Starch in food

Procedure

• Add the food we want to analyze on a plastic dish.
• In the beaker, mix 10 mL of Betadine with 90 mL of distilled water.
• Add a few drops of the diluted Betadine and observe what happens.

Theoretical explanation

Betadine is a solution of iodine in potassium iodide. Iodine is a highly toxic substance due to its oxidizing power and can cause digestive corrosion and irritation of the respiratory tract.

On the other hand, starch is a plant-derived biopolymer. It is composed of many units of glucose (sugar) linked together to form long chains and networks. It is the only one assimilated by the human digestive system and we use it as an energy source. Many foods contain it, but… How do we know which ones?

When Betadine comes into contact with starch, a new compound less toxic of dark blue color is formed. This is why starch is used as an antidote in iodine poisoning. Therefore, if we add Betadine to a food that contains starch, a dark blue color will be observed. However, if the food does not contain starch, the color of the Betadine will remain brown.