Experiment of the Week - Fat Finding - 4/27/09
a few people wrote favorable comments for last week's experiment, so I
thought we would continue to explore the science of one of my favorite
subjects, food. This time, instead of looking for acids, we are
in search of fats. This test does not require you to taste the
but that doesn't mean you can't have a snack along the way. To
some fats, you will need:
paper bags (This will work with
typing paper, but it does not show up as well.)
- a pen or
- a variety
- cooking oil
by cutting the paper bag into pieces about three inches square.
don't have to be exact. Once you have at least ten or fifteen
of brown paper, its time to head for the kitchen.
we start foraging....I mean rummaging through the refrigerator, lets
get an idea of what we are doing. Place two of your paper squares
the kitchen counter. In the center of one square, put a drop of
water. Use your finger to smear the water around the paper.
that piece of paper "water."
center of the other square, put a
drop of cooking oil, and smear it around too. Label that paper
both pieces of paper up between your eyes and a light source, and you
will see that the wet spots look brighter than the rest of the
The liquid transmits the light through the paper.
place the two pieces of paper on the kitchen counter, and let them sit
for about thirty minutes. That should give you plenty of time to
a nice bowl of ice cream, especially if you use part of the time
slicing bananas and nuts to go with the chocolate sauce, and the
....well, you get the idea.
thirty minutes, check the pieces of paper. The water has probably
evaporated, so if you hold that paper up to the light, it will no
longer have that bright spot where the liquid was. On the other
fats evaporate MUCH slower, so you should still see that bright spot
when you hold the cooking oil spot up to the light.
is how we will test for fats. For each square, we will rub some
food into a spot, label the paper, and then let it sit long enough for
the water to evaporate away. If that food contains fat or oil,
will still be able to see that light spot when you hold the paper up to
now you are ready to start testing foods, but first a couple of words
of warning. Wash your hands well before you begin, use small food
samples, and don't put the food sample back into the
one will want to eat the bit of food that you have been experimenting
with. Do not experiment on those nice steaks, or any other
foods, unless you ask for permission first.
so which foods do you think will contain fats and oils? Some are
obvious. Meats contain fat, so that one is easy. Fats and
contain lots of stored, chemical energy. When an animal eats more
energy (calories) than they need, their bodies store some of that
energy as fat.
contains a LOT of fat. And
where does butter come from? Milk, right? (See the Making
That fat makes milk a very good food for young mammals. Look at
other things that are made from milk, such as cheese and yogurt, as
they should contain fats too. You might want to compare regular
with fat-free yogurt.
move beyond the animal world, and look at some of the plant materials
in your kitchen. A good place to look for plant fats and oils is
seeds, where the oils provide energy for the young sprout. But do
have any seeds in your kitchen? Probably so. Nuts,
are seeds. If you happen to have some peanuts, rub one of them
on one of your paper squares, and you should get a nice oil spot.
you don't have any whole peanuts, try a tiny bit of peanut
aware that some people are very allergic to peanuts.
about other things made from seeds? If you have any mustard in
refrigerator, test it. Mustard is made from mustard seeds.
also have oils added to it, to help dissolve some of the flavor rich
chemicals. While you are testing condiments, mayonnaise also
oils, as do most salad dressings.
part of your fat finding, keep in mind where the fat came from, and
remember that fats and oils are a way for living things to store
energy. That stored energy explains why so many of the
foods in your
kitchen contain those fats and oils, including that bowl of ice cream,
the chocolate sauce, and even the banana peel, which makes that yummy
snack part of a great science experiment.