Educator's Guide (Grades 9-12) - Buffalo Museum of Science

In the descriptions below, we have only included experiments that are quick to do and are therefore well-suited to
demonstrations. However, it is often unavoidable that results—particularly those relating to protein digestion—can only
be seen after one or several hours (if egg white is used).
EXPERIMENT:
Digestion of Fat
Materials:
Cooking oil, pancreatin, dilute sodium hydroxide, phenolphthalein solution.
Test tubes, beakers, 1 Erlenmeyer flask with airtight stopper,
300ml (or larger), measuring pipette (e.g. 5 ml).
Preparation:
I. Fill each of 2 test tubes with the same amount of water (approx. 5ml).
Put approx. 50 mg (1 “spoon tip’s worth”) of pancreatin into one of these test tubes and shake into a suspension.
II. Put approx. 200 ml of water and approx. 2ml of cooking oil into an Erlenmeyer flask.
Seal the flask and shake it vigorously until an opaque milky liquid forms.
Add 5 drops of dilute sodium hydroxide and 5 drops of phenolphthalein solution to this emulsion,
while swirling the flask. The liquid is now a pink colour .
Method:
Divide the fat emulsion (II) equally between 2 beakers.
Add the pancreatin suspension (I) to one of the beakers.
For comparison, add only an equivalent amount of water to the second beaker .
Observations:
After a short time the contents of the fi rst beaker become colourless, whereas no change can be seen
in the second beaker .
Explanation:
Pancreatin contains the enzyme lipase, which breaks up fat. The free fatty acids that result from the process neutralise
the sodium hydroxide. In neutral and acidic conditions, phenolphthalein is colourless.
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