Iodine Test
Iodine Test is a way to check if food contains starch by watching for a dark color change.
A small brown drop goes onto a slice of bread or potato on a plate. The drop changes color based on what is in the food. If starch is there, the brown drop turns dark purple or black right away. If there is no starch, the drop stays light brown.
Explaining iodine test by grade level
Put a drop of brown iodine on a slice of potato. The brown drop turns dark blue or black. That dark color means the potato has starch in it. Foods like rice and flour turn dark too, but an apple stays the same light brown.
Projects that explore iodine test
Iodine solution turns dark brown or blue-black when it touches starch, making it a simple detector. When you apply a few drops to samples like raw potato and flour, the color change appears within seconds. Butter and salt, which contain no starch, show no change at all.
This project uses iodine spray to track how starch levels inside apples change at different storage temperatures. You cut apples in half horizontally and spray the exposed flesh with iodine solution. Darker color means more starch remains. As storage temperature rises — from 4 degrees C to 21 to 32 degrees C — apples ripen faster, and both starch and malic acid break down more quickly. That means the iodine color stays lighter in apples stored at higher temperatures.