Iodine is an indicator of starch content in foods. Carbohydrates, being the basis of human nutrition, not all contain starch.
To determine if starch is contained in a particular product, it is enough to apply a few drops of iodine solution to a fresh cut. The appearance of blue indicates the presence of starch in it. Moreover, the intensity of coloring allows you to compare which of the carbohydrates contains more starch. So, potatoes, bread, corn will give a bright blue color. And the banana turns blue.
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