Salad cream is a
runny emulsion.
This means it is
mostly water. We
call it an oil in water
emulsion.
Margerine is a thick
emulsion. This
means it is mostly
oil. We call it an
water in oil
emulsion.
It is important that you look at pages 142 and 143 to see the structure of saturated and unsaturated oils
This is another word which pupils tend to find confusing – but really it is so simple.
Lets clear it up: There are two types of vegetable oil – saturated and unsaturated.
Saturated oils cannot accept any more hydrogen (like an alkane). These have high
melting points and are solid at room temp.
Unsaturated oils are like alkenes, they have double bonds and can still accept
hydrogens. This gives them a low melting point and so they are liquid at room temp.
Saturated oils make great tasty
spreads because they are less
runny and can spread very nicely
on your bread.
Unsaturated oils are healthy, but
make rubbish sandwich spreads –
after-all they are so runny your
bread will go soggy!!
The big problem is saturated oils
is that they are less healthy, and
increase cholesterol levels. Too
many will cause heart disease!!
That’s a bad thing!!
We can thicken them up by making
them less unsaturated i.e. by adding
more hydrogen (hydrogenate). This
increases the melting point making
them more solid and therefore more
spreadable!
So, how do we hydrogenate unsaturated vegetable oils???
Unsaturated
oil
60 degrees
Nickel catalyst
Thicker, more
saturated oil.
+ Hydrogen
Some of the oils produced by hydrogenation are called trans-fats.
These are fats which do not occur in nature. As a result the body is
not sure how to deal with them and the result is an increased risk of
heart attacks.
Tans fats – unsurprisingly are commonplace in fast foods!