both the mono and the polyunsaturated fats are liquid at room temperature, the
monosaturated fats, because of their high proportion of saturated fats, will turn cloudy and start to
solidify at refrigeration temperatures because the areas of saturated fats contained in the structure will
begin to congeal.
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Hydrogen atoms can be artificially added to polyunsaturated oils in a process called hydrogenation.