The blackening of lotus root in iron pot is related to the polyphenols contained in it. These guys have the same property, that is, they can combine with iron ions to form purple or blue colored complexes. Gallic acid is one of the abundant polyphenols in lotus root, which combines with iron ions to form a blue-black substance, which is the main component of blue-black ink. No wonder sparerib soup can be made into ink soup.

The secret of lotus root turning into ink in iron pot has been found, but why does lotus root turn black when it is put in the vegetable basket without any iron? This is because the polyphenols in lotus root mentioned above are in

Under the action of polyphenol oxidase (PPO), it is oxidized into chemicals called "quinones", and these quinones are polymerized together to form melanin. In fact, the cut apple will turn brown and the banana in the refrigerator will turn black.

Black, all for this reason.