Question

How do you test for starch?

Answer 1

The most used test for starch is iodine.

Explanation:

Iodine forms a dark-blue complex with starch, at normal temperatures. Usually the iodine is dissolved in a solution of potassium iodide (`K^+I^-`) to form the complex ion `I_3^-`, because iodine doesn't dissolve well in water.
Sometimes it's dissolved in alcohol.

Answer 2

Use an iodine solution.

Explanation:

Iodine is an effective tool to test for starch. At normal conditions, it is usually brown, while in the presence of starch, it turns blue-black. See this picture of the test: