Home School Life Journal From Preschool to High School

Home School Life Journal ........... Ceramics by Katie Bergenholtz
"Let us strive to make each moment beautiful."
Saint Francis DeSales

Chemistry: Starch Testing

Sam (age 10) tests an apple slice, which stays brown, and a mini marshmallow, which turns black.

Sam (age 10) tested several food items. Most of the results turned out as he expected, but he was surprised that peanut butter tested positive for the presence of starch.

Starches or carbohydrates can be detected easily with an iodine solution. Most drugstores carry "tincture of iodine" which contains iodine and alcohol, which can be used for this experiment.  If the iodine turns black or blue, there is starch present. If it remains reddish brown, there is no a significant amount of starch. Obviously once the food has had iodine on it, it must be discarded and cannot be eaten. Bread, pasta, potatoes and fruit such as bananas and apples all contain starches, and therefore are good things to test, but make sure you also have things that do not have starch so they can compare them. Have them look around your kitchen for things to test.
For upper-level students, you can tell them that iodine specifically detects polysaccharides and will not pick up mono or discaccharides.


  1. Ok, so I wasn't reading your blog at this point, so now I'm wondering if you did this again since 2008, or maybe it was your mystery series where you first talked about this and gave me the idea.

    1. Oh, yes. This is the time I did it with Sam. I have done it with James and Quentin since then. I probably included it in Our Weekly Homeschool Report, or maybe there is another post on this floating around somewhere. LOL


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