Why does the flesh turn red after apples are peeled

Apples contain a lot of iron, which is oxidized when exposed to air, iron oxide is reddish-brown, iron hydroxide is reddish-brown, but it is harmless to the body and can be eaten.

In addition to what they say, another important reason is that apples are a fruit rich in divalent ferrous ions, and when it's peeled, the ferrous ions quickly oxidize with the oxygen in the air to form trivalent rust, which is why it's this rusty red color.

Apples will go bad if they last a long time, right? This is the decomposer (bacteria) who thinks that the dead body will rot Before you peel it, you have the peel of the apple to protect the pulp, which slows down the decomposition of the pulp by bacteria, and when you peel it, the pulp leaks into the air and is eroded by a lot of bacteria, and when it heats, it's harmless. The first scientist to discover bacteria saw that the world was full of bacteria, and in the end he starved to death. The other main reason is oxygen, which oxidizes the pulp, just like iron oxide.

Apples contain a lot of vitamin C, also known as L-ascorbic acid, which is an antioxidant that is very easily oxidized, apples are wrapped in the skin, and once cut or bitten, the vitamin C in its juice will be quickly oxidized to oxidized vitamin C, which has a color.

My "100,000 Whys" talks about this problem, but it's actually very simple, because there is a substance called tannins in apples, which "rusts" when it comes into contact with the air. There are also eggplants in them. Just soak in water and you're good to go.

In the local dialect, it is rusted, but it is actually oxidized, and the oxidized apples are not delicious, so don't eat them!

The fructose in apples oxidizes in the air.

The flesh turns red when the apple is peeled due to the oxidation reaction between the flesh and the air.

After the apple is picked from the tree, it is like a child leaving its mother, but the phenols in its body will continue to maintain its own respiration, but once peeled, the phenols will be oxidized and decomposed by oxides in the air under the action of phenols, and quinones will be formed, a process called enzymatic browning.

Enzymatic browning mostly occurs in fresh plant foods such as fruits and vegetables, and is the result of phenolases-catalyzed phenolic substances forming quinones and their polymers. The result is that the epidermis turns yellowish-brown, and some of the corresponding nutrients are decomposed, but it is still edible.

01 After the apple is peeled, the phenolic substances in the plant cells are oxidized with the air under the action of phenolase, producing a large number of quinones. The new quinones can cause plant cells to turn brown quickly, a change called enzymatic browning of food, so apples will change color when peeled.

It turns out that apples are still respiring after they are picked from the tree, which is the effect of phenols in apples. When the apple is peeled, the apple pulp is exposed to oxygen in the air, and this phenolic enzyme is oxidized, producing a large amount of quinones. In this way, phenol, which was previously colorless, becomes brown, so the whole apple also changes color.

As a result, not only will the sugar content of the apples be reduced, but the newly formed ingredients will also make the apples taste and soften.

The discoloration reaction occurs mainly due to the presence of phenolic compounds in these plants. For example: polyphenols, catechols, etc.

Phenolic compounds are easily oxidized to quinones, that is, they change color and turn yellow, and the color gradually deepens with the increase of the amount of reaction, and finally turns dark brown. The oxidation reaction occurs due to the contact with oxygen in the air and the release of phenol oxidase in the cell.

Phenolic oxidase exists in organelles and cannot come into contact with phenolic compounds until the tissue is damaged, and oxygen in the air cannot enter, so no oxidative discoloration reaction occurs. When the cell tissue is damaged, phenol oxidase is released to contact with phenolic compounds, catalyzing the oxidation of phenolic compounds, coupled with the action of oxygen in the air, a discoloration reaction will occur.

Among them, polyphenols can be directly oxidized to quinones and change color. Catechol molecules, on the other hand, polymerize under the action of phenol oxidase. Two catechol molecules are linked together to form catechol dimers, which in turn can be joined in pairs to form tetramers.

The individual catechol molecules and their dimers and tetramers are all colorless, but catechol tetramers can form multimers, which are purple. So the more polymers are formed, the darker the color of the incision surface will be.

When apples change color, the amount of vitamin C will decrease, affecting the nutritional value. To prevent the apple from changing color after cutting, the best way to keep it out of contact with the air is to soak the apple in salt water.