Amylase and a simple enzyme experiment

When it comes to digestion, chewing is the obvious starting point.  Less obvious however are all the enzymes contained within our saliva that also aid digestion.  Enzymes simply put are chemicals that aid the breakdown of substances, or cause a certain chemical reaction to take place.  In the case of saliva, a particular enzyme called Amylase aids the break down or digestion of carbohydrates and starch, turning them into sugars.  Part of the function of chewing is not only to break our food into smaller pieces but also to mix food thoroughly with amylase so our food is digested more efficiently.  We may have consciously experienced the effects of amylase when eating starchy or carbohydrate rich food and notice that the food becomes slightly sweeter after chewing a while.  This sweet taste is a result of amylase breaking down carbohydrates or starch into sweeter tasting sugars. 

We developed a simple lab experiment demonstrating the effects of amylase that anyone can do with some basic equipment.  This is probably an experiment that others have developed, I just haven't come across it before.  All that is needed is a test tube, chlorine free water, saltine crackers, potassium iodide, and spit.  Tap water can be de-chlorinated by letting it set out for 24 hours and potassium iodide (IKI) and test tubes can be purchased on-line. 

Here are the steps to this experiment:
1. Crush up part of a saltine cracker into a fine powder.  You don't need much, only enough to cover the bottom of a test tube.  (this imitates the effects of chewing)
2. Place the crushed cracker in the bottom of a test tube, you only need enough to cover the bottom.
3. Add an equal amount of de-chlorinated water to the test tube and mix thoroughly.
4. Add one or two drops of potassium iodide (IKI) to the water-cracker mix and mix again thoroughly.  At this point much of the cracker should turn a brown color.  This is a result of the IKI staining starches in the cracker brown.
5. Double (or slightly more) the total volume in the test tube with saliva.  Yes, just let some spit accumulate in your mouth and then spit into the test tube.
6.  Mix and wait to see what happens.

Cracker ground up into fine powder.  A small amount like this works best.  Too much cracker makes the experiment work a lot slower.

Cracker with de-chlorinated water added. 

Cracker and water with an added drop of potassium iodide (IKI).  Notice the darker appearance which is the result of IKI staining starch brown.

Saliva added to the above mixture and let sit for about five minutes.  The amylase in the saliva breaks down the starch into sugar.  When the starch disappears the IKI no longer stays brown but instead clears up.  The lighter color indicates the starch has been digested by amylase in the saliva.  By waiting even longer the solution would clear up even more as more starch is digested into sugar.

In the above experiment, as amylase within the saliva breaks down starch into sugar the brown color disappears.  This experiment can be modified to see if heated or cooled saliva will still make the starch disappear.  Chemicals such as vinegar or baking soda could be added, or other foods tested out.