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Does heat or time change the starch content of food?

Chapter 8 in the Chemistry Level I text discusses energy molecules, including starches. The corresponding Laboratory Manual experiment uses iodine to test for color changes that vary by the food being tested and the “control” starch sample. But does time or heat change the presence of starch within certain foods?

The variations suggested below will allow your students to observe if the process of cooking or over-ripening has an effect on starch content.

I. Think and discuss.
Students should create new “objectives” and “hypotheses” for the materials to be tested after reading the variations suggested below.

II. Observe it.

A. Set up the experiment “control” as you did for the original Lab Manual experiment.
B. Now, drop the iodine some fruit that has become overly ripe. Do you get the same result if you drop iodine on fruit that is not yet ripe?
C. What happens if you drop iodine on baked potatoes or boiled potatoes or cooked carrots?

III. What happened?
Have your students add any of these varied foods that they test to their Results list in their Lab Manual and record the color changes (if any).

IV. What next?
Are there conclusions the students can draw from their experiments? Make sure to be factual and specific so they are valid conclusions.

Can they apply what they are learning about separating color mixtures to how colors can be combined in art? Help them see how chromatography in science is interrelated to pigments made for use in art and how they can make even more color mixtures when they paint or color.

What did you find to be the most interesting observations made by your student? Did any of the questions or conclusions surprise you? Do you feel he or she is making a connection with how science affects every part of our modern life? Feel free to send us a response with the most interesting entries in their Lab book or your comments about what impact these experiments have.