Kids, we have cooked up a treat for you just in time for Thanksgiving.  This activity will involve the baking of an unusual apple pie, one that needs no actual apples.  It tastes and looks like apple pie because some tricks of chemistry are used to reproduce the taste of apples, and other ingredients are used to resemble the look and texture of apples.  The classic recipe for this (“Mock Apple Pie”) can be found on the back of a box of Ritz™ crackers.   There are also a few slightly different recipes available on the internet (see the links below for “Chemical Pies”). 

Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

The classic recipe is repeated here.  You will need: two 9-inch pre-made pie crusts, 36 Ritz™ crackers (coarsely broken up), 1-3/4 cups water (H₂O), 2 cups sugar (sucrose, C₁₂H₂₂O₁₁), 2 teaspoons cream of tartar (potassium bitartrate or potassium hydrogen tartrate, KC₄H₅O₆ or KO₂CCH(OH)CH(OH)CO₂H; these are all the same thing!), 2 tablespoons lemon juice and the grated peel of one lemon, 2 tablespoons margarine or butter, and 1/2 teaspoon ground cinnamon.   Step 1. Line a 9-inch pie plate with one pastry shell.  Place cracker crumbs in the shell and set aside.  Step 2. Have an adult partner heat the water, sugar and cream of tartar to a boil in a saucepan and then simmer for 15 minutes.   Add the lemon juice and peel, then let it cool.  Step 3. When cooled, pour the syrup over the cracker crumbs.  Dot with margarine or butter and sprinkle with cinnamon.  Cover with the remaining pie shell.  Slit top crust to allow steam to escape.  Step 4. Bake at 425oF for 30 to 35 minutes.  Cool completely and enjoy eating your experiment.

If you were to give a piece of this pie to an unknowing friend or relative telling them that it is apple pie, chances are that they will eat it, like it, and never know the difference.  Why does this work so well?  The cream of tartar produces a weak acid which, when combined with the other ingredients, produces the tangy taste of apples.  The pieces of cracker closely resemble the texture and appearance of apple pie.  Our senses of taste and smell are then tricked into thinking that it is, indeed, apple pie.  Because our senses can be easily tricked this way, as scientists we must use sensitive instruments to accurately measure and identify substances and the changes that occur around us.

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Kathleen Carrado Gregar, PhD, Argonne National Labs 
[email protected]
November 2004

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References:

http://www.backofthebox.com/recipes/pies-pastries/ritz-mock-apple-pie.html
http://collections.ic.gc.ca/science/english/chem/projects/artifical.html
http://www.geocities.com/CapeCanaveral/Hall/1410/lab-Food-04.html
http://www.usoe.k12.ut.us/curr/science/sciber00/8th/matter/sciber/chempie.htm