run something into something. 1. to guide or route something, such as a wire or a pipe, into something or a place. The worker ran the circuit into each room. He ran in the circuit as specified. 2. to guide something into something; to drive or steer something into something else.
A change of color to a blue-black or purple color suggests that starch is present. If there is no change in color, this suggests no starch is detectable. Note the change of the iodine to black on the potato (right) but not the apple (left). (10% Tincture of iodine.) Potato contains starch, but apple does not.
When iodine is added to a starch, it adheres to the beta amylose molecules because of their solubility. The starch pushes the iodine into a line in the middle of the amylose coils and creates a transfer of charge between the iodine and starch. This causes a change in the arrangement of electrons and energy level spacings. The new spacings absorb visible light differently and create the deep blue color. Iodine is often used to test foods for starch. Adding iodine to potatoes, dried beans, rice, bread and pasta creates the deep blue reaction to indicate the presence of starch. To perform the test, use a dropper to add one or two drops of iodine to each type of food. Use other foods that do not contain starch, such as apple slices, carrots and sugar, for comparison.